Journal articles: 'Alloy grain structure'

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Chi, Xiang, Ying Li, De-quan Er, Xu-hao Han, Xiu-li Duan, Ji-bing Sun, and Chun-xiang Cui. "Study of Structure and Magnetic Properties of SmCo10 Alloy Prepared by Different Methods." Advances in Materials Science and Engineering 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/6457534.

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In this paper, the phase compositions, microstructures, atomic structures, and magnetic properties of Co-rich SmCo10 alloys prepared by arc-melting, annealing, and melt-spinning were studied. It was found that as-cast alloy is composed of Th2Zn17-type Sm2Co17 matrix with an average grain size of ∼45 μm accompanied by lamellar eutecticum (consisting of α-Co and Th2Zn17-type Sm2Co17) distributed at grain boundaries. The annealed alloy has the same phase composition and phase distribution as the as-cast alloy except that the average grain size decreases to ∼35 μm, and the eutecticum has more homogeneous distribution on the matrix. Simultaneously, the atomic structure of Sm2Co17 is unchanged with only a decrease in structural disorder after annealing. The as-spun ribbons are composed of ∼95.5 vol.% TbCu7-type Sm2Co17 and the rest α-Co. The short rod-shaped α-Co grains are intermittently distributed at the grain boundaries of equiaxed Sm2Co17 grains. The as-spun ribbons show a higher coercivity, and the annealed alloy shows maximum magnetization. The structural parameters were calculated by Extended X-ray Absorption Fine Structure (EXAFS), and the relationship between structure and magnetic properties was discussed in detail.

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Perevalova, O. B., N. A. Koneva, and É. V. Kozlov. "Grain structure of Ni3Fe alloy." Russian Physics Journal 42, no. 11 (November 1999): 952–59. http://dx.doi.org/10.1007/bf02509688.

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Yang, Zhenquan, Aibin Ma, Huan Liu, Jiapeng Sun, Dan Song, Ce Wang, Yuchun Yuan, and Jinghua Jiang. "Multimodal Microstructure and Mechanical Properties of AZ91 Mg Alloy Prepared by Equal Channel Angular Pressing plus Aging." Metals 8, no. 10 (September 26, 2018): 763. http://dx.doi.org/10.3390/met8100763.

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Developing cost-effective magnesium alloys with high strength and good ductility is a long-standing challenge for lightweight metals. Here we present a multimodal grain structured AZ91 Mg alloy with both high strength and good ductility, prepared through a combined processing route of low-pass ECAP with short-time aging. This multimodal grain structure consisted of coarse grains and fine grains modified by heterogeneous precipitates, which resulted from incomplete dynamic recrystallization. This novel microstructure manifested in both superior high strength (tensile strength of 360 MPa) and good ductility (elongation of 21.2%). The high strength was mainly attributed to the synergistic effect of grain refinement, back-stress strengthening, and precipitation strengthening. The favorable ductility, meanwhile, was ascribed to the grain refinement and multimodal grain structure. We believe that our microstructure control strategy could be applicable to magnesium alloys which exhibit obvious precipitation strengthening potential.

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Mackenzie, R. A. D., M. D. Vaudin, and S. L. Sass. "Grain boundary structure in Ni3Al." Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 602–3. http://dx.doi.org/10.1017/s0424820100105072.

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Ni3Al is a potentially useful high temperature alloy. In its single crystal form it exhibits good ductility, however in polycrystalline form the pure alloy is highly prone to intergranular failure. It has been seen that in slightly nickel-rich alloys the addition of small amounts of boron has the effect of dramatically increasing the material ductility and of changing the failure mode from intergranular to transgranular. In alloys which have been ductilitized by boron addition, atom probe investigation has shown the boron to be segregated to grain boundaries. This segregation may induce a change in the boundary structure as has been seen by Sickafus and Sass in gold doped iron bicrystals.Small angle boundaries in polycrystals and fabricated bicrystals have been examined using transmission electron microscopy. The bicrystals were produced by hot pressing misoriented single crystals of either pure or doped Ni3Al. Boundaries have been observed in a variety of fabricated bicrystals.

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Zhao, Da Zhi, Ke Hu, and Qi Chi Le. "The Influence of Un-DRXed Grains on Mechanical Properties of Mg-Zn-Mn-La-Ce Alloys." Key Engineering Materials 821 (September 2019): 237–43. http://dx.doi.org/10.4028/www.scientific.net/kem.821.237.

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The effect of extrusion temperature on the mechanical properties of low-Zn containing wrought Mg alloys manufactured by indirect extrusion was studied. The experiments were performed on Mg-Zn-Mn based alloy with addition of LaMM (La rich misch metal). The alloys presented typical bimodal grain structure consisted of large elongated un-DRXed grains and fine recrystallized grains when extruded at relatively low temperature. The alloy showed excellent balance of strength and elongation. The distinct grain structure generated in this study allowed the influence of un-DRXed grains on yield strength to be investigated.

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Li, Jian Ping, Li Bang Zeng, Da Heng Mao, and Hong Feng Jiang. "Experimental Research on Ultrasound Cast-Rolling Lead Alloy Strip." Advanced Materials Research 366 (October 2011): 181–86. http://dx.doi.org/10.4028/www.scientific.net/amr.366.181.

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With the ultrasound was put into the experiment of cast-rolling lead alloy strip, it broke the dendrite structures and enhanced the under-cooling by the effect of cavity and acoustic streaming. The microstructure comparison of ultrasound and general cast-rolling shows that: The grain size of general cast-rolled lead strip is big; the grain boundary is coarse and the organization structure is uneven. However, the grain structure is refined, smaller grains and uniform organization structure is acquired with ultrasound treatment. Besides, the mechanical properties test results of the two kinds lead alloys shows that the ultrasound cast-rolling lead alloys are better than general cast-rolling. The tensile strength, yield strength and elongation of ultrasound cast-rolling lead strip are increased by 11.30%, 22.15% and 21.74% than that of general cast-rolling lead strip.

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Pasang, Timotius, V. Satanin, M. Ramezani, M. Waseem, Thomas Neitzert, and O. Kamiya. "Formability of Magnesium Alloys AZ80 and ZE10." Key Engineering Materials 622-623 (September 2014): 284–91. http://dx.doi.org/10.4028/www.scientific.net/kem.622-623.284.

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Formability of two magnesium alloys, namely, AZ80 and ZE10, has been investigated. Both alloys were supplied with a thickness of 0.8 mm. The grain structure of the as-received AZ80 alloy showed dislocations, twins and second-phase particles and-/or precipitates distributed uniformly within grains. These were not obvious on the ZE10 alloy. The investigations were carried out at room temperature for both alloys in the as-received and heat treated conditions (410oC for 1 hour followed by water quench). The heat treatment significantly changed the grain structure of the AZ80 alloy, but did not affect the ZE10 alloy apart from grain enlargement. The formability was studied on the basis of plastic strain ratio (r) and strain hardening coefficient (n) by means of tensile testing. In the as-received condition, the ZE10 alloy had a slightly better formability () than AZ80 alloy. Following heat treatment, however, the formability of the AZ80 alloy was improved significantly (by about 26%), while the ZE10 alloy did not show any significant change.

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Tang, Haochun, Tso-Fu Mark Chang, Yaw-Wang Chai, Chun-Yi Chen, Takashi Nagoshi, Daisuke Yamane, Hiroyuki Ito, Katsuyuki Machida, Kazuya Masu, and Masato Sone. "Nanoscale Hierarchical Structure of Twins in Nanograins Embedded with Twins and the Strengthening Effect." Metals 9, no. 9 (September 6, 2019): 987. http://dx.doi.org/10.3390/met9090987.

