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1
Libera, Matthew R. "AEM analysis of solidification catalysts in atomized Fe-Ni." Proceedings, annual meeting, Electron Microscopy Society of America 44 (August 1986): 584–85. http://dx.doi.org/10.1017/s0424820100144395.
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The liquid droplets produced by atomization processes are believed to undergo substantial supercooling during solidification, because the catalytic heterogeneities, for statistical reasons, tend to be isolated in the larger droplets. This supercooling can lead to the nucleation of metastable phases. As part of a study on the effect of liquid supercooling on nonequilibrium solidification, three binary Fe-Ni alloys have been produced by conventional argon atomization (Fe-20Ni, Fe-30Ni, and Fe-40Ni). The primary variables in these experiments are: i) the alloy composition; and ii) the powder particle diameter (inversely proportional to supercooling). Of particular interest in this system is the competitive nucleation kinetics between the stable fee and metastable bec phases. Bcc is expected to nucleate preferentially with decreasing %Ni and decreasing particle diameter.
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Wang, Zhi Gang, Jun Xu, Bao Li, and Zhi Feng Zhang. "Study on Refinement Mechanism of Sc and Zr as-Cast Al-7.2Zn-2.2Mg-1.8Cu Alloys." Applied Mechanics and Materials 372 (August 2013): 66–69. http://dx.doi.org/10.4028/www.scientific.net/amm.372.66.
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The effect of trace Sc and Zr on grain refinement of Al-7.2Zn-2.2Mg-1.8Cu as-cast ingot was studied by using optical microscopy and scanning electron microscopy with EDS. The results show that addition of only 0.20% Zr or 0. 20% Sc to Al-7.2Zn-2.2Mg-1.8Cu alloy can refine grains to a certain degree, and the addition of 0.10% Sc+0.20%Zr leads to stronger grain refinement, the average grain size is only 10-15μm. Al3Sc/Al3Zr composite particles in the melt work as the nucleation of heterogeneous nucleation during solidification.
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Kooi, Bart J., R. Pandian, J. Th M. De Hosson, and Andrew Pauza. "In situ Transmission Electron Microscopy Study of the Crystallization of Fast-growth Doped SbxTe Alloy Films." Journal of Materials Research 20, no. 7 (July 1, 2005): 1825–35. http://dx.doi.org/10.1557/jmr.2005.0228.
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Crystallization of amorphous thin films composed of doped SbxTe with x = 3.0, 3.6, and 4.2 and constant dopant level was studied by in situ heating in a transmission electron microscopy. Magnetron sputtering was used to deposit 20-nm-thick films sandwiched between two types of 3-nm-thick dielectric layers on 25-nm-thick silicon-nitride membranes. One type of dielectric layer consists of ZnS–SiO2 (ZSO), the other of GeCrN (GCN). Crystallization was studied for temperatures in-between 150 and 190 °C. The type of dielectric layer turned out to strongly influence the crystallization process. Not only did the nucleation rate appear to depend sensitively on the dielectric layer type, but also the growth rate. The velocity of the crystalline/amorphous interface is about 5 times higher for the x = 4.2 film than for the x = 3.0 film if ZSO is used. In case of GCN, the interface velocity is about 2 times higher for the x = 4.2 film than for the x = 3.0 film. The activation energy for crystal growth is not significantly dependent on the Sb/Te ratio but is clearly different for ZSO and GCN—2.9 eV and 2.0 eV, respectively. The incubation time for the crystal nuclei formation is longer for ZSO than for GCN. Although the effects of the Sb/Te ratio and the dielectric layer type on the growth rates are strong, their effects on the nucleation rate are even more pronounced. A higher Sb/Te ratio results in a lower nucleation rate and the use of GCN instead of ZSO leads to higher nucleation rates.
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Liu, Han Min, Jie Cheng, Yue Hua Wen, Jun Li Pan, and Gao Ping Cao. "Study of Substrate for the Zinc Electrode in Acid Zn-PbO2 Flow Battery." Applied Mechanics and Materials 700 (December 2014): 136–40. http://dx.doi.org/10.4028/www.scientific.net/amm.700.136.
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An investigation into the suitability of carbon materials, metallic lead and its alloys as substrates for the zinc electrode in acid Zn-PbO2 flow batteries was performed. No maximum current appears on the potentiostatic current transients recorded for the zinc deposition on the lead and its alloys. With increasing the overpotential, the progressive nucleation turns to be the 3D-instantaneous nucleation process employed for the resin-graphite composite. Hydrogen evolution on the graphite composite is effectively suppressed due to the doping of polymer resins. The rate of hydrogen evolution reaction on the lead is relatively weak, but on the lead alloys, the hydrogen evolution conversely becomes serious to a certain degree. Though the exchange current density of the zinc deposition and dissolution process on the graphite composite is relatively low, the zinc corrosion is weakened to a great extent. With the increase of deposition time, the zinc deposits tend to be more compact. Zinc galvanostatic charge-discharge cycling on the graphite composite reveals that the coulombic of over 90% can be found, exhibiting an excellent cycling stability.
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Hashim, Aimi Noorliyana, Mohd Arif Anuar Mohd Salleh, Andrei Victor Sandu, Muhammad Mahyiddin Ramli, Khor Chu Yee, Noor Zaimah Mohd Mokhtar, and Jitrin Chaiprapa. "Effect of Ni on the Suppression of Sn Whisker Formation in Sn-0.7Cu Solder Joint." Materials 14, no. 4 (February 5, 2021): 738. http://dx.doi.org/10.3390/ma14040738.
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The evolution of internal compressive stress from the intermetallic compound (IMC) Cu6Sn5 growth is commonly acknowledged as the key inducement initiating the nucleation and growth of tin (Sn) whisker. This study investigates the effect of Sn-0.7Cu-0.05Ni on the nucleation and growth of Sn whisker under continuous mechanical stress induced. The Sn-0.7Cu-0.05Ni solder joint has a noticeable effect of suppression by diminishing the susceptibility of nucleation and growth of Sn whisker. By using a synchrotron micro X-ray fluorescence (µ-XRF) spectroscopy, it was found that a small amount of Ni alters the microstructure of Cu6Sn5 to form a (Cu,Ni)6Sn5 intermetallic layer. The morphology structure of the (Cu,Ni)6Sn5 interfacial intermetallic layer and Sn whisker growth were investigated by scanning electron microscope (SEM) in secondary and backscattered electron imaging mode, which showed that there is a strong correlation between the formation of Sn whisker and the composition of solder alloy. The thickness of the (Cu,Ni)6Sn5 IMC interfacial layer was relatively thinner and more refined, with a continuous fine scallop-shaped IMC interfacial layer, and consequently enhanced a greater incubation period for the nucleation and growth of the Sn whisker. These verification outcomes proposes a scientifically foundation to mitigate Sn whisker growth in lead-free solder joint.
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Wu, Di, and Zhuang Li. "Study on the Machinability of Free Cutting Non-Lead Austenitic Stainless Steels." Advanced Materials Research 430-432 (January 2012): 306–9. http://dx.doi.org/10.4028/www.scientific.net/amr.430-432.306.
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In this paper, a new non-lead machinable austenitic stainless steel was investigated. The metallurgical properties, machinability and mechanical properties of the developed alloy were compared with those of the conventional austenitic stainless steel 321. The results have shown that the presence of machinable additives, such as sulfur, copper and bismuth, etc. contributes to the improvement of the machinability of austenitic stainless steel, because the inclusions are something like internal notches causing crack nucleation and facilitating rupture. Bismuth has a distinct advantage over lead. The machinability of the austenitic stainless steels with free-cutting additives is much better than that of austenitic stainless steel 321. The mechanical properties of the free cutting austenitic stainless steel are similar to those of 321 although the former are slightly lower than those of the latter.
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Zhang, Jiao, Qing Dong, Yong Bing Dai, Bao De Sun, and Hong Lan Xie. "Study of Fragment Behavior during Columnar-Equiaxed Transition of Hypoeutectic Alloy with Synchrotron Radiation." Materials Science Forum 706-709 (January 2012): 1743–48. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1743.
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In the present work, solidification of hypoeutectic, eutectic and hypereutectic Al-Cu alloys was illustrated by synchrotron X ray imaging, and the CET of hypoeutectic alloy was picked out to thorough investigated. The mechanism of hypoeutectic dendrites fragment behaviors among the nucleation area was studied by in-situ imaging and first-principles computation. The results show that the density difference between the fragments and the enriched melt leads to the movement of the fragments. The ejected fragments contributed to the columnar-eutectic transition and expanded the breadth of mush zone in front of the solid/liquid interface.