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Hierarchical structures of 20 nm grains embedded with twins are realized in electrodeposited Au–Cu alloys. The electrodeposition method allows refinement of the average grain size to 20 nm order, and the alloying stabilizes the nanoscale grain structure. Au–Cu alloys are face-centered cubic (FCC) metals with low stacking fault energy that favors formation of growth twins. Due to the hierarchical structure, the Hall–Petch relationship is still observed when the crystalline size (average twin space) is refined to sub 10 nm region. The yield strength reaches 1.50 GPa in an electrodeposited Au–Cu alloy composed of 16.6 ± 1.1 nm grains and the average twin spacing at 4.7 nm.

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Son, Hyeon Taek, Jae Seol Lee, Young Kyun Kim, Ik Hyun Oh, Kyosuke Yoshimi, and Kouichi Maruyama. "Effects of Samarium on Microstructure and Mechanical Properties of Mg-Al-Ca Alloys." Materials Science Forum 544-545 (May 2007): 295–98. http://dx.doi.org/10.4028/www.scientific.net/msf.544-545.295.

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As samarium addition was increased, α- Mg matrix morphology was changed from dendritic to equiaxed grains and average value of grain size was decreased from 101.6㎛ to 39.3㎛. Samarium addition to Mg-5Al-3Ca based alloys resulted in the formation of Mg-Al-Sm thernary intermetallic compounds at grain boundarys and α-Mg matrix grains. In these alloys, two kinds of eutectic structure were observed; coarse irregular-shape structure at grain boundary and fine needle-shape structure in the α-Mg matrix grain. It is found that the yield strength and ultimate strength showed the maximum value of 109.1MPa and 139.3 at Mg-5Al-3Ca-2Sm alloy, respectively.

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Ko, Jun Yeong, and Sun Ig Hong. "Effect of Carbon Addition on the Cast and Rolled Microstructures of FeCoCrNiMn High Entropy Alloys." Key Engineering Materials 737 (June 2017): 16–20. http://dx.doi.org/10.4028/www.scientific.net/kem.737.16.

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In this study, the effect of carbon addition the cast and rolled microstructures of Cantor alloy type FeCoCrNiMn high entropy alloys. Both as-cast FeCoCrNiMn and FeCoCrNiMnC0.1 alloys have dendritic microstructure. Small particles, which may be associated carbon addition exist in the dendrite arms in FeCoCrNiMnC0.1 alloy. After homogenization treatment at 1327K for 24 hrs., dendritic structure was completely eliminated after annealing. Dendritic structure was converted to the structure with elongated grains, especially for carbon added FeCoCrNiMnC0.1. The development of elongated grains is associated with the direction of the primary arms in the dendritic structure. Carbides are segregated at the grain boundaries in FeCoCrNiMnC0.1 alloy. It also appears that growth of grains is impeded by the segregation of carbides. It is apparent that the grain boundary precipitates are Cr-rich. Both the strength and ductility of FeCoCrNiMnC0.1 increased over FeCoCrNiMn with the addition of 0.1 wt. % carbon. The increase of ductility in FeCoCrNiMnC0.1 may be caused by the rapid hardening in FeCoCrNiMnC0.1 due to dislocation-solute interaction.

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Liu, Shi Chao, Hang Chen, Jun Jia Zhang, Peng Fei Wang, Jin Chuan Jie, and Ting Ju Li. "Solidification Structure of 6063 Alloy under Pulsed Magnetic Field." Materials Science Forum 817 (April 2015): 355–59. http://dx.doi.org/10.4028/www.scientific.net/msf.817.355.

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The influences of pulsed magnetic field (PMF) on solidification structure of 6063 alloy were studied in this article. The results show that solidification structure of 6063 alloy can be refined with the application of PMF. The dendrite growth restrained and the macrostructure changed from large dendrite grains to fine equiaxed grains. The grain size decreased when the voltage increased from 0V to 600V. However, when the pulse frequency increased from 5Hz to 15Hz, the average grain size decreased continuously until reached a limit, and then the grains coarsened with further increase of the pulse frequency. The vibration caused by PMF not only made the temperature field of the melt uniform ,but also brook off the initial solidified grains formed on the cold wall of the mold, and spurs the grains to move to the center of melt which can be acted as nuclei.

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Ning, Jiang Li, Da Ming Jiang, Bing Yu Qian, Xi Gang Fan, Bao You Zhang, Jie Yu, and Xin Mei Zhang. "Microstructure and Thermal Stability of Al-Mg-Mn Alloys by Equal Channel Angular Pressing at Elevated Temperature." Materials Science Forum 546-549 (May 2007): 929–32. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.929.

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Two Al-Mg-Mn alloys having similar compositions but with and without Zr addition were subjected to equal channel angular pressing (ECAP) at 350°C using route BC and a 90° die, followed by water quenching or air cooling. A series of annealing experiments were conducted at various temperatures from 400°C to 460°C on the water-quenched alloys. Fine structures with grain size of approximately 1~2μm were obtained in these alloys after 6 passes. The water-quenched alloy containing Zr exhibited finer structure compared with the Zr-free alloy in the same cooling condition, which was due to the existence of Al3Zr dispersoids. And in the air cooling condition, it was found that in the Zr-free alloy static recovery occurred, and in partial regions some small grains without dislocation inside appeared suggesting the occurrence of static recrystallization. This demonstrated a fairly restored structure. However, the microstructure of the alloy containing Zr kept stable during the air cooling process. In addition, in the annealing experiments, secondary recrystallization took place in the Zr-free alloy annealed at 410°C for 1h, while the alloy containing Zr kept stable up to 460°C. TEM observation showed that the Al3Zr dispersoids pinned the motion of the grain boundaries, thereby the secondary recrystallization and grain growth were inhibited.

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Nie, Shuang, Bingyang Gao, Xuejian Wang, Zhiqiang Cao, Enyu Guo, and Tongmin Wang. "The Influence of Holding Time on the Microstructure Evolution of Mg–10Zn–6.8Gd–4Y Alloy during Semi-Solid Isothermal Heat Treatment." Metals 9, no. 4 (April 8, 2019): 420. http://dx.doi.org/10.3390/met9040420.

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A semi-solid microstructure of Mg–10Zn–6.8Gd–4Y alloys is acquired via an isothermal heat treatment process, and the effects of the holding time on the microstructure evolution of Mg–10Zn–6.8Gd–4Y alloys are investigated. The results show that the microstructure of the cast alloy is composed of primary α-Mg dendritic grains with a eutectic structure (W-phase and eutectic Mg) distributed at the grain boundaries. The primary α-Mg dendritic grains grow in size with increasing holding time, and they tend to grow into more globular structures in the initial stage; they then become a bit more dendritic, as small branches grow from the grain boundaries after holding the sample at 580 °C for 10 min. Meanwhile, the interdiffusion of magnesium atoms within the eutectic region, and between the primary α-Mg and eutectic structure, leads to the formation of fine and relatively globular eutectic Mg grains in the eutectic structure after holding for 10 min. The eutectic Mg grains begin to grow, coarsen, coalesce, or be swallowed by the surrounding primary grains, causing fluctuations of the general grain size. Over the whole isothermal heat treatment process, two mechanisms—coalescence and Ostwald ripening—dominate the grain coarsening.

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Sun, Lin, Ming-An Chen, and Yun-Lai Deng. "The effect of grain structure on the corrosion resistance of 7050 aluminum alloy." International Journal of Modern Physics B 33, no. 01n03 (January 30, 2019): 1940011. http://dx.doi.org/10.1142/s0217979219400113.

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Multi-direction isothermal forging of 7050 aluminum alloy at 103s1 strain rate and temperature of 3000C are observed. EBSD is used to characterize the grain structure, and the Vickers hardness and intergranular corrosion (IGC) properties are tested. The results of EBSD indicate that the sub-grains increase and the grain size decreases gradually as the pass of isothermal forging increases. The volume fraction of sub-grain has great effect on the corrosion resistance. The more sub-grains are included in the grain structure, the better the corrosion resistance and the mechanical properties. The grain size also influences the corrosion resistance, and the decreasing of the grain size is adverse to the corrosion resistance but is good for mechanical properties.

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Kodjamanova, P., H. Fietzek, Maria Juez-Lorenzo, Vladislav Kolarik, and Heike Hattendorf. "In Situ Study of Real Structure Effects on the Initial Oxidation of FeCrAl Alloys by Two-Dimensional High Temperature X-Ray Diffraction." Materials Science Forum 522-523 (August 2006): 69–76. http://dx.doi.org/10.4028/www.scientific.net/msf.522-523.69.

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In order to contribute to a better understanding of the processes, which occur in the structure of FeCrAl alloys during oxidation, in situ – studies by two-dimensional high temperature X-ray diffraction (2D-XRD) using a global area detector and grazing incidence with a monocapillary have been performed. The 2D-XRD yields simultaneously with the identification of the oxides and their formation kinetics information about the grain size, grain shape, stresses, texture as well as grain movements during the oxidation process of both oxide and metal. Two commercial FeCrAl alloys with different reactive element additions were investigated in the temperature range of 850°C to 1100°C. In the range of 1100°C already in the first 5 min the alloy grains become coarse and appear as single spots along the lateral profile in the 2D-XRD pattern. Dynamic displacement of these spots along the 2θ – axis during the exposure indicates the formation of stresses, which differ from grain to grain. Initially, re-crystallisation and grain growth dominate and grains disappear and new grains appear. On further exposure the grains twist continuously with 1° to 3° per hour, depending on the alloy. The “dancing grain” effect of the alloy is probably related with growth stresses in the oxide scale and influenced by the bulging of the foil. Simultaneously, α-Al2O3 is detected from the first pattern after 5 min and shows an enhanced formation rate in the first 15 min of the oxidation. The α-Al2O3 grains are with 0.3 to 0.4 4m extremely fine and, a dense well adherent scale is observed even after 1 h.

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Zuo, Xiu Rong, and Hai Chao Cui. "Effect of Minor Sc, Zr and Ti Additions on the Microstructures and the Mechanical Properties of Pure Aluminium." Advanced Materials Research 152-153 (October 2010): 1071–78. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.1071.

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Different alloys with the minor Sc, Zr and Ti additions were prepared. Microstructures and mechanical properties of the alloys were studied. The results show that the Al-0.25%Sc-0.2%Zr alloy has smaller grain than that of the Al-0.25%Sc alloy, grains of which change from the columnar structure to the fine equiaxed structure because of 0.2%Zr addition. The as-cast Al-0.25%Sc-0.2%Zr-0.03%Ti alloy has the finest grain and the highest hardness of all the studied as-cast alloys. This behavior can be attributed to the fine Al3Sc, Al3(Sc,Zr) and Al3(Sc,Ti) particles, which not only act as the ideal nuclei for α(Al) but also produce grain-size strengthening and dispersion strengthening. The strength of the Al-0.25%Sc-0.2%Zr alloy is not higher than that of the Al-0.25%Sc alloy after hot extrusion because of the presence of Al3(Sc,Zr) particles with smaller misfit with Al than Al3Sc, which brings the transition of dislocation moving mechanism from Orowan bypassing to shearing of the particles.

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Sizova, Olga, Galina Shlyakhova, Alexander Kolubaev, Evgeny A. Kolubaev, Sergey Grigorievich Psakhie, Gennadii Rudenskii, Alexander G. Chernyavsky, and Vitalii Lopota. "Microstructure Features of Aluminum Alloys Welded Joint Obtained by Friction Stir Welding." Advanced Materials Research 872 (December 2013): 174–79. http://dx.doi.org/10.4028/www.scientific.net/amr.872.174.

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The paper presents a metallographic study of aluminum alloy welds produced by friction stir welding. The weld structure is described for two alloys: Al-Cu and Al-Mg. It is shown that friction stir welding provides a fine-grained structure of the weld. The phase composition of the weld metal for the studied alloys is defined. Differences in the structure and distribution of second-phase particles in the weld metal are shown. The weld zone of Al-Cu alloy consists of equal size grains, with intermetallic particles located along the grain boundaries. The weld structure of Al-Mg alloy is banded, with alternating layers consisting of different size grains.

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Xie, Xiao Hua, Le Ping Chen, Cheng Bo Xiao, and Xin Tang. "Effects of Mechanical Vibration and Pouring Temperature on Solidified Structure of Superalloy K4169." Advanced Materials Research 842 (November 2013): 332–36. http://dx.doi.org/10.4028/www.scientific.net/amr.842.332.

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The influences of different vibration amplitude and pouring temperature on solidified structure of superalloy K4169 under the action of mechanical vibration were investigated. The vibration amplitudes and pouring temperatures used were 1.5, 1.75 and 2 mm and 1380, 1430, 1480 and 1530°C, respectively. The experimental results show that application of mechanical vibration leads to increase in grain refinement and proportion of equiaxed grains of superalloy K4169. The dendrite growth is restrained and the microstructure is changed from well-developed dendrite grains to fine equiaxed grains. Grain size of the alloy decreases as vibration amplitude increases. With the increase of the pouring temperature, grain size of the alloy increases firstly, then decreases and the turning point is 1430°C. When the pouring temperature is 1380°C, grain size of the alloy with mechanical vibration treatment is the finest.

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Zhidkov, M. V., A. E. Ligachev, Yu R. Kolobov, G. V. Potemkin, and G. E. Remnev. "Effect of high-power ion beams on the surface topography and structure of submicrocrystalline titanium alloy subsurface layers." Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Universitiesʹ Proceedings. Powder Metallurgy аnd Functional Coatings), no. 4 (December 15, 2018): 82–91. http://dx.doi.org/10.17073/1997-308x-2018-4-82-91.

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The study covers the topography and structural phase state of VT1-0 and VT6 submicrocrystalline titanium alloy subsurface layers irradiated by high power pulsed carbon ion beams (ion energy is 250 keV, pulse duration is ~100 ns, pulse current density is 150–200 A/cm2; surface energy density of a single pulse is j ~ 3 J/cm2 when irradiating VT1-0 titanium alloy samples and j ~ 1 J/cm2 when processing VT6 titanium alloy samples; pulse number is 1, 5, 10, and 50). The surface of samples was subjected to preliminary mechanical grinding and polishing before irradiation. It was shown that surface defects are formed on the surface of the alloys after irradiation, namely craters of different shapes and geometries with a diameter from fractions of a micron to 80–100 μm. At the same time, the grain structure in the subsurface layer becomes more homogeneous in terms of grain size and equiaxial properties. The initial state of titanium alloys is characterized by a fairly homogeneous structure with an average grain size of ~0,31 μm for VT1-0 and ~0,9 μm for VT6. After one irradiation pulse, grain growth to 0,54 μm in the transverse direction is observed in the subsurface layer of the VT1-0 alloy (j ~ 3 J/cm2), while grain size decreases to ~ 0,54 μm in the VT6 alloy (j ~ 1 J/cm2). After 50 pulses, the average grain size in the subsurface layer reaches ~2,2 μm for the VT1-0 alloy and ~1,6 μm for VT6. It should be noted that a rather uniform structure with equiaxed grains is formed as early as after treating with 1 high power ion beam pulse.

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Serebryany, Vladimir N., Grigory S. Djyakonov, Gennady A. Salishchev, Vladimir I. Kopylov, and Sergey V. Dobatkin. "Texture and Structure Study of AZ41 Alloy after ECAP and Annealing." Materials Science Forum 753 (March 2013): 469–72. http://dx.doi.org/10.4028/www.scientific.net/msf.753.469.