8
Sak-Saracino, Emilia, and Herbert M. Urbassek. "The α↔γ transformation of an Fe1−xCrx alloy: A molecular-dynamics approach." International Journal of Modern Physics C 27, no. 10 (August 29, 2016): 1650124. http://dx.doi.org/10.1142/s0129183116501242.
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Using molecular dynamics (MD) simulation, we study the temperature-induced [Formula: see text] phase transformation of an Fe[Formula: see text]Cr[Formula: see text] alloy. We find that the austenitic transition temperature is increased with respect to that of an Fe[Formula: see text]Ni[Formula: see text] alloy containing the same concentration of impurity atoms. During the austenitic transformation, heterogeneous nucleation of close-packed (cp) nuclei leads to a polycrystalline structure. The microstructure formed closely resembles that found in pure Fe and in FeNi alloys.
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HACIOGLU, TUGCE, AYSEN TEZCANER, SHERIF ABBAS, and ZAFER EVIS. "PREPARATION AND CHARACTERISTICS OF CO-DOPED HYDROXYAPATITE BIOMIMETIC COATINGS ON PRETREATED Ti6Al4V ALLOY." Surface Review and Letters 27, no. 11 (August 22, 2020): 2050012. http://dx.doi.org/10.1142/s0218625x20500122.
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In this study, [Formula: see text] co-doped and pure hydroxyapatites (HAp) were coated on rough surfaces of Ti6Al4V plates by biomimetic method. Prepared samples were investigated with SEM, EDS, FTIR, XRD and ICP. Furthermore, mechanical scratch tests, profilometer tests and in vitro cell studies were carried out. In order to explore the antibacterial characteristics of the coating, the survival rate of a bacteria named Staphylococcus epidermidis was determined. Structural investigations showed that HAp nucleation began four days after the immersion, expectedly nucleation developed collaterally with the incubation period and co-dopants had considerable effect on surface characteristics. Besides, the pretreatment procedure and dopants had notable impact on mechanical qualifications of the coatings. The critical load values obtained for coating failure were detected above 100[Formula: see text]mN in all types of coatings (max. critical load was obtained from 0.3[Formula: see text]mM co-doped coatings). Cancerous bone cells (SaOS-2) on prepared coatings were evaluated in terms of biological properties. 0.1-C7 and 0.3-C7 exhibited highest reduction percentage among all co-doped samples. Further increase in dopants concentrations up to 0.5[Formula: see text]mM lead to increase in toxicity and decrease in cell proliferation. Antibacterial test results showed the most antibacterial samples were 0.1-C7 and 0.3-C7, the results conformed with cell culture findings.
10
Michal, G. M., T. K. Glasgow, and T. J. Moore. "Spherulite Structures in a Melt Spun Fe-Ni Austenitic Steel." Proceedings, annual meeting, Electron Microscopy Society of America 43 (August 1985): 52–53. http://dx.doi.org/10.1017/s0424820100117339.
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Large additions of B to Fe-Ni alloys can lead to the formation of an amorphous structure, if the alloy is rapidly cooled from the liquid state to room temperature. Isothermal aging of such structures at elevated temperatures causes crystallization to occur. Commonly such crystallization pro ceeds by the nucleation and growth of spherulites which are spherical crystalline bodies of radiating crystal fibers. Spherulite features were found in the present study in a rapidly solidified alloy that was fully crysstalline as-cast. This alloy was part of a program to develop an austenitic steel for elevated temperature applications by strengthening it with TiB2. The alloy contained a relatively large percentage of B, not to induce an amorphous structure, but only as a consequence of trying to obtain a large volume fracture of TiB2 in the completely processed alloy. The observation of spherulitic features in this alloy is described herein. Utilization of the large range of useful magnifications obtainable in a modern TEM, when a suitably thinned foil is available, was a key element in this analysis.
11
Zhang, Weipeng, Bingge Zhao, Changdong Zou, Qijie Zhai, Yulai Gao, and Steve F. A. Acquah. "Investigating the Formation Process of Sn-Based Lead-Free Nanoparticles with a Chemical Reduction Method." Journal of Nanomaterials 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/193725.
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Nanoparticles of a promising lead-free solder alloy (Sn3.5Ag (wt.%, SnAg) and Sn3.0Ag0.5Cu (wt.%, SAC)) were synthesized through a chemical reduction method by using anhydrous ethanol and 1,10-phenanthroline as the solvent and surfactant, respectively. To illustrate the formation process of Sn-Ag alloy based nanoparticles during the reaction, X-ray diffraction (XRD) was used to investigate the phases of the samples in relation to the reaction time. Different nucleation and growth mechanisms were compared on the formation process of the synthesized nanoparticles. The XRD results revealed different reaction process compared with other researchers. There were many contributing factors to the difference in the examples found in the literature, with the main focus on the formation mechanism of crystal nuclei, the solubility and ionizability of metal salts in the solvent, the solid solubility of Cu in Ag nuclei, and the role of surfactant on the growth process. This study will help define the parameters necessary for the control of both the composition and size of the nanoparticles.
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Son, Junhyuk, Dong-Yurl Yu, Min-Su Kim, Yong-Ho Ko, Dong-Jin Byun, and Junghwan Bang. "Nucleation and Morphology of Cu6Sn5 Intermetallic at the Interface between Molten Sn-0.7Cu-0.2Cr Solder and Cu Substrate." Metals 11, no. 2 (January 25, 2021): 210. http://dx.doi.org/10.3390/met11020210.
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The nucleation kinetics and morphology of Cu6Sn5 IMCs at the interface between a Sn-0.7Cu-0.2Cr solder and Cu substrate were investigated in this study. A Sn-0.7Cu solder was utilized as a reference to elucidate the impact of Cr addition. The mechanical properties of the solder joints were determined via ball-shear tests. Cu coupons were dipped in the molten solders for 1 and 3 s at 240–300 °C, and the morphological analyses were conducted via electron microscopy. Both the solders contained scallop-like Cu6Sn5 IMCs. The smallest Cu6Sn5 IMCs were observed at 260 °C in both the solders, and the particle size increased at 280 and 300 °C. The IMCs in the Sn-0.7Cu-0.2Cr solder were smaller and thinner than those in the Sn-0.7Cu solder at all the reaction temperatures. The thickness of the IMCs increased as the reaction temperature increased. Inverse C-type nucleation curves were obtained, and the maximum nucleation rate was observed at an intermediate temperature. The shear strengths of the Sn-0.7Cu-0.2Cr solder joints were higher than those of the Sn-0.7Cu solder joints. This study will facilitate the application of lead-free solders, such as Sn-0.7Cu-0.2Cr, in automotive electrical components.
13
Duan, Rui Chun, and Hui Ji Shi. "A Study on the Corrosion Fatigue Characteristics of Al 2024-T3 Alloy." Key Engineering Materials 261-263 (April 2004): 1343–48. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.1343.
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In order to investigate how the corrosion dramatically reduces fatigue resistance of a 2024-T3 aluminium alloy, a series of corrosion experiments in a 3.5 wt% NaCl solution with different steeping time, and subsequent fatigue experiments under uniaxial cyclic load have been performed with the laminate specimens. The nucleation and growth of corrosion pits are found to occur mainly at the grain boundary. The optical micrographs of the experiments show that the fatigue micro-crack initiates on the bottom of the pit, expands its way through the neighbouring pits that located at the slip direction and then forms a main fatigue crack that leads to fracture. The similar corrosion experiments are also performed at different solution temperatures: 22 °C, 40°C, 60°C, and 80°C respectively. The effects of the steeping time and solution temperature on the fatigue life are investigated.
14
SPOWAGE, A. C., C. M. THONG, P. A. COLLIER, and G. Y. LI. "EFFECT OF SURFACE FINISHES ON THE THICKNESS AND MORPHOLOGY OF THE INTERMETALLIC LAYER IN LEAD-FREE SOLDER JOINTS." International Journal of Nanoscience 03, no. 06 (December 2004): 803–13. http://dx.doi.org/10.1142/s0219581x04002607.