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Equal channel angular pressing (ECAP) of magnesium alloys dramatically effects the texture and structure of the alloys due to processes of severe plastic deformation and dynamic recrystallization. Changes in texture, structure and tensile properties of AZ41 alloy after ECAP by Bc regime with 4 passes at a temperature of 245° C and subsequent annealing were studied. Evaluation of texture and structure was performed using the orientation distribution function (ODF) restore from the X-ray direct pole figures and the large number of individual orientations measured by the EBSD method. After ECAP the structure of the dynamically recrystallized fine grains with an average size of about 2,9 μm was revealed. The ratio of the volume fraction of low angle grain boundaries (LAGBs) to the high angle grain boundaries (HAGBs) constituted as 1:3. The formation of few basal texture, tilted by 45 ÷ 55 ° to the pressing direction was also found. Subsequent annealing increases the grain size to 10 μm, the fraction of HAGBs - up to 85% and practically does not change the texture type. These changes in structural parameters improve considerably the low-temperature ductility of AZ41 alloy.

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El-Aziz, Khaled Abd, Emad M. Ahmed, Abdulaziz H. Alghtani, Bassem F. Felemban, Hafiz T. Ali, Mona Megahed, and Dalia Saber. "Development of Al–Mg–Si alloy performance by addition of grain refiner Al–5Ti–1B alloy." Science Progress 104, no. 2 (April 2021): 003685042110294. http://dx.doi.org/10.1177/00368504211029469.

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Aluminum alloys are the most essential part of all shaped castings manufactured, mainly in the automotive, food industry, and structural applications. There is little consensus as to the precise relationship between grain size after grain refinement and corrosion resistance; conflicting conclusions have been published showing that reduced grain size can decrease or increase corrosion resistance. The effect of Al–5Ti–1B grain refiner (GR alloy) with different percentages on the mechanical properties and corrosion behavior of Aluminum-magnesium-silicon alloy (Al–Mg–Si) was studied. The average grain size is determined according to the E112ASTM standard. The compressive test specimens were made as per ASTM: E8/E8M-16 standard to get their compressive properties. The bulk hardness using Vickers hardness testing machine at a load of 50 g. Electrochemical corrosion tests were carried out in 3.5 % NaCl solution using Autolab Potentiostat/Galvanostat (PGSTAT 30).The grain size of the Al–Mg–Si alloy was reduced from 82 to 46 µm by the addition of GR alloy. The morphology of α-Al dendrites changes from coarse dendritic structure to fine equiaxed grains due to the addition of GR alloy and segregation of Ti, which controls the growth of primary α-Al. In addition, the mechanical properties of the Al–Mg–Si alloy were improved by GR alloy addition. GR alloy addition to Al–Mg–Si alloy produced fine-grained structure and better hardness and compressive strength. The addition of GR alloy did not reveal any marked improvements in the corrosion properties of Al–Mg–Si alloy.

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Kusuhara, Hiroaki, Munetoshi Noguchi, Masafumi Noda, Hisashi Mori, and Kunio Funami. "Effect of Fine Grain on Mechanical Properties of A6N01 Alloy." Materials Science Forum 753 (March 2013): 501–4. http://dx.doi.org/10.4028/www.scientific.net/msf.753.501.

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The good formability and corrosion resistance of 6N01 Al alloy allow it to be utilized in high-speed train systems, and weight reduction of railway vehicles is possible by improving the strength of this alloy. This study examined the effect of the fine-grained structure on the mechanical properties of the alloy formed by a combination of heat treatment and severe plastic deformation such as forging and rolling. The role of the fine-grained structure in determining the plastic formability was also investigated. The 0.2% proof stress and tensile strength of the heat-treated and multi-axial alternative forging (MAF) processed materials were both greater than 300 MPa. Subsequent cold rolling of these alloys increased both the 0.2% proof stress and tensile strength to over 450 MPa with a grain size of less than 1 μm. The fine-grained structure was confirmed to be effective in improving the strength of the 6N01 Al alloy.

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Cirovic, Natasa, Pavle Spasojevic, Lenka Ribic-Zelenovic, Pavle Maskovic, Aleksa Maricic, and Miroslav Spasojevic. "Synthesis, structure and properties of nickel-iron-tungsten alloy electrodeposits - Part II: Effect of microstructure on hardness, electrical and magnetic properties." Science of Sintering 48, no. 1 (2016): 1–16. http://dx.doi.org/10.2298/sos1601001c.

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Nanostructured nickel-iron-tungsten alloys were produced by electrodeposition from an ammoniacal citrate bath. The tungsten content of the alloy ranged from 0.8 wt.% to 11 wt.%, and the crystal grain size of the FCC phase of the solid solution of iron and tungsten in nickel was between 14 nm and 3.3 nm. The amorphous phase content of the alloy increases with decreasing crystal grain size. As the amorphous phase content increases, the magnetization, electrical conductivity and hardness of the alloy decrease. Annealing the alloy to crystallization temperature results in structural relaxation during which the alloy undergoes short-range ordering in conjunction with decreases in the density of chaotically distributed dislocations and internal microstrain level, which increases the exchange integral value, the electronic density of states at the Fermi level, the mean free path of electrons, the ordering and the mean size of cluster in the sliding plane and results in more uniform orientation of dipole moments of certain nanoparticles. These changes: a) increase the mobility of magnetic domain walls, facilitate the orientation of domains in the external magnetic field and cause an increase in magnetization; b) cause a decrease in electrical resistance, and c) impede the sliding of grain boundaries and increase the hardness of the alloy. Annealing the alloys at temperatures above 400?C results in amorphous phase crystallization and larger crystal grains of the FCC phase, along with a decrease in the density of chaotically distributed dislocations and a decrease in internal microstrain level. The formation of larger crystal grains reduces the hardness of the alloy, decreases its specific electrical resistance and impedes both the orientation of certain magnetic domains and the shift of walls of already oriented domains, thus inducing a decrease in magnetization. The heat released during the milling of Ni87.3Fe11.3W1.4 alloy with FCC-phase crystal grains 8.8 nm in average size causes amorphous phase crystallization, FCC crystal grain growth and an increase in magnetization. Alloys with relatively high tungsten content (11 wt. %) have an inhomogeneous composition, a high proportion of the amorphous phase and FCC crystal grains with an average size of 3.3 nm. This microstructure results in magnetic domains that have different and relatively low thermal stabilities and relatively low degrees of magnetization.

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Shepelevich, V. G. "Grain Structure of Rapidly Solidified Alloy Sn32Bi52Pb16." Inorganic Materials: Applied Research 9, no. 4 (July 2018): 609–11. http://dx.doi.org/10.1134/s2075113318040366.

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Kekule, Tomáš, Hana Kudrnova, Martin Vlach, Bohumil Smola, and Ivana Stulíková. "Development of Microstructure and Properties of Mg-Y-(Nd)-Zn Alloys during Heat and Mechanical Treatment." Defect and Diffusion Forum 369 (July 2016): 157–62. http://dx.doi.org/10.4028/www.scientific.net/ddf.369.157.

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This work is focused on development of microstructure and properties of Mg-Y-Zn and Mg-Y-Nd-Zn alloys during heat and mechanical treatment. In the as-cast state both alloys exhibit almost equiaxed grains with little larger size in Mg-Y-Zn alloy and grain boundaries decorated by different structures - long period ordered structure (LPSO) was detected in Mg-Y-Zn alloy and eutectics of Mg3Nd type structure in alloy with Nd addition. A high density of stacking faults is evident in both alloys. Both alloys were repeatedly isochronally heat treated from room temperature up to 440 °C. Resistivity and microhardness measurement was performed after each heating step. Stacking faults persist both annealings in both alloys and microhardness development shows no remarkable differences. LPSO in Mg-Y-Zn alloy disappears after the first annealing and was again detected after repeated annealing up to 340 °C. After the whole treatment no grain growth appeared. Differential scanning calorimetry measurement was performed at both repeatedly heated alloys up to 540 °C. There are three exothermic peaks in DSC curves of Mg-Y-Zn alloys that can be ascribed to embedding solute atoms in stacking faults, LPSO development and transformation and coarsening of grain boundary particles. DSC curves of Mg-Y-Nd-Zn alloy exhibit two exothermic peaks that probably correspond to precipitation of basal plates of γ ́and γ phase. Measurement of microhardness was performed after sequential deformation of both alloys in the as-cast state. The alloys were cold rolled in steps of 0,9 % thickness reduction up to cracks formation. Strengthening of both alloys is very similar but formation of cracks in the alloy with Nd addition begins after a lower reduction (about 11 %) compared to Mg-Y-Zn alloy (about 15 %).

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26

Ryspaev, Talant, M. Janecek, Robert Kral, Volker Wesling, and Lothar Wagner. "Processing, Superplastic Properties and Friction Stir Welding of Fine-Grained AZ31, AZ91, AE42 and QE22 Magnesium Alloys." Materials Science Forum 838-839 (January 2016): 220–24. http://dx.doi.org/10.4028/www.scientific.net/msf.838-839.220.

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The grain refinement after thermo-mechanical treatment (TMT) was investigated in AZ91, AE42, und QE22 magnesium alloys. The optimal over-aging temperature was determined to be 300 °C in the case of AZ91 and AE42 alloys and 350 °C for QE22 alloy. After optimized TMT, the average grain sizes were 13.5 µm (AE42), 11.1 µm (AZ91) and 1.9 µm (QE22). The QE22 alloy exhibited the superior superplastic properties, with maximum elongation to failure 750 % and strain rate sensitivity parameter m=0.73. The Friction Stir Welding showed that the original base material grain structure of the alloys AZ31 and AZ91 replaced by ultrafine grains in the stir zone. The purpose of the present paper is to present the results of the grain refinement in magnesium alloys by thermo mechanical treatment and stir welding.

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27

Ueki, Kosuke, Soh Yanagihara, Kyosuke Ueda, Masaaki Nakai, Takayoshi Nakano, and Takayuki Narushima. "Improvement of Strength and Ductility by Combining Static Recrystallization and Unique Heat Treatment in Co-20Cr-15W-10Ni Alloy for Stent Application." Materials Science Forum 1016 (January 2021): 1503–9. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.1503.

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The Co-20Cr-15W-10Ni (CCWN, mass%) alloy has excellent corrosion resistance and strength-ductility balance and is applied in almost all balloon-expandable stent platforms. To further reduce the invasiveness of stent placement, it is necessary to reduce the diameter of the stent. That is, both high strength and high ductility should be achieved while maintaining a low yield stress. In our previous studies, it was discovered that low-temperature heat-treatment (LTHT) at 873 K improves the elongation of the CCWN alloy. In this study, we focused on the grain refinement by swaging and static recrystallization to improve the strength of the alloy. The as-swaged alloy was recrystallized at 1373–1473 K for 100–300 s, followed by LTHT. A fine grain structure with an average grain size of 3–17 μm was obtained by static recrystallization. The η-phase (M12X-M6X type precipitates, M: metallic elements, X: C and/or N) formed during the recrystallization at 1373–1448 K. The alloys recrystallized at 1448 and 1473 K had a homogeneous structure with a small variation in the grain size. On the other hand, the alloys recrystallized at 1373 and 1423 K had an inhomogeneous structure in which fine and coarse grains were mixed. Both the strength and ductility of the CCWN alloy were improved by combining high-temperature short-time recrystallization and LTHT.

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28

Morishita, Hironori, Hisao Esaka, and Kei Shinozuka. "Crystallographic Investigation of the Initial Solidification Grain Structure in Al-Si Alloy." Materials Science Forum 879 (November 2016): 1328–31. http://dx.doi.org/10.4028/www.scientific.net/msf.879.1328.

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As-solidified structure of an ingot is composed of the chill, columnar and equiaxed zones. The whole solidified structure is strongly affected by the chill crystals. Some initial solidification grains have been observed on the ingot surface and thought to be traces of the nucleation point. The aim of this study is, therefore, to develop the experiment technique to make one ‘grain’ and to crystallographically investigate the initial solidification grain using EBSD analysis. In order to start solidification at a very specified position, a small metallic protrusion was installed on an insulating plate. Al-6 wt%Si alloy was melted at 800 °C and was poured on the metallic protrusion. In this study, the amount of protrusion was varied to investigate the growth mechanism of the initial solidification grain. The longitudinal cross section of the specimen was observed by an optical microscope, a scanning electron microscope. The starting position of solidification was the area that was on the metallic protrusion. In this initial solidification grain, it was difficult to observe the dendritic structure. The shape of this grain was about hemispherical. The grain area seemed to increase with increasing the amount of protrusion. The results of EBSD analysis showed that almost all initial solidification grains were composed by several crystals. The reason of this is that the nucleation frequency may increase with the amount of protrusion. The dendrite grew radially from the initial solidification grain continuously. The crystallographic structure was also continuous on the boundary of the initial solidification grain.

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29

Xie, Xiao Hua, Quan Zhou, Cheng Bo Xiao, and Xin Tang. "Effect of Low-Voltage Pulsed Magnetic Field on Solidified Structure of Superalloy K4169." Applied Mechanics and Materials 423-426 (September 2013): 725–29. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.725.

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Effects of different pulse voltage and frequency on solidified structure of superalloy K4169 under low-voltage pulsed magnetic field (LVPMF) were investigated in this paper, and the related mechanism was also discussed. The experimental results show that grain of superalloy K4169 can be refined greatly by LVPMF treatment during the course of solidification. Growth of dendrite is restrained and primary grain is changed from large dendrites to smaller equiaxed grains. When the pulse voltage is at 0-280V, grain size of the alloy decreases as pulse voltage increases, and primary dendrites are fractured from well-developed dendrites into fine equiaxed grains and non-dendritic structures. When the pulse frequency is at 0-5Hz, the increase of pulse frequency enhances the refinement effect of LVPMF processing. With the increase of the pulse frequency, grain size of the alloy increases.

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30

Morikawa, Tatsuya, Daisuke Kinoshita, Yoshihito Kawamura, and Kenji Higashida. "Fine-Grained Structure in Extruded Magnesium Alloy with Long-Period Stacking Order Phase." Materials Science Forum 561-565 (October 2007): 905–8. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.905.

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Microstructures developed by warm extrusion for Mg97Zn1Y2 alloy including long-period stacking order (LPSO) phase have been investigated using SEM and TEM. The extruded magnesium alloy with LPSO phase exhibits high strength and sufficient ductility. Such superior mechanical properties appear by warm extrusion around the temperature of 623K. The microstructure of the extruded alloy consists of matrix of fine-grained hcp phase and elongated grains with fine-lamellae including LPSO phase. The grain size of hcp matrix was about 1μm, indicating that remarkable grain refinement was occurred by extrusion since the grain size of as-cast alloy was about 500μm. Special attention has been paid on the enrichment of solutes at stacking faults and grain boundaries in the fine-grained matrix, which would contribute not only to the strengthening but also to the stability of fine-grained structure because of its role of an inhibiter against grain coarsening.

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31

Chen, Qipeng, and Houfa Shen. "Direct Macroscopic Modeling of Grain Structure and Macrosegregation with a Cellular Automaton–Finite Element Model." Metals 9, no. 2 (February 2, 2019): 177. http://dx.doi.org/10.3390/met9020177.

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Grain structure and macrosegregation are two main factors determining mechanical properties of components and are strongly coupled during alloy solidification. A two-dimensional (2D) cellular automaton (CA)–finite element (FE) model is developed to achieve a direct macroscopic modeling of grain structure and macrosegregation during the solidification of binary alloys. With the conservation equations of mass, momentum, energy, and solute solved by a macroscopic FE model and the grain structure described by a microscopic CA model, a two-way coupling between the CA and FE models is applied. Furthermore, the effect of the fluid flow on the dendrite tip growth velocity is considered by modified dendrite tip growth kinetics. The CAFE model is applied to a quasi-2D benchmark solidification experiment of a Sn–3.0wt.%Pb alloy, and the grain structure and macrosegregation are predicted simultaneously. It is demonstrated that the model has a capacity to describe the undercooling ahead of the growth front. The growth directions of columnar grains, grain sizes, and columnar-to-equiaxed transition (CET) position are obviously modified by the fluid flow, and obvious segregated channels almost aligned with the orientations of the columnar grains are found. Qualitatively good agreement is obtained between the predicted segregation profiles and experimental measurements.