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One of the most pressing challenges facing today's electronics packaging industry is to identify reliable and cost-effective solder alloys to replace toxic lead containing solder. Besides evaluating new alloy compositions and improving the soldering process, it is important to understand how surface finishes applied to the copper metallization affect the joint characteristics. The characterization of intermetallics during the early stages of nucleation and the growth is hindered by the nanoscopic grain size and layer thickness. This study investigates the impact of PCB finish and solder type on the interfacial intermetallics. Five types of solder and four types of finishes were used: Sn37Pb (SP), Sn3.5Ag (SA), Sn3.5Ag0.7Cu (SAC), Sn2Ag0.5Cu4Bi (SACB) and Sn3Bi8Zn (SBZ) solders, combined with immersion Silver ( I – Ag ), electroless Nickel-immersion Gold (ENIG), Organic Solderability Preservative (OSP) and immersion Tin ( I – Sn ). It was shown that both the SP and SAC solders follow a parabolic growth model and that the surface finish has a significant effect on the intermetallic morphology and growth kinetics. A combined SEM and XRD investigation was shown to be a suitable method for characterizing nanoscale intermetallics.
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Miura-Fujiwara, Eri, Yuya Ogawa, Mitsuo Niinomi, and Tohru Yamasaki. "Effect of Nb addition on high-temperature oxidation behavior, oxide layer structure, and its exfoliation resistance of Ti-Nb Alloys." MATEC Web of Conferences 321 (2020): 05018. http://dx.doi.org/10.1051/matecconf/202032105018.
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The authors proposed an oxide coating on Ti alloys for the dental abutment tooth, and they had reported that Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy forms a dense oxide layer by high-temperature oxidation. On the other hand, CP Ti forms a multilayered oxide consisted of rutile monolayers and the void layer. This morphological change by alloying is supposed to be mainly caused by Nb addition in Ti since the dense oxide layer of TNTZ mainly consists of rutile TiO2 and TiNb2O7. Therefore, in this study, oxidation behaviors of various range of Nb content of Ti-xNb alloys (x = 1 ~ 32 mol%) were investigated, and exfoliation resistance was evaluated. And in this paper, the oxide/metal interfacial microstructure of oxidized CP Ti, TNTZ alloy, and Ti-Nb alloy was studied by a transmission electron microscopy (TEM) and by a scanning transmission electron microscopy with an electron dispersive spectroscopy (STEM-EDS). The cross-sectional observations suggested that the substrate was gradually oxidized during heat treatment, and nucleation and grain growth of TiO2 and TiNb2O7 proceed at the metal/oxide interface. Consequently, the gradual oxidation process in TNTZ and Ti-Nb alloys could lead to its continuous interfacial microstructure and dense oxide structure, which can achieve high exfoliation resistance.
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Wang, Sheng Yu, and Anthony D. Rollett. "Abnormal Subgrain Growth by Monte Carlo Simulation Based on Hot-Rolled AA5005 Aluminum Alloy Texture." Materials Science Forum 558-559 (October 2007): 377–82. http://dx.doi.org/10.4028/www.scientific.net/msf.558-559.377.
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The subgrain structure of hot rolled aluminum alloy AA 5005 has been characterized on as-received samples using Electron Backscatter Diffraction (EBSD). Based on the OIM scans of RD-ND and TD-ND, 3 dimensional microstructures of subgrains are built up using the 3D Microstructure Builder, which is a method for developing statistically representative digital representations of microstructures. Following the generation of microstructure, different textures were fit to these reconstructed 3D microstructures, based on individual components such as Brass and S textures. For this study, the Brass texture was chosen as an exemplary case. Monte Carlo simulation was used to model subgrain coarsening and visualization was a key to detecting abnormal grain growth. The main objective is to understand the circumstances under which we can expect abnormal (sub-)grain growth to lead to nucleation of recrystallization.
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Chen, Chen, Xiao Dong Jia, Hang Zhang, Ran Wei, and Fu Shan Li. "A Centimeter-Size High Toughness Zr-Cu-Al-Nb Bulk Metallic Glass with Nano-Crystallization and Phase Separation." Materials Science Forum 913 (February 2018): 668–73. http://dx.doi.org/10.4028/www.scientific.net/msf.913.668.
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In this paper, a centimeter-size Zr-Cu-Al-Nb bulk metallic glass (BMG) with high notch toughness of 107±13 MPa∙m0.5 was designed and fabricated by copper mold casting. With 1% Nb substitution for Zr in Zr48Cu45Al7 glass forming alloy, the glass forming ability (GFA) and toughness of the BMG were enhanced significantly. The coexistence of nano-crystallization and phase separation in the glassy matrix was observed in Zr47Cu45Al7Nb1, which would possibly lead to the high toughness of this alloy due to the easy and populous nucleation of shear bands and the increasing resistance of shear band propagation. The influences of nano-crystallization and phase separation on the toughness of BMGs are discussed in detail. The strategy utilized in this study provides a novel approach in search for new BMGs with high toughness and good GFA.
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Lima Filho, Antonio de Pádua, Bruno Katsuyoshi Silama Ueda, Tales Paschoalino de Castro, and Rodrigo Alessandro Nunes de Oliveira. "Manufacture of Continuous Metal Matrix Composite Strip Reinforced by Particulate Materials from the Semisolid Processing." Solid State Phenomena 285 (January 2019): 189–96. http://dx.doi.org/10.4028/www.scientific.net/ssp.285.189.
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Strip casting is a new method of producing metal matrix composites. Two-roll melt dragged processing (TRMD-ing) and single-roll melt dragged processing (SRMD-ing) methods were used to study the manufacture of 2-mm-thick composite strips by using PbSn (≈ 11.3 g/cm3) eutectic alloy matrix reinforced with iron (≈ 7.86 g/cm3) powder (≈ 70 μm) at a rate of 0.3 m/s. The metallic powder stored in the feed hopper (≈ 90 g) was pushed during the pouring operation of the cast alloy (≈ 4 kg) at 260 oC on the cooling slope to produce a mixture of metallic slurry and particles to feed the nozzle to be dragged by the lower roll. Various surface defects occurred during processing, such as the failure of the powder particle to be embedded in the matrix by SRMD-ing with and without stirrer into the nozzle, and the rolling up of the strip into the nozzle by TRMD-ing. Graphite nanoparticles formed inside the α-Pb grain revealed a complicate eutectic structure in both the processing methods. The colloidal graphite used to coat the crucible, cooling slope, and nozzle could act as a nucleation agent for preferential centre segregation in the α-Pb grain. This suggests that the graphite nanoparticles functioned as nucleation points in the lead-rich α phase. Thus, another type of composite was formed in the presence of graphite nanoparticles within the lead-rich α-phase surrounded by β-Sn. An electron probe microanalysis and scanning electronic microscopy were used to investigate the composition and distribution and identify the different phases. Several types of particulate reinforcements may be added to the matrix to obtain composites for mechanical, electronic, and magnetic applications using these technologies.
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Mandal, Sumantra, A. K. Bhaduri, Baldev Raj, and V. Subramanya Sarma. "Dynamic Recrystallisation during Isothermal Hot Deformation in a Titanium Modified Austenitic Stainless Steel." Materials Science Forum 715-716 (April 2012): 140–45. http://dx.doi.org/10.4028/www.scientific.net/msf.715-716.140.
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The paper discusses the microstructural evolution during dynamic recrystallisation (DRX) of a titanium-modified austenitic stainless steel (alloy D9). Isothermal hot compression tests were conducted in a Gleeble thermo-mechanical simulator in the temperature range 1173-1373K to various strains at a constant strain rate of 0.1 and 1 s-1. The extent of DRX increased with increase in strain and temperature. Nucleation of new DRX grains was found to occur by bulging of parent grain boundary. A continuous sub-grain rotation around the original grain boundaries, which would lead to the formation of DRX nucleus in sub-grain structures, could not be confirmed from the present study. Fractions of Σ3 boundaries increased almost linearly with increase in area fraction of DRX. The generation of this Σ3 boundary was accounted for in the formation of annealing twins during DRX. The possible role of annealing twins on DRX in alloy D9 is also discussed.
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HE, DONG, JING CHUAN ZHU, YANG WANG, and YONG LIU. "A STUDY OF DYNAMIC RECRYSTALLIZATION IN TA15 TITANIUM ALLOY DURING HOT DEFORMATION BY CELLULAR AUTOMATA MODEL." International Journal of Modern Physics B 23, no. 06n07 (March 20, 2009): 934–39. http://dx.doi.org/10.1142/s0217979209060269.
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The dynamic recrystallization (DRX) of TA 15 ( Ti -6 Al -2 Zr -1 Mo -1 V ) titanium alloy during the hot deformation process was studied by the Cellular Automata (CA) model which is base on the dislocation density theory. To build the CA model, the dislocation density model, dynamic recovery model, nucleation model and grain growth model were introduced and developed. The influences of strain rate on the microstructure evolution and flow stress character were investigated which shows that high strain rate leads to later DRX appearance, high flow stress peak value, small mean size of recrystallizing grains( R -grains) and low DRX percentage, but they have the similar Avrami curve. The characteristic of DRX process in a modeling non-uniform temperature filed (NTF) has been studied. All the simulation results show good agreement with the pioneer's work and experimental results.