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32

Nosova, E. A., A. A. Fadeeva, and M. A. Starodubtseva. "Research of grain size homogeneity effect on sheet stamping ability characteristics of Al2Mg and Al6Mg alloys." Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy, no. 3 (June 19, 2019): 47–54. http://dx.doi.org/10.17073/0021-3438-2019-3-47-55.

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The quality of products made of sheet aluminum alloys strongly depends on the technological features of the sheet stamping process, as well as on the structure of sheet semi-finished products. The grain size and grain structure uniformity are among the key structural features that influence stampability. A method is proposed and the homogeneity of the grain structure is evaluated. Stampability of Al2Mg and Al6Mg aluminium alloys was evaluated based on measurements of the spring back index, minimum bending radius, stamping ratio, and Martens strain index. Cold work (with a strain degree of 20 %) and subsequent recrystallization annealing at temperatures of 250, 350 and 450 °C for 1 h were used to obtain a grain structure of (26,8 Ѓ} 7,4)÷(126 Ѓ} 43) μm (Al6Mg alloy) and (120 Ѓ} 11)÷(264 Ѓ} 130) μm (Al2Mg alloy) in size. As a result of processing, the effect of the initial grain size was revealed: the coarser structure of the Al2Mg alloy led to a larger grain size after strain and annealing. It was found that an increase in the grain size in both alloys leads to an increase in the Martens index and a decrease in the stamping ratio, which indicates higher stampability of the alloys in the drawing operations of sheet stamping. In the Al2Mg alloy, an increase in the grain size leads to a decrease in the spring back index by 1,5–1,7 times, and an increase in the minimum bending radius. In the Al6Mg alloy, an increase in the grain size leads to an increase in the spring back index by 1,1–1,2 times, and a decrease in the minimum bending radius. The Al6Mg minimum bending radius remains higher compared to Al2Mg regardless of the grain size. Grain size inhomogeneity in the Al6Mg alloy causes an increase in the Martens index and minimum bending radius, and a decrease in the stamping ratio. In the Al2Mg alloy, grain size inhomogeneity causes an increase in the Martens index and minimum bending radius, and a decrease in the stamping ratio. For the spring back index, the increase in grain size inhomogeneity causes a high scatter of data. In the Al6Mg alloy, the low annealing temperature led to the preservation of the non-recrystallized structure, which influenced the decrease in stampability.

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33

Zuo, Yu Bo, Zhi Hao Zhao, Qing Feng Zhu, Xiang Jie Wang, and Jian Zhong Cui. "Preparing Large Sized Billet of High Strength Aluminum Alloy with the Application of Low Frequency Electromagnetic Field." Advanced Materials Research 472-475 (February 2012): 723–26. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.723.

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Grain refinement is quite important for producing 7050 alloy billet especially in large scale. Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy Φ500 mm billets and study the effect of electromagnetic field on the microstructure. The sound Φ500 mm billets of 7050 alloys without any grain refiner can be successfully prepared by the LFEC process. The results show that low frequency electromagnetic field has a significant grain refining effect on 7050 alloy and can effectively eliminate feather grain structure. The microstructures of LFEC ingot from the border to the center of the cross section are all equiaxed grains and are finer and more uniform than that of conventional direct chill (DC) cast billets. The LFEC process also shows a strong power to eliminate hot tearing during casting large sized billet of high strength aluminium alloy.

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34

Chen, Qipeng, Hongxiang Li, and Houfa Shen. "Transient Modeling of Grain Structure and Macrosegregation during Direct Chill Casting of Al-Cu Alloy." Processes 7, no. 6 (June 1, 2019): 333. http://dx.doi.org/10.3390/pr7060333.

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Grain structure and macrosegregation are two important aspects to assess the quality of direct chill (DC) cast billets, and the phenomena responsible for their formation are strongly interacted. Transient modeling of grain structure and macrosegregation during DC casting is achieved with a cellular automaton (CA)–finite element (FE) model, by which the macroscopic transport is coupled with microscopic relations for grain growth. In the CAFE model, a two-dimensional (2D) axisymmetric description is used for cylindrical geometry, and a Lagrangian representation is employed for both FE and CA calculations. This model is applied to the DC casting of two industrial scale Al-6.0 wt % Cu round billets with and without grain refiner. The grain structure and macrosegregation under thermal and solutal convection are studied. It is shown that the grain structure is fully equiaxed in the grain-refined billet, while a fine columnar grain region and a coarse columnar grain region are formed in the non-grain-refined billet. With the increasing casting speed, grains become finer and grow in a direction more perpendicular to the axis, and the positive segregation near the centerline becomes more pronounced. The increasing casting temperature makes grains coarser and the negative segregation near the surface more pronounced.

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35

Anil Kumar, V., M. K. Karthikeyan, Rohit Kumar Gupta, P. Ramkumar, and P. P. Sinha. "Equal Channel Angular Pressing of Al Alloy AA2219." Advanced Materials Research 67 (April 2009): 53–58. http://dx.doi.org/10.4028/www.scientific.net/amr.67.53.

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Severe plastic deformation processes (SPD) are gaining importance as advanced materials processing techniques and hold immense potential in obtaining ultra fine-grained high strength materials. Among the SPD techniques, Equal channel angular pressing (ECAP) has its own merits to produce materials with ultra fine grains in bulk with better mechanical properties. The material deforms with high level of plastic strain inside the channel resulting in grain refinement of the output material with improvement in mechanical properties. A very viable die configuration was conceptualized and die was made with 1200 channel angle. Processing of 25 mm dia. of Al alloy AA2219 at room temperature was successfully carried out and grain refinement was observed. The mechanism of grain refinement has been studied using optical and transmission electron microscopy (TEM). It was observed that low energy dislocation structure (LEDS) forms concurrently with sub-grain structure due to dislocation rearrangements, which provide stability to the evolving sub-grain structure. Dislocation mobility is hindered by the presence of precipitates and / or intermetallic dispersoids present in the matrix and results in presence of dislocations in grain interiors. The pile up of dislocations at intermetallic dispersoids was confirmed from the dark field TEM micrographs. Present paper describes the experimental procedure and followed to attain severe plastic deformation through ECAP. Increase in hardness as well as refinement in the grain size after 5-passes have been discussed in light of extensive optical and TEM. The mechanisms of grain refinement to achieve nano-grained structure and strengthening accrued from the grain refinement through ECAP has been discussed.

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36

Meng, Shuaiju, Hui Yu, Haisheng Han, Jianhang Feng, Lixin Huang, Lishan Dong, Xiaolong Nan, Zhongjie Li, Sung Hyuk Park, and Weimin Zhao. "Effect of Multi-Pass Caliber Rolling on Dilute Extruded Mg-Bi-Ca Alloy." Metals 10, no. 3 (March 2, 2020): 332. http://dx.doi.org/10.3390/met10030332.

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A Mg-1.32Bi-0.72Ca (BX11) alloy having bimodal grain structure was successfully prepared by a novel processing route of combining extrusion and three-pass caliber rolling. The first extruded and then caliber-rolled (E-CRed) alloy demonstrates a necklace-like grain structure with ultrafine grains formed around the microscale deformed grains, which is remarkably different from the uniform microstructure of the as-extruded alloy. In addition, the E-CRed BX11 alloy exhibits strong basal texture which is mainly original from the microscale deformed grains. Furthermore, the E-CRed BX11 alloy demonstrates excellent comprehensive mechanical properties, with an ultra-high yield strength of 351 MPa and a good elongation to failure of 13.2%. The significant strength improvement can be mainly attributed to the significant grain refinement and much stronger basal texture compared with the as-extruded sample.

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37

Goloborodko, Alexandre, Oleg Sitdikov, Hiromi Miura, and Taku Sakai. "Fine-Grained Structure Formation in 7475 Al Alloy during Hot Multidirectional Forging." Materials Science Forum 512 (April 2006): 79–84. http://dx.doi.org/10.4028/www.scientific.net/msf.512.79.

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Effect of strain rate on grain refinement was studied in multidirectional forging (MDF) of a coarse-grained 7475 Al alloy at 490oC under strain rates of 3 × 10-4 s-1 and 3 × 10-2 s-1. At a strain rate of 3 × 10-4 s-1, the stress – strain ( σ - ε) behavior shows significant work softening just after yielding and a steady-state flow at higher strains. The structural changes are characterized by development of deformation bands at early stages of deformation, followed by formation of a fine grain structure in high strain in the whole material. The volume fraction of new grains increases with strain and approaches a value of about 0.85 over a strain of 3. At a higher strain rate of 3 × 10-2 s-1, in contrast, a steady-state flow following small flow softening appears at a relatively low strain. New grains are formed during steady state flow along original grain boundaries and the volume fraction reaches below 0.2 even in high strain. The occurrence conditions and the mechanisms of grain refinement are discussed in detail.

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38

Wang, Xiaoya, Jiantang Jiang, Guoai Li, Wenzhu Shao, and Liang Zhen. "Precipitation during Quenching in 2A97 Aluminum Alloy and the Influences from Grain Structure." Materials 14, no. 11 (May 25, 2021): 2802. http://dx.doi.org/10.3390/ma14112802.

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The quench-induced precipitation and subsequent aging response in 2A97 aluminum alloy was investigated based on the systematic microstructure characterization. Specifically, the influence on precipitation from grain structure was examined. The results indicated the evident influence from the cooling rate of the quenching process. Precipitation of T1 and δ′ phase can hardly occur in the specimen exposed to water quenching while become noticeable in the case of air cooling. The yield strength of 2A97-T6 alloy de-graded by 234 MPa along with a comparable elongation when water quenching was replaced by air cooling. Sub-grains exhibited a much higher sensitivity to the precipitation during quenching. The presence of dislocations in sub-grains promoted the quench-induced precipitation by acting as nucleation sites and enhancing the diffusion of the solute. A quenching rate of 3 °C/s is tolerable for recrystallized grains in 2A97 Al alloy but is inadequate for sub-grains to inhibit precipitation. The study fosters the feasibility of alleviating quench-induced precipitation through cultivating the recrystallization structure in highly alloyed Al–Cu–Li alloys.

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39

Burhan, N., and Michael Ferry. "Changes in Grain Size Distribution of a Submicron Grained Al-Sc Alloy during High Temperature Annealing." Materials Science Forum 519-521 (July 2006): 1617–22. http://dx.doi.org/10.4028/www.scientific.net/msf.519-521.1617.

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Severe plastic straining is an established method for producing submicron grain (SMG) structures in alloys. However, the development of such a fine grained structure in single-phase alloys is usually futile if they are to be exposed or processed at elevated temperatures. This is a direct consequence of the natural tendency for rapid and substantial grain coarsening which completely removes the benefits obtained by grain refinement. This problem may be avoided by the introduction of nanosized, highly stable particles in the metal matrix. In this work, a SMG structure was generated in an Al-0.3 wt.% Sc alloy by Equal Channel Angular Pressing (ECAP). The alloy was prepared initially to produce a fine grained microstructure exhibiting a large fraction of high angle grain boundaries and a dispersion of nanosized Al3Sc particles. The evolution of microstructure during annealing at temperatures up to 550 °C was examined in detail and grain size distributions generated from the data. It was shown that grain coarsening is rapid at temperatures above 450 °C and the initial log-normal grain size distribution exhibiting low variance and skewness was altered considerably. The statistical information generated from the grain size distributions confirms that discontinuous grain coarsening occurs in this alloy only at temperatures greater than 500 °C.

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40

Wang, Zhen Qing, X. H. Zuo, Z. X. Yang, and H. R. Geng. "Grain Refinement of Zn-25Al Alloy through the Addition of Zn-6Ti Master Alloy." Advanced Materials Research 562-564 (August 2012): 322–25. http://dx.doi.org/10.4028/www.scientific.net/amr.562-564.322.

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In this paper, Zn-6Ti master alloy was produced and characterized by XRD and SEM. It was found that α-Al dendritic grains in Zn-25Al alloy were remarkably refined after the addition of Zn-6Ti master alloy, with the size remarkably reduced and the morphology changed from complex dendrite to rose-like or granular (equiaxed particle) structure. Lower solidification temperature of the Zn-Al melt was found to further promote the formation of granular (equiaxed particle) α-Al grain in Zn-25Al alloy with the addition of Zn-6Ti master alloy. The mechanism for the grain refinement is discussed based on the SEM observation of TiAl3-xZnxparticles at the center of α-Al grain in Zn-25Al alloy.

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41

Wang, Guang Zong, Da Quan Li, and Qiang Zhu. "Investigation on the Physical and Chemical Grain Refinement of the Mg-10Sm Alloy." Materials Science Forum 816 (April 2015): 459–64. http://dx.doi.org/10.4028/www.scientific.net/msf.816.459.

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In this paper the physical and chemical grain refining of the Mg-10Sm alloy was investigated. Physical grain refinement was achieved by strongly shearing the melt above the liquidus temperature using a twin-screw string device and then cast at the near liquidus temperature. Chemical grain refiner was added into Zr master alloy in the melt. Casting the Mg-10Sm alloy at 730°C produced an extremely coarse microstructure consisting of huge dendritic grains. The physical grain refinement greatly refined the dendritic grains to smaller rosette grains, being reduced from several millimeters to about 200μm. Chemical grain refinement produced fine and equiaxed grain structure with size of approximated 111μm. Combination of the physical and chemical grain refinement creates more significant refining effect than either of the two methods.

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42

Jia, Hai Long, Knut Marthinsen, and Yan Jun Li. "Al-5Cu Alloy Processed by Equal-Channel Angular Pressing." Materials Science Forum 879 (November 2016): 843–48. http://dx.doi.org/10.4028/www.scientific.net/msf.879.843.

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An ECAP (equal channel angular pressing) processed UFG Al-5Cu alloy was characterized by electron backscatter diffraction (EBSD). It is revealed that a bimodal grain structure, i.e. ultrafine grains accompanied by micron-sized grains was developed after 4 passes. A high strength (~501 MPa) and a relatively large elongation to failure (~28%) with ~5% uniform elongation were achieved simultaneously after 4 passes of ECAP. The high strength is due to a combination of strengthening by solute, high density of dislocations and ultrafine grains. The enhancement of uniform elongation is primarily due to the enhanced work hardening resulted from the solute Cu content and the bimodal grain structure. The large post-uniform elongation is attributed to the high strain rate sensitivity of the UFG Al-5Cu alloy. More importantly, the present work revealed that during ECAP high solid solution content of Cu and coarse secondary phase particles can introduce inhomogeneous deformation resulting in a desirable bimodal grain structure, which can be utilized as a strategy to gain both high strength and relatively good ductility.

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43

Fonda, R. W., and D. E. Luzzi. "Morphology and atomic structure of segregated grain boundaries in Cu-Sb." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 1 (August 1992): 254–55. http://dx.doi.org/10.1017/s0424820100121673.

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The properties of polycrystalline materials are strongly dependant upon the strength of internal boundaries. Segregation of solute to the grain boundaries can adversely affect this strength. In copper alloys, segregation of either bismuth or antimony to the grain boundary will embrittle the alloy by facilitating intergranular fracture. Very small quantities of bismuth in copper have long been known to cause severe grain boundary embrittlement of the alloy. The effect of antimony is much less pronounced and is observed primarily at lower temperatures. Even though moderate amounts of antimony are fully soluble in copper, concentrations down to 0.14% can cause grain boundary embrittlement.