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Zhang, Mingquan, Jinghuai Zhang, Ruizhi Wu, Hongwei Cui, Ertuan Zhao, Shujuan Liu, Pengfei Qin, and Qing Ji. "The Effect of Y/Er and Zn Addition on the Microstructure and Mechanical Properties of Mg-11Li Alloy." Materials 12, no. 19 (September 20, 2019): 3066. http://dx.doi.org/10.3390/ma12193066.
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Although body-centered cubic (BCC) structural magnesium–lithium (Mg-Li) alloys have lower density and better formability than common hexagonal close-packed (HCP) Mg alloys, their applications remain limited due to their low strength. The purpose of this study is to investigate the effect of Y/Er and Zn addition on the microstructure and tensile properties of Mg-11Li alloy with a BCC structural matrix by comparing Mg-11Li, Mg-11Li-4Y-2Er-2Zn, and Mg-11Li-8Y-4Er-4Zn (wt %) alloys. The results indicate that the addition of Y/Er and Zn at a ratio of 3:1 cannot promote the formation of long-period stacking ordered structure in Mg-11Li alloy such as that in Mg-Y-Er-Zn alloys and the dominant intermetallic phases formed are BCC Mg24RE5 and face-centered cubic (FCC) Mg3RE2Zn3 phases. With an increase of the content of Y/Er and Zn in an as-cast alloy, the fraction of intermetallic particles increases and the grain size decreases. The addition of Y/Er, as well as Zn, dramatically promotes the refinement of dynamic recrystallization (DRX) during extrusion. The initial intermetallic phases induced by Y/Er and Zn addition are broken into relatively fine particles during extrusion, and this contributes to refining the dynamic recrystallized (DRXed) grains mainly by the particle stimulated nucleation mechanism. The as-extruded Mg-11Li-4Y-2Er-2Zn and Mg-11Li-8Y-4Er-4Zn alloys exhibit much higher tensile strength as compared with as-extruded Mg-11Li alloy, which is mainly ascribed to the refined DRXed grains and numerous dispersed intermetallic phase particles. It is suggested that further refinement of intermetallic particles in these extruded Mg-11Li-based alloys may lead to higher quality alloy materials with low density and excellent mechanical properties.
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Zhang, Xue Chao, Jing Wei Cheng, Bing Zheng, Xiu Chen Zhao, Ying Liu, and Ping Chen. "Nickel Nanoparticles Mediated Growth of the Intermetallic Compound between Sn-1.0Ag-Xni Solders Alloy and Cu Substrate." Materials Science Forum 815 (March 2015): 103–8. http://dx.doi.org/10.4028/www.scientific.net/msf.815.103.
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In the present study, the effect of addition of Ni nanoparticles on the growth of the intermetallic compound (IMC) layer between low-silver lead-free solder and Cu substrate was investigated. Ni nanoparticles were synthesized and smelted with pure Sn, Ag to prepare Sn-1.0Ag-xNi (x=0, 0.05, 0.1, 0.2) solder alloy. Sn-1.0Ag-xNi was soldered on a copper substrate, and then the solder/Cu couples were isothermally aged at 423K for 360h.The Cross-section images of IMCs layer were obtained to observe the morphology of IMC and to measure the thickness of Cu6Sn5and Cu3Sn layers respectively. The results show that, during aging, addition of Ni can remarkably improve the morphology of IMC, level the scalloped IMC, facilitate the growth of the total interfacial IMCs and inhibit the growth of Cu3Sn. Moreover, the rate change of thickness of the Cu3Sn reduced obviously with the increase of Ni nanoparticles. Comprehensive analysis shows that the addition of Ni promotes the nucleation and growth of Cu6Sn5. The thermodynamics calculation on the solder alloy was identical with the experiment result.
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Dehnavi, Mehdi, and Mohsen Haddad Sabzevar. "Grain size control in al-4.8 wt.% Cu alloy by computeraided cooling curve analysis." Metallurgical and Materials Engineering 20, no. 3 (September 30, 2014): 183–90. http://dx.doi.org/10.5937/metmateng1403183d.
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Generally Al–Ti and Al–Ti–B master alloys are added to the aluminium alloys for grain refinement. The cooling curve analysis (CCA) has been used extensively in metal casting industry to predict microstructure constituents, grain refinement and to calculate the latent heat of solidification. The aim of this study was to investigate the effect of grain refinement on the grain size of Al-4.8 wt.%Cu alloy by cooling curve analysis. To do this, alloy was grain refined by different amount of Al-5Ti-1B master alloy and all samples were solidified at constant cooling rate of 0.19 ℃/s. The temperature of the samples was recorded using a K thermocouple and a data acquisition system connected to a PC. The results show that the segregating power of Ti is very high and it segregates to the nucleant–liquid interface which leads to constitutional supercooling within which other nucleant particles get activated for nucleation. Other results show that with considering the changes in the primary undercooling (ΔTRU) as the main factor to determine the effectiveness of grain refinement process, it was found that by grain refinement, the value of undercooling decrease was approximately zero.
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Li, Lei, Yuantong Bi, Chunyan Ban, Haitao Zhang, Tie Liu, Xiangjie Wang, Claude Esling, and Jianzhong Cui. "A Crystallographic Study on the Growth of Partially Faceted MnSn2 Phase during Solidification Process." Crystals 8, no. 10 (September 29, 2018): 380. http://dx.doi.org/10.3390/cryst8100380.
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The growth of MnSn2 phase during the solidification process of Sn-Mn alloy was crystallographically investigated. The results show that the non-faced spherical caps of the MnSn2 crystals follow the continuous growth mechanism to grow rapidly along the <001> direction, while the side surfaces the two-dimensional nucleation mechanism to form the low index {100} and {110} facets. An interface structure analysis indicates that the atom planes within the {100} interplanar spacing period (IPSP) has a lower average reticular density than those within the {011} IPSP. This leads to the faster growth rates and thus the shortening and disappearance of the {100} side facets. As a consequence, the partially faceted (i.e., non-faceted spherical caps and faceted side surfaces) MnSn2 crystals follow an octagonal-base/spherical-cap geometric model (few crystals possess square bases) in three dimensions.
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Reali, Luca, Saïd El Chamaa, Daniel S. Balint, Catrin M. Davies, and Mark R. Wenman. "Deformation and fracture of zirconium hydrides during the plastic straining of Zr-4." MRS Advances 5, no. 11 (2020): 559–67. http://dx.doi.org/10.1557/adv.2020.145.
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ABSTRACTCrack initiation in zirconium alloys is an important issue for the safety of water-cooled fission reactors. Zirconium hydrides that precipitate in service are potential crack nucleation sites. In this work, the deformation and cracking of zirconium hydrides was studied during room temperature deformation of a Zircaloy-4 tensile sample up to fracture. The sample contained a hydrogen concentration of 100 ± 20 ppm. The main aims of this study were to better understand the mechanisms behind the hydride fracture in a polycrystalline matrix, and to identify at which point in the deformation of the Zr matrix the first hydrides break. Cracks thus nucleated may coalesce and propagate through the hydrided Zr-alloy. Scanning electron microscopy (SEM) images of a number of hydrides, both intergranular and intragranular, were taken at discrete increments of deformation during an interrupted tensile test. The results show that cracks in hydrides tend to always occur normal to the applied load, signalling the importance of the external stress. However, evidence is also provided to support the hypothesis that internal stresses generated by microstructural constraints may lead to the fracture of some intergranular hydrides.
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Kashin, Oleg, Konstantin Krukovskii, Aleksandr Lotkov, and Victor Grishkov. "Effect of True Strains in Isothermal abc Pressing on Mechanical Properties of Ti49.8Ni50.2 Alloy." Metals 10, no. 10 (September 30, 2020): 1313. http://dx.doi.org/10.3390/met10101313.
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The paper analyzes the microstructure and mechanical properties of Ti49.8Ni50.2 alloy (at.%) under uniaxial tension at room temperature after isothermal abc pressing to true strains e = 0.29 − 8.44 at T = 723 K. The analysis shows that as the true strain e is increased, the grain–subgrain structure of the alloy is gradually refined. This leads to an increase in its yield stress σy and strain hardening coefficient θ = dσ/dε at linear stage III of its tensile stress–strain curve according to the Hall–Petch relation. However, the ultimate tensile strength remains invariant to such refinement. The possible mechanism is proposed to explain why the ultimate tensile strength can remain invariant to the average grains size (dav). It is assumed that the sharp increase of the ultimate tensile strength σUTS begins when (dav) is less than the critical average grain size (dav)cr. In our opinion, for the investigated alloy (dav)cr ≈ 0.5 µm. In our study, the attained average grain size is larger the critical one. The main idea of the mechanism is next. In alloys with an average grain size (dav) less than the critical one, a higher external stress is required for the nucleation and propagation of the main crack.
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Herny, Emilie, Eric Andrieu, Jacques Lacaze, Frédéric Danoix, and Nicolas Lecoq. "Study by Differential Thermal Analysis of Reverse Spinodal Transformation in 15-5 PH Alloy." Solid State Phenomena 172-174 (June 2011): 338–43. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.338.
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Alloy 15-5 PH is a stainless steel with 15 wt.% Cr and 5 wt.% Ni that is precipitation hardened by addition of Cu. In its semi-finished state, this alloy consists in Cu-supersaturated soft martensite; its high specific properties come from a final tempering consisting in a heating to 550-600°C, holding for 4 hours, and then air cooling. This treatment leads to nanometric Cu precipitation that hardens the material and to transformation of some martensite to reverted austenite which is then stable and provides ductility. While a' embrittlement of such steels is known to occur at temperature in the range 450-520°C, it has been reported that they can be sensitive to the same phenomenon after long term ageing at temperature as low as 300°C, with a significant loss of ductility and an increase of the ductile-to-brittle transition temperature. Atom probe studies showed that this degradation is related to demixtion of martensite into Fe-rich and Cr-rich phases. Depending on the ageing temperature, demixtion can proceed through a nucleation and growth precipitation or by spinodal decomposition of the martensitic matrix. The present study reports differential thermal analyses (DTA) performed upon heating samples of material held at various temperatures (290-525°C) for various times (410 h to 8500 h) that have been characterized by atom probe. A clear DTA signal is obtained upon the reverse spinodal transformation that is further found to depend on ageing conditions.
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Zuiko, Ivan, Vladislav Kulitckii, and Rustam Kaibyshev. "Effect of Pre-Straining Method on Mechanical Properties of Thermo-Mechanically Processed Al-Cu-Mg Alloy." Defect and Diffusion Forum 385 (July 2018): 364–69. http://dx.doi.org/10.4028/www.scientific.net/ddf.385.364.
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The present study deals with the effect of pre-deformation technique of AA2519 alloy (Al–5.64Cu–0.33Mn–0.23Mg–0.15Zr–0.11Ti–0.09V–0.08Fe–0.01Si (wt. %)) under T8 tempers, on condition that intermediate strains are equal. After undergoing T87 by pre-stretching and peak ageing the alloy demonstrates the yield stress, ultimate tensile strength and elongation to failure of 425.4±2.4 MPa, 475±2.4 MPa, 12.1±0.4%, respectively. The 7% pre-straining by rolling leads to-5% decrease in yield stress, practically the same ultimate tensile strength and-20% decrease in ductility. This effect can be ascribed to more homogeneous distribution of dislocations which act as heterogeneous nucleation sites for the θ′-phase precipitation. In addition to precipitates of the Al–Cu family (θ′′ and θ′), Ω-phase plates on {111}α habit plane was observed. The effect of pre-straining prior to ageing on the precipitation behavior and its relation with mechanical properties of the AA2519 is considered.
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Kang, Zhi Qiang, Xue Yang, Guo Hui Feng, and Lin Zhang. "Experimental Study on the Impact of Macrosegregation Formation of the Al-Bi Hypermonotectic Alloys." Key Engineering Materials 727 (January 2017): 106–10. http://dx.doi.org/10.4028/www.scientific.net/kem.727.106.
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The solidification experiments about macrosegregation formation of the Al-10%Bi hyper monotectic alloys under gravity conditions have been carried out. The results showed that the average diameter of the Bi-rich droplets linearly increases and the number density of the Bi-rich droplets exponentially decreases with solidification time under the gravity condition. Because of gravity settling and collisions coagulation between the droplets, area fraction of Bi-rich increased rapidly in the bottom of samples during early solidification. It’s easy to form Bi-rich layer at the bottom of the sample. The analysis demonstrates that nucleation and diffusion growth of drops are the dominant factors influencing the solidification microstructure during the early solidification and the same distribution of Bi-rich in different locations of sample. As the solidification process, gravity migration and collision coagulation beginning to play the leading role, lead to the difference in the distribution of Bi-rich droplets in different locations of sample 90%e5%a2%9e%e5%a4%a7&tjType=sentence&style=&t=increases+gradually" increases gradually in the same time. It caused macrosegregation of the final solidification microstructure under the gravity condition.
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Fang, Shuang, Zhusheng Shi, Qian Bai, Jia Ying Jiang, Shu Yun Wang, and Jian Guo Lin. "An Investigation of Direct Powder Forging of Nickel Superalloy FGH96." Key Engineering Materials 716 (October 2016): 793–99. http://dx.doi.org/10.4028/www.scientific.net/kem.716.793.
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Powder metallurgy (PM) nickel-based superalloy has been widely used in high temperature applications and is most commonly manufactured using hot isostatic pressing (HIP). However, HIP is an expensive process and takes a long time at high temperature which leads to the formation of networks of prior particle boundaries (PPBs). In this study, a recently developed processing method - direct powder forging (DPF) was employed to produce a PM nickel-based superalloy component, using a single acting hydraulic press under normal atmosphere. EBSD study has been conducted for its microstructure, grains size distribution, and grain boundary misorientation; and mechanical testing has been carried out for its hardness and tensile properties at room temperature and 650°C. It has been found that the DPFed material has reached full density in the whole component. Networks of PPBs have been broken in the direct powder forged FGH96 alloy. Compared with HIPed FGH96 alloy, the DPFed material has a substantially higher recystallisation nucleation degree and more recrystallised sub-grains. After heat treatment, the tensile properties of the direct powder forged FGH96 alloy match or surpass those of the material produced by HIP plus isothermal forging.
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Mahmoud, M. G., A. M. Samuel, H. W. Doty, S. Valtierra, and F. H. Samuel. "Effect of Solidification Rate and Rare Earth Metal Addition on the Microstructural Characteristics and Porosity Formation in A356 Alloy." Advances in Materials Science and Engineering 2017 (2017): 1–19. http://dx.doi.org/10.1155/2017/5086418.
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The present study was performed on A356 alloy with the main aim of investigating the effects of La and Ce additions to 356 alloys (with and without 100 ppm Sr) on the microstructure and porosity formation in these alloys. Measured amounts of La, Ce, and Sr were added to the molten alloy. The results showed that, in the absence of Sr, addition of La and Ce leads to an increase in the nucleation temperature of the α-Al dendritic network with a decrease in the temperature of the eutectic Si precipitation, resulting in increasing the freezing range. Addition of 100 ppm Sr results in neutralizing these effects. The presence of La or Ce in the casting has a minor effect on eutectic Si modification, in spite of the observed depression in the eutectic temperature. It should be noted that Ce is more effective than La as an alternate modifying agent. According to the atomic radius ratio, rLa/rSi is 1.604 and rCe/rSi is 1.559, theoretically, which shows that Ce is relatively more effective than La. The present findings confirm that Sr is the most dominating modification agent. Interaction between rare earth (RE) metals and Sr would reduce the effectiveness of Sr. Although modification with Sr causes the formation of shrinkage porosity, it also reacts with RE-rich intermetallics, resulting in their fragmentation.
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Paul, H., A. Morawiec, T. Baudin, and T. Czeppe. "Tem Study of Recrystallization in Ultra-Fine Grain AA3104 Alloy Processed by High-Pressure Torsion." Archives of Metallurgy and Materials 60, no. 1 (April 1, 2015): 131–44. http://dx.doi.org/10.1515/amm-2015-0021.