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44

Horita, Z., D. J. Smith, M. Furukawa, M. Nemoto, R. Z. Valiev, and T. G. Langdon. "High-resolution EM study of submicrometer-grained Al-Mg solid solution alloys." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 524–25. http://dx.doi.org/10.1017/s0424820100138993.

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It is possible to produce metallic materials with submicrometer-grained (SMG) structures by imposing an intense plastic strain under quasi-hydrostatic pressure. Studies using conventional transmission electron microscopy (CTEM) showed that many grain boundaries in the SMG structures appeared diffuse in nature with poorly defined transition zones between individual grains. The implication of the CTEM observations is that the grain boundaries of the SMG structures are in a high energy state, having non-equilibrium character. It is anticipated that high-resolution electron microscopy (HREM) will serve to reveal a precise nature of the grain boundary structure in SMG materials. A recent study on nanocrystalline Ni and Ni3Al showed lattice distortion and dilatations in the vicinity of the grain boundaries. In this study, HREM observations are undertaken to examine the atomic structure of grain boundaries in an SMG Al-based Al-Mg alloy.An Al-3%Mg solid solution alloy was subjected to torsion straining to produce an equiaxed grain structure with an average grain size of ~0.09 μm.

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45

Li, Jian Ping, Gordon W. Lorimer, Joseph D. Robson, and B. Davis. "The Microstructures of As-Cast Mg-Zr and Mg-Mn Alloys." Materials Science Forum 488-489 (July 2005): 329–32. http://dx.doi.org/10.4028/www.scientific.net/msf.488-489.329.

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The as-cast microstructures of two dilute Mg-Zr and three dilute Mg-Mn alloys were studied using optical microscopy and scanning electron microscopy, including EDX analysis. The results show that the as-cast microstructure of the Mg-Zr alloys was composed of non-dendritic, equiaxed Mg grains, with a few Zr particles within the Mg grains and along grain boundaries. The grain size of the Mg-Zr alloy was significantly reduced by the Zr addition and a fine grain structure was achieved when the zirconium concentration was above 0.4wt. %. The as-cast structure of the Mg- Mn alloys contained columnar, dendritic grains. Two types of Mn particles (equiaxed large particles and rod-like or plate-like small particles) were observed in the as-cast Mg-Mn alloys. The volume fraction of particles and the size differences between the large and small particles increased with an increase of Mn concentration.

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46

Lee, Byoung Soo, and Hoon Cho. "Influence of ECAP Routes on the Microstructure and Mechanical Properties of Hot Extruded 3003 Al Alloy." Solid State Phenomena 124-126 (June 2007): 1397–400. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.1397.

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The microstructures and mechanical properties of unidirectional deformation structured Al alloy during ECAP with various deformation routes were investigated. In order to fabricate unidirectional deformation structure for Al alloy, hot extrusion was carried out. It was found that the deformation route A in ECAP routes is the dominant route for the grain refinement and strengthening. In deformation route A, the high strength ultra-fine grained Al alloy with a grain size of ~ 200 nm was obtained due to the accumulation of consecutive strain process. In contrast, the strength of ECAP’ed Al alloy produced via deformation route C was greatly increased after one pass because the grains were strained and cancelled each pass. By contrast, the equiaxed grains were obtained in deformation route BC because the sample was rotated 90 O in the same sense in each pass. The deformation route BC was superior to the deformation route C because the deformation route BC was more favorable than the deformation route C in the accumulation of consecutive strain. It is also found that unidirectional deformation structured Al alloy via hot extrusion shows similar grain refinement tendency with equiaxed structured Al alloy during ECAP processing.

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47

Tunca, Bensu, Emin Erkan Aşik, G. Ipek Nakaş, and Şakir Bor. "Recrystallization of AZ31 Alloy." Materials Science Forum 783-786 (May 2014): 497–502. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.497.

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Magnesium alloys are extensively used in electronics, automotive and aerospace industries due to their low densities and high specific strengths. However, limited deformability of magnesium alloys at room temperature restricts the applications. Grain refinement and texture weakening as a result of recrystallization can be used to enhance the deformability of these alloys. In this study, recrystallization behavior of cold rolled and swaged AZ31 alloy is investigated at different temperatures in the range of 200-300°C. Effects of unidirectional and complex deformation modes on recrystallization behavior and microstructure development are studied. Microstructural analyses consisted of the examination of the grain structure and twinned regions by using optical and scanning electron microscopes. The volume fraction of recrystallized grains is determined by image analysis and supported by the hardness measurements.

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Masaki, Kunitaka, Yutaka S. Sato, Masakatsu Maeda, and Hiroyuki Kokawa. "Experimental Estimation of Strain Rate during FSW of Al-Alloy Using Plane-Strain Compression." Materials Science Forum 580-582 (June 2008): 299–302. http://dx.doi.org/10.4028/www.scientific.net/msf.580-582.299.

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Friction stir welding (FSW) makes the stir zone with fine recrystallized grain structure. The recrystallized grains would be formed through dynamic recrystallization at high temperatures and high strain-rate. The present study experimentally simulated the dynamically recrystallized microstructure of a friction stir welded Al alloy 1050 produced at 600 rpm rotation and 100 mm/min travel speed, using combination of the plane-strain compression at various strain rates and the subsequent cooling along the cooling cycle of FSW. The equiaxed grain structures similar to the microstructure of the stir zone were produced at strain rates between 0.1 and 32 s-1; the grain size decreased with increasing strain rate. Strain rate during the FSW could be estimated to be about 1.8 s-1. The present study suggests that plane-strain compression test can simulate the recrystallized grain structure of the friction stir welds.

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Ihara, Kentaro, and Takahiro Shikama. "Effect of Zr Addition on Recrystallization Behavior of Extruded Al-Mg-Si Alloys Containing Mn." Materials Science Forum 794-796 (June 2014): 1169–74. http://dx.doi.org/10.4028/www.scientific.net/msf.794-796.1169.

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Effects of Zr addition on recrystallized structure and texture in extruded Al-Mg-Si alloy containing Mn have been investigated. Materials were homogenized at temperatures in the range 550 °C to 590 °C and extruded at 500 °C at the speed of 10m/min. In extruded Al-Mg-Mn-Si-Zr alloy, the fraction of Cube oriented grains reached 40% as homogenization temperature raised to 590 °C. On the other hand, the fraction of Cube oriented grains in extruded Al-Mg-Mn-Si alloy was limited to 20-30 %. In addition, to clear the formation process of recrystallized grains in these alloys, observation of hot-compression deformed and recrystallized grain structures were carried out. It was suggested that moderate Zener drag promoted the preferential recrystallization of cube oriented grains

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Jun, Joong Hwan, and Min Ha Lee. "Effect of Bi Addition on Thermal Stability and Tensile Ductility of Mg-3%Zn-0.4%Zr Alloy." Materials Science Forum 654-656 (June 2010): 647–50. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.647.

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Thermal stability of  grains and tensile ductilities at room and elevated temperatures were investigated and compared for Mg-3%Zn-0.4%Zr and Mg-3%Zn-0.4%Zr-1%Bi alloys in hot-rolled state. The Bi-added alloy showed slightly finer-grained microstructure with enhanced thermal stability, which is closely associated with fine Mg-Bi compounds acting as obstacles for the migration of grain boundaries. The Mg-3%Zn-0.4%Zr-1%Bi alloy exhibited better tensile strength at room temperature and tensile ductilities at elevated temperature. Finer and more homogeneous grain structure with higher thermal stability would be responsible for the enhanced tensile properties in the Bi-added alloy.

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Journal articles on the topic 'Alloy grain structure'

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