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AbstractThe effect of annealing on the microstructure and the texture development was investigated in a particle containing AA3104 aluminium alloy. The samples were processed at room temperature by high-pressure torsion (HPT) up to ten turns. The nucleation of new grains was analyzed by a transmission electron microscope equipped with a system for local orientation measurements and a heating holder.The shear deformation induces a decrease of the grain size. After the first two turns of the HPT processing the initial structure of large grains was ‘transformed’ into a structure of fine cells/grains with the diameter of a few tens of nanometers. In the central areas of the samples the elongated shape of the cells/grains was observed up to six turns. For higher deformations, this structural inhomogeneity was totally removed and only the equiaxed grains were observed. The crystal lattice of small grains rotates in such a way that the <111> direction is parallel to the compression axis. After annealing the structure coarsened. Nevertheless, after primary recrystallization, the structure was still composed of relatively fine and equiaxed grains of a similar size. In most of the observed cases the size of the recrystallized grains in the areas close to and far from the large second phase particles was similar. The recrystallization leads to the creation of new texture components. The new grain orientations lost the positions typically observed in the deformed state and showed the tendency for the coincidence of the <100> crystallographic directions with the compression axis.
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Kaczorowski, M., P. Skoczylas, and A. Krzyńska. "Degradation of Creep Resistant Ni - Alloy During Aging at Elevated Temperature Part II: Structure Investigations." Archives of Foundry Engineering 15, no. 4 (December 1, 2015): 45–50. http://dx.doi.org/10.1515/afe-2015-0077.
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Abstract The results of structure observations of Ni base superalloy subjected to long-term influence of high pressure hydrogen atmosphere at 750K and 850K are presented. The structure investigation were carried out using conventional light-, scanning- (SEM) and transmission electron microscopy (TEM). The results presented here are supplementary to the mechanical studies given in part I of this investigations. The results of study concerning mechanical properties degradation and structure observations show that the differences in mechanical properties of alloy subjected different temperature are caused by more advanced processes of structure degradation during long-term aging at 850K, compare to that at 750K. Higher service temperature leads to formation of large precipitates of δ phase. The nucleation and growth of needle- and/or plate-like, relative large delta precipitates proceed probably at expense strengthening γʺ phases. Moreover, it can’t be excluded that the least stable γʺ phase is replaced with more stable γʹ precipitates. TEM observations have disclosed differences in dislocation structure of alloy aged at 750K and 850K. The dislocation observed in alloy subjected to 750K are were seldom observed only, while in that serviced at high stress and 850K dislocation array and dislocation cell structure was typical.
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Moulin, Gérard, Rania El Tahhan, Jérôme Favergeon, Michel Viennot, and Pascal Berger. "Interaction between Mechanical Loading in Creep and Reactivity of Zirconium and Zircaloy in Temperature." Materials Science Forum 522-523 (August 2006): 425–32. http://dx.doi.org/10.4028/www.scientific.net/msf.522-523.425.
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In order to study the nucleation and growth of cracks in the outer oxide scale which expand into the underlying alloy, deformation in creep in oxygen or in vacuum of zirconium and Zircaloy-4 has been studied mainly at 500°C. Influence of applied stresses, atmosphere and alloy’s grade on the deformation and oxidation processes are especially analyzed. The results underline the presence of two distinct deformation domains for both alloys grades, depending on the applied stress value. The presence of the oxide scale leads only to slight modifications on the deformation mechanism but it induces an increase of the deformation rate. This enhancement is especially observed in the case of the pre-oxidized Zircaloy-4 whose cracks remain mainly located in the outer part of the oxide. In opposite, the pre-oxidized zirconium shows cracks located down to the underlying metal. Acoustic emission is used to follow, in situ, in temperature the damage process of the outer zirconia layer during creep, and precisions about the oxidation mechanism and the effect of applied stress on oxygen diffusion and oxide growth rate are obtained thanks to the use of 18O as a marker.
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Zhang, Yan Ling, Xiao Gang Yang, Jin Gui Xu, and Li Guo Bai. "Effects of Alloying Elements on the Microstructure of 22CrMoH Gear Steels Billets." Advanced Materials Research 239-242 (May 2011): 3–14. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.3.
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In this study, the temperature field distribution of 22CrMoH billet is first obtained by simulating continuous casting process using moving boundary method. On the basis of the above data, the microstructure of 22CrMoH gear steels billet was simulated based on CAFÉ (Cellular Automaton – Finite Element Analysis) method, together with the effects of alloying elements such as Cr, Mo, Si, Mn on the microstructure of this billet. The simulated result agrees reasonably well with that of the actual product. And it suggested that under the reasonable extend of current steel grade, the increased amount of Si and Mn can steadily widen the proportion of equiaxed grains, lead to the increase in equiaxed grain amount, hence the decrease in equiaxed grain average radius; The increase in Mo content is able to enhance the nucleation amount; Proper decrease in Cr content favors the increase in proportion of equiaxed grains, but little effects on grain’s amount and radius. Further, the composition of alloy elements under the specified scope of 22CrMoH grade was optimized and the simulated results showed that the microstructure has vastly improved, as the proportion of equiaxed grain rose nearly doubled, the grains amount has increased by 19.96%, and average radius has decreased by 9.20%.
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Takamatsu, Yoshiko, Hisao Esaka, and Kei Shinozuka. "Formation of Primary Intermetallic Compounds in Sn-Ag-Cu Alloys." Materials Science Forum 654-656 (June 2010): 1397–99. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1397.
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Sn-Ag-Cu alloys are considered one of the most favorable lead-free solder systems. In slowly-cooled eutectic Sn-Ag-Cu alloys, sometimes large primary Ag3Sn or Cu6Sn5 intermetallic compounds (IMCs) form. These IMCs may affect the mechanical properties of solders. However, explanations for the formation of these IMCs are still not clear. This study deals with interrupted tests in order to clarify the nucleation of IMCs in the liquid phase. In this study, Sn-4.41Ag-0.63Cu and Sn-3.30Ag-1.47Cu alloys were prepared. According to the thermodynamic calculation, Pandat, the equilibrium solidification paths are described as follows: Sn-4.41Ag-0.63Cu :L → primary Ag3Sn → binary eutectic (Ag3Sn +Sn) → ternary eutectic; Sn-3.30Ag-1.47Cu :L → primary Cu6Sn5 → binary eutectic (Cu6Sn5 + Sn)→ ternary eutectic. The actual solidification process was different from the estimation from the equilibrium phase diagram. In the case of Sn-4.41Ag-0.63Cu, only Ag3Sn grew as a primary phase in the liquid, while in the case of Sn-3.30Ag-1.47Cu, not only primary Cu6Sn5 but also pseudo-primary Ag3Sn grew in the liquid. Ag3Sn may nucleate easily in the liquid phase, but Cu6Sn5 would not nucleate in the liquid.
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Souza, Fabrício Mendes, Ronald Lesley Plaut, Nelson Batista de Lima, Ricardo do Carmo Fernandes, and Angelo Fernando Padilha. "Recrystallization and crystallographic texture in AA4006 aluminum alloy sheets produced by twin roll caster and direct chill processes." Rem: Revista Escola de Minas 65, no. 3 (September 2012): 363–70. http://dx.doi.org/10.1590/s0370-44672012000300013.
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A recrystallization study of cold rolled metallic sheets is very important to evaluate the softening temperature for subsequent annealing. Crystallographic texture evolves during metal rolling and recrystallization. These processing steps can lead to an optimization of the grain orientation distribution in a metal strip and can improve, for instance, the stamping process, hence leading to a product with aggregated value. Softening curves were determined and compared for two sheets of the AA4006 aluminum alloy produced by the twin roll caster-TRC and by the direct chill-DC (under industrial process condition). It has been detected that the recrystallization of the strip produced by TRC process occurs at a higher temperature than the produced by DC process despite the little differences in their softening curves. The precipitation, in the TRC strip sample, occurs mainly before recrystallization and may occur during recrystallization. There is precipitation occurrence before and during recrystallization more expressive in the DC strip sample. Crystallographic texture of the sheet samples was obtained by X-ray diffraction and electron back scattering diffraction (EBSD) techniques. Results indicated the presence of a shear texture at the surface and β-fiber at the center of the cold rolled (70% area reduction) sample for the sheet produced by TRC process. In the strip sample obtained by the DC process, under the same conditions, the cube component and the β-fiber on the surface and at the center were observed. A random oriented grain texture has been detected in the two (TRC and DC) recrystallized (after cold rolling) sheet samples possibly due to the particle stimulated nucleation. The absence of β fiber in the recrystallized samples (TRC and DC) has also been observed.
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Khlybov, A. A., Yu G. Kabaldin, D. A. Ryabov, M. S. Anosov, and D. A. Shatagin. "Study of the damage to 12Cr18Ni10Ti steel samples under low cycle fatigue using methods of nondestructive control." Industrial laboratory. Diagnostics of materials 87, no. 5 (May 23, 2021): 61–67. http://dx.doi.org/10.26896/1028-6861-2021-87-5-61-67.
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The possibility of determining the degree of damage to flat samples in the area of low-cycle fatigue at the stage of accumulation of scattered damage before the appearance of a macroscopic crack is demonstrated. Flat samples were tested for cantilever bending at room temperature with a constant loading amplitude until a fatigue crack appeared. Austenitic steel 12Cr18Ni10Ti was used as a test material. The velocity (propagation time) of elastic waves in the material and the coercive force were measured upon testing at intervals of 500 cycles. The zone of damage development was analyzed and value of hardening (based on microhardness measurements) was determined within 15 mm of the developed crack. The analysis of the images of the alloy microstructures in the zone of the most likely crack propagation was performed following different number of cycles at the same point on the sample surface. The structural changes (γ – α transition (formation of martensite deformation)) that occur during cyclic loading, as well as nucleation and development of damage, followed by the formation of fatigue cracks, inevitably lead to changes in the elastic and magnetic properties of the material. At the initial stages of loading, we observed changes in the initial (both acoustic and magnetic) characteristics of the material, which later became stable or changed slightly. When operating time exceeded 80 % of the number of cycles before failure, a significant change in the measured parameters occurred. The obtained dependences of the acoustic and magnetic characteristics of the material provide reliable information about the current damage and can be used in estimating the residual life of the structures made of 12Cr18Ni10Ti steel.
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Andrade-Carozzo, V., and Pascal J. Jacques. "Interactions between Recrystallisation and Phase Transformations during Annealing of Cold Rolled Nb-Added TRIP-Aided Steels." Materials Science Forum 539-543 (March 2007): 4649–54. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4649.
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Fe and Fe-C based alloys present the exceptional feature that the processing route can be adapted to lead to various phases that present antagonist mechanical properties ranging from soft ferrite to high strength martensite. Among the different deformation mechanisms that can be exhibited by these phases, the TRIP effect brings about large enhancements of the work-hardening rate. The current TRIP-assisted multiphase steels present a ferrite-based matrix with a distribution of islands of bainite and retained austenite obtained at the end of specific thermal or thermomechanical treatments. The present study aims at characterising the interactions occurring between ferrite recrystallisation and austenite formation during the intercritical annealing of cold rolled Nb-added TRIP-aided steels. It is shown that the addition of niobium retards the ferrite recrystallisation during heating. As a consequence, ferrite may not be completely recrystallised before the nucleation and growth of the austenite grains. Strong interactions between these phenomena can then be observed, i.e. a strong hindering of the ferrite recrystallisation due to the austenite formation. Furthermore, the heating rate from room temperature to the intercritical temperature range influences the thermodynamic conditions prevailing at the ferrite / austenite interface and dictates the phase proportions.
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Grabke, H. J., M. Siegers, and V. K. Tolpygo. "Oxidation of Fe-Cr-Al and Fe-Cr-Al-Y Single Crystals." Zeitschrift für Naturforschung A 50, no. 2-3 (March 1, 1995): 217–27. http://dx.doi.org/10.1515/zna-1995-2-314.
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Abstract Single crystal samples of the alloy Fe-20%Cr-5%Al with and without Y-doping were used to study the "reactive element" (RE) effect, which causes improved oxidation behaviour and formation of a protective Al2O3 layer on this alloy. The oxidation was followed by AES at 10-7 mbar O2 up to about 1000 °C. Most observations were peculiar for this low pO2 environment, but yttrium clearly favors the formation of Al-oxide and stabilizes it also under these conditions, probably by favoring its nucleation. The oxides formed are surface compounds of about monolayer thickness, not clearly related to bulk oxides.Furthermore, the morphologies of oxide scales were investigated by SEM, after oxidation at 1000°C for 100 h at 133 mbar O2. On Fe-Cr-Al the scale is strongly convoluted and tends to spalling, whereas the presence of Y leads to flat scales which are well adherent. This difference is explained by a change in growth mechanism. The tendency for separation of oxide and metal was highest for the samples with low energy metal surface, i.e. (100) and (110), the scale was better adherent on the (111) oriented surface and on the polycrystalline specimen, since in the latter cases the overall energy for scale/metal separation is higher.All observations, from the low and from the high pO2 experiments, are discussed in relation to the approximately ten mechanisms proposed in the literature for explanation of the RE effects.
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Tillová, Eva, Mária Chalupová, Lenka Kuchariková, Juraj Belan, and Denisa Závodská. "Selection of optimal solution heat treatment of the casting cylinder heads." MATEC Web of Conferences 157 (2018): 02053. http://dx.doi.org/10.1051/matecconf/201815702053.
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The effect of solution treatment on mechanical properties (UTS, elongation, Brinell hardness) and microstructure (Si-morphology and Si-size) of an aluminium alloy (A356) used for casting cylinder heads was studied. The tests were carried out with specimens machined from the bulkheads of V8 engine blocks cast by the low pressure process. The samples were tested in as-cast and T6 heat treating conditions (solution heat treatment at 530°C with different time - 2, 3, 4, 5, 6, 7 hours, quenching in water at 20°C and precipitation hardened for 4 hour at 160°C). The results show that used heat treatment improves mechanical properties of the cylinder head casts. Tensile strength and hardness of specimens increase with solution treatment time. The hardness is a reflection of solution strengthening and silicon particle distribution in matrix. Solution temperature 530°C and 5 hours solution time is appropriate to obtain better morphology and distribution of Si particles in microstructure. Prolonged solution treatment (more than 5 hours) leads to a coarsening of the Si particles, while the numerical Si density decreases. As the particle density decreases, a fewer number of sites are available for crack nucleation, and hence, the fracture properties are improved. The data obtained from this study will be used to improve process control, and to help the selection of heat treatment of the casting for future products.
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Sheikha, Hussain, and Mehran Pooladi-Darvish. "The Effect of Pressure-Decline Rate and Pressure Gradient on the Behavior of Solution-Gas Drive in Heavy Oil." SPE Reservoir Evaluation & Engineering 12, no. 03 (May 31, 2009): 390–98. http://dx.doi.org/10.2118/109643-pa.
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Summary Heavy-oil recovery under solution-gas drive is affected by several interacting factors including pressure-decline rate and pressure gradients. It has been suggested that a high pressure decline rate (dp/dt) generates larger supersaturation and faster nucleation that leads to more-dispersed gas bubbles, while a high pressure gradient (?p) increases the viscous forces acting on the gas phase, enhancing bubble break up and gas dispersion. Both effects lead to lower gas mobility, affecting oil recovery; however, the relative importance of each is not known. Finding this is important to develop mathematical models and to allow extrapolation of experimental results to field conditions, where the relative importance of these factors changes with time and space. Previous experimental studies were affected by a combination of the two effects. In this paper, we distinguish between the effect of the pressure-decline rate and pressure gradient on gas mobility and oil recovery by varying these independently. In the experimental work reported in this paper, change in confining pressure is used to create a change in pressure-decline rate, and a change in production rate is used to change the pressure gradient. Several depletion experiments at varying pressure-decline rates and production rates are reported here. At a constant pressure-decline rate, the recovery factor tripled when the flow rate was increased by one order of magnitude. Similar experiments were conducted when the pressure-decline rate was increased by one order of magnitude but the flow rate was kept constant. In this case, the recovery factor did not change significantly. The results of this study clearly indicate that the pressure gradient has a much greater effect on gas mobility and oil recovery than pressure-decline rate has. This paper presents the experimental results and their analysis, along with the implications of these findings on modeling of solution-gas drive in heavy oils.
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Elibol, Cagatay, and Martin Wagner. "Virtual Extensometer Analysis of Martensite Band Nucleation, Growth, and Strain Softening in Pseudoelastic NiTi Subjected to Different Load Cases." Materials 11, no. 8 (August 17, 2018): 1458. http://dx.doi.org/10.3390/ma11081458.
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Pseudoelastic NiTi shape memory alloys exhibit different stress–strain curves and modes of deformation in tension vs. compression. We have recently shown that under a combination of compression and shear, heterogeneous deformation can occur. In the present study, we use digital image correlation to systematically analyze how characteristic features of the nominally uniaxial engineering stress–strain curves (particularly the martensite nucleation peak and the plateau length) are affected by extensometer parameters in tension, compression, and the novel load case of shear-compression. By post-experimental analysis of full surface strain field data, the effect of the placement of various virtual extensometers at different locations (with respect to the nucleation site of martensite bands or inhomogeneously deforming regions) and with different gauge lengths is documented. By positioning an extensometer directly on the region corresponding to the nucleating martensite band, we, for the first time, directly record the strain-softening nature of the material—a specific softening behavior that is, for instance, important for the modeling community. Our results show that the stress–strain curves, which are often used as a basis for constitutive modeling, are affected considerably by the choice of extensometer, particularly under tensile loading, that leads to a distinct mode of localized deformation/transformation. Under compression-shear loading, inhomogeneous deformation (without lateral growth of martensite bands) is observed. The effects of extensometer gauge length are thus less pronounced than in tension, yet systematic—they are rationalized by considering the relative impact of differently deforming regions.
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Yang, Hongyan, Xiaohong Zhan, Hengchang Bu, Wanping Ma, and Feiyun Wang. "Study on bubble morphology at interface of laser direct joint between carbon fiber reinforced thermoplastic (CFRTP) and titanium alloy." Journal of Polymer Engineering 40, no. 10 (November 26, 2020): 868–75. http://dx.doi.org/10.1515/polyeng-2020-0112.
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AbstractLaser direct joining of carbon fiber reinforced thermoplastic (CFRTP) composite plate and titanium alloy plate with a thickness of 2 mm was performed with swing laser. Numerous air bubble of submillimeter size were observed inside the fusion zone of CFRTP and titanium alloy at the cross section of the joints. The air bubble characteristics were analyzed based on the morphology and size, while the formation mechanism of air bubble was further elucidated according to the nucleation mode, nucleation site and nucleation position. The results demonstrated that the nucleation modes of air bubble are substantially divided into homogeneous nucleation and heterogeneous nucleation, which is related to the nucleation sites. The nucleation mode presents a crucial factor influencing the position and morphology of air bubble. In addition, the air bubble characteristics are also determined by the clamp pressure and resin flow. The final morphology of air bubble is primarily represented by four typical types.
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Hu, Hui E., Zhou Lu, Xiao Hong Su, and Jing Xin Deng. "Study of the crystallization kinetics of a Zr57Cu15.4Ni12.6Al10Nb5 amorphous alloy." International Journal of Materials Research 111, no. 10 (October 1, 2020): 849–56. http://dx.doi.org/10.1515/ijmr-2020-1111009.
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Abstract The non-isothermal crystallization kinetics with heating rates ranging from 10 K s-1to 80 K s-1and the isothermal crystallization kinetics during annealing from the glass transition temperature to the crystallization onset temperature of a Zr57Cu15.4Ni12.6Al10Nb5 amorphous alloy were studied in detail using X-ray diffraction and differential scanning calorimetry. During non-isothermal crystallization, it is more difficult to nucleate than to grow, and the crystallization resistance increases first and then decreases. During isothermal crystallization of the alloy from 713- 728 K, there are two exothermic peaks corresponding to a diffusion-controlled growth process with decreasing nucleation rate and increasing nucleation rate. From 733- 748 K, only one exothermic peak appears, and the growth process is controlled by the interface with decreasing nucleation rate. Isothermal crystallization is a process in which the crystallization resistance increases. The resistance of isothermal crystallization is less than that of non-isothermal crystallization.
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Zhang, Dongqiao, Yajun Yin, Jianxin Zhou, and Zhixin Tu. "Phase Field Study of Microstructure Evolution in Eutectoid Phase Transformation – I Nucleation." Archives of Foundry Engineering 17, no. 3 (September 1, 2017): 155–62. http://dx.doi.org/10.1515/afe-2017-0109.
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Abstract Eutectoid growth, as the important reaction mechanism of the carbon steel heat treatment, is the basis to control the microstructure and performance. At present, most studies have focused on lamellar growth, and did not consider the nucleation process. Mainly due to the nucleation theory is inconclusive, a lot of research can support their own theory in a certain range. Based on the existing nucleation theory, this paper proposes a cooperative nucleation model to simulate the nucleation process of eutectoid growth. In order to ensure that the nucleation process is more suitable to the theoretical results, different correction methods were used to amend the model respectively. The results of numerical simulation show that when the model is unmodified, the lateral growth of single phase is faster than that of longitudinal growth, so the morphology is oval. Then, the effects of diffusion correction, mobility correction and ledges nucleation mechanism correction on the morphology of nucleation and the nucleation rate were studied respectively. It was found that the introduction of boundary diffusion and the nucleation mechanism of the ledges could lead to a more realistic pearlite.
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Jiang, Xueqi, Xiaoqiang Shi, Xiaoguang Fan, and Qi Li. "Formation of Large Size Precipitate-Free Zones in β Annealing of the Near-β Ti-55531 Titanium Alloy." Metals 9, no. 5 (May 10, 2019): 544. http://dx.doi.org/10.3390/met9050544.
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Large size (>10000 μm2) precipitate-free zones in the absence of microsegregation were observed in the near-β Ti-55531 titanium alloy after furnace cooling from high temperature and longtime annealing in the single-β phase field. To reveal the formation mechanism of the large size precipitate-free zone, continuous cooling and isothermal heat treatment were carried out to investigate the β-α phase transformation process. It was found that the large size precipitate free zone is attributed to the heterogeneous nucleation of α phase. The nucleation site evolves in three different modes: I-random nucleation inside the β grain, II-network nucleation inside the β grain and, III-heterogeneous nucleation on the precipitated α phase. Modes I and II lead to homogeneous transformed structure while Mode III results in the large size precipitate-free zone. Both modes II and III are promoted at high annealing temperature, rapid cooling above 600 °C or slow cooling below 600 °C. Mode II is common as it can minimize the strain energy in phase transformation. As a result, the formation of the large size precipitate-free zone is not deterministic.
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Li, J. Q., J. L. Chen, Xianyi Li, and Xiao Li Ma. "Effects of Al-5Ti-B-2RE on the Microstructures and Mechanical Properties of Al-10Mg Alloy." Applied Mechanics and Materials 55-57 (May 2011): 828–31. http://dx.doi.org/10.4028/www.scientific.net/amm.55-57.828.
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This paper reported the effects of Al-5Ti-B-2RE on the microstructures and mechanical properties of an Al-10Mg alloys. It has been shown that the addition of 6wt.% Al-5Ti-B-2RE alloy can decrease the average grain sizes and increase the mechanical properties of the Al-10Mg alloy. Grain refinement mechanism is due to TiAl3andTiB2particles formation nucleation of aluminum，rare earth elements enhancing the kinetics of α-Al nucleation and inducing low growing speed of crystals. And the grain refinement strengthening and dispersion strengthening lead to improve the mechanical properties.
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Wang, Zheng, Mao Zhong An, Jie Yu, and Xu Ri Hu. "Study of Electroplating Zn-Sn-Ni Alloy." Materials Science Forum 575-578 (April 2008): 1338–42. http://dx.doi.org/10.4028/www.scientific.net/msf.575-578.1338.
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When Zn-Sn-Ni ternary alloy is electroplated on electrolyte copper foil, the surface properties can be comprehensively improved by using alkaline salt pyrophosphate solution. After the bath composition and processing conditions are optimized, and an appropriate additive is chosen, the SEM images shows the electrocrystalized substance obtained is composed of nano-crystals. Besides, XRD analysis on the deposits of electroplated Zn-Sn-Ni alloy shows Zn in the deposits exist in the form of metal compound, including δ phase Ni3Zn22 as well as γ Ni5Zn21. This indicates under the pyrophosphate salt the process of nucleation of Zn-Sn-Ni ternary alloy is similar to the process of three-dimensional successive nucleation controlled by diffuseness. All these demonstrate that after the disposal of this study, the corrosion resistance, the heat resistance and the binding intensity of electrolyte copper foil are obviously improved.
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Thompson, C. V. "On the role of diffusion in phase selection during reactions at interfaces." Journal of Materials Research 7, no. 2 (February 1992): 367–73. http://dx.doi.org/10.1557/jmr.1992.0367.
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It is argued that interdiffusion must precede nucleation of new phases during reactions at interfaces between compositionally different phases. The relative rates at which elemental components diffuse in the reacting phases control the sequence in which phases can form, and can also strongly affect the relative nucleation rates of alloy products, especially in the transient nucleation regime. While detailed predictions of the relative nucleation rates require usually unavailable knowledge of the energies of the relevant interfaces, in some cases, knowledge of the relevant diffusivities, along with a thermodynamic analysis, can lead to predictions of likely phase formation sequences. These concepts are used to explain the association of diffusional asymmetry with systems that undergo solid state amorphization, and to specify semiquantitatively the degree of asymmetry required for solid state amorphization.