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1
Buha, Joka School of Materials Science & engineering UNSW. "Interrupted ageing of Al-Mg-Si-Cu alloys." Awarded by:University of New South Wales. School of Materials Science and engineering, 2005. http://handle.unsw.edu.au/1959.4/20794.
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This thesis systematically investigates the effects of a recently developed modified ageing procedure of aluminium alloys, termed the T6I6 temper, on the microstructural development and mechanical properties of the Al ??? Mg ??? Si - Cu alloy 6061. For the T6I6 temper, a conventional single stage T6 temper is interrupted by an ageing period at a reduced temperature (65??C) to facilitate secondary precipitation, before resuming the final ageing at the temperature of the initial T6 treatment. The T6I6 temper was found to cause simultaneous increases in tensile properties, hardness, and toughness as compared with 6061 T6. Al ??? Mg ??? Si ??? Cu alloys are medium strength alloys widely used in the automotive industry and their further improvement is underpinned by stringent demands for weight reduction placed on the transportation industry in recent years. The potential for further improvement of the mechanical properties was found in the control of secondary precipitation that may take place even in some fully aged alloys when exposed to reduced temperatures. The overall improvement in the mechanical properties of 6061 T6I6 was attributed to the formation of finer and more densely dispersed precipitates in the final microstructure. The refinement of precipitates was facilitated by control of the precipitation processes and gradual evolution of the microstructure throughout each stage of the T6I6 treatment. The results indicated that the concentration and the chemical environment of the vacancies controlled the precipitation processes in this alloy. Findings also show that the proportion of the different precipitate phases present in the final microstructure, as well as the amount of the solute in these precipitates, can be controlled and modified utilizing secondary precipitation. A number of analytical techniques were used in this study. The evolution of the microstructure was studied using Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM) and Three Dimensional Atom Probe (3DAP). Vacancy-solute interactions were studied using Positron Annihilation Lifetime Spectroscopy (PALS) and 3DAP. The distribution of the solute was studied using 3DAP and Nuclear Magnetic Resonance (NMR). Differential Scanning Calorimetry (DSC) was used to identify precipitation reactions and to determine the stability of vacancy-associated aggregates.
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Zeng, Ruilin. "Precipitation hardening in AZ91 magnesium alloy." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4695/.
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The microstructure evolution of a sand cast AZ91 magnesium alloy during heat treatment (solution treatment and subsequent ageing) were characterized quantitatively using a combination of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The area fraction of discontinuous precipitates and number density of continuous precipitates (N\(_V\)) in the AZ91 alloys with and without pre-deformation were measured using OM and TEM, respectively. Based on these metallurgical evidences, the existing precipitation strengthening mode for AZ91 was modified and the effect of pre-deformation on the precipitation strengthening of AZ91 was investigated. Al-Mn-(Mg) particles in the size range of 20-200 nm have been found in the as-cast AZ91. Their morphologies, chemical composition and structures were investigated using TEM. It was found that these particles have a chemical composition of (Al \(_6\)\(_.\)\(_5\)\(_2\)Mn) \(_1\)\(_-\)\(_x\)Mg\(_x\) (x < 0.13) and a decagonal quasi-crystalline structure. These particles were stable during a solution treatment and acted as preferential nucleation sites for continuous Mg\(_1\)\(_7\)Al\(_1\)\(_2\) precipitates during the subsequent ageing. The results obtained using two electron tomography (ET) approaches were also summarized in this thesis. One uses HAADF-STEM for Mg\(_1\)\(_7\)Al\(_1\)\(_2\) precipitates on Al-Mn-(Mg) particles. The other technique is BF-STEM applied to study Mg\(_1\)\(_7\)Al\(_1\)\(_2\) precipitates on the dislocations.
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Adegoke, Olutayo. "Homogenization of Precipitation Hardening Nickel Based Superalloys." Thesis, Högskolan Dalarna, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:du-11135.
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Allvac 718 Plus and Haynes 282 are relatively new precipitation hardening nickel based superalloys with good high temperature mechanical properties. In addition, the weldability of these superalloys enhances easy fabrication. The combination of high temperature capabilities and superior weldability is unmatched by other precipitation hardening superalloys and linked to the amount of the γ’ hardening precipitates in the materials. Hence, it is these properties that make Allvac 718 Plus and Haynes 282 desirable in the manufacture of hot sections of aero engine components. Studies show that cast products are less weldable than wrought products. Segregation of elements in the cast results in inhomogeneous composition which consequently diminishes weldability. Segregation during solidification of the cast products results in dendritic microstructure with the segregating elements occupying interdendritic regions. These segregating elements are trapped in secondary phases present alongside γ matrix. Studies show that in Allvac 718Plus, the segregating phase is Laves while in Haynes 282 the segregating phase is not yet fully determined. Thus, the present study investigated the effects of homogenization heat treatments in eliminating segregation in cast Allvac 718 Plus and Haynes 282. Paramount to the study was the effect of different homogenization temperatures and dwell time in the removal of the segregating phases. Experimental methods used to both qualify and quantify the segregating phases included SEM, EDX analysis, manual point count and macro Vickers hardness tests. Main results show that there is a reduction in the segregating phases in both materials as homogenization proceeds hence a disappearance of the dendritic structure. In Allvac 718 Plus, plate like structures is observed to be closely associated with the Laves phase at low temperatures and dwell times. In addition, Nb is found to be segregating in the interdendritic areas. The expected trend of increase in Laves as a result of the dissolution of the plate like structures at the initial stage of homogenization is only detectable for few cases. In Haynes 282, white and grey phases are clearly distinguished and Mo is observed to be segregating in interdendritic areas.
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Zangiabadi, Amirali. "Low-temperature interstitial hardening of 15-5 precipitation hardening martensitic stainless steel." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1480769348244855.
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Kubota, Masahiro 1967. "The precipitation hardening response in A1-Mg(-Ag) alloys." Monash University, Dept. of Materials Engineering, 2001. http://arrow.monash.edu.au/hdl/1959.1/9204.
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Ross, T. "Structure and precipitate morphology relationships in a 68Cr-32Ni binary system." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-04212010-143716/.
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Huang, Kai. "Precipitation Strengthening in Al-Ni-Mn Alloys." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-theses/384.
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Precipitation hardening of eutectic and hypoeutectic Al-Ni alloys by 2-4 wt pct. manganese is investigated with focus on the effect of the alloys’ chemical composition and solidification cooling rate on microstructure and tensile strength. Within the context of the investigation, mathematical equations based on the Orowan Looping strengthening mechanism were used to calculate the strengthening increment contributed by each of the phases present in the aged alloy. The calculations agree well with measured values and suggest that the larger part of the alloy’s yield strength is due to the Al3Ni eutectic phase, this is closely followed by contribution from the Al6Mn particles, which precipitate predominantly at grain boundaries
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Gan, Wei. "Precipitation and strengthening in AL-GE-SI alloys." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1135275701.
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Nicol, Alison. "Aspects of copper precipitation and irradiation hardening in Fe-Cu alloys." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325841.
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Gwalani, Bharat. "Developing Precipitation Hardenable High Entropy Alloys." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011755/.
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High entropy alloys (HEAs) is a concept wherein alloys are constructed with five or more elements mixed in equal proportions; these are also known as multi-principle elements (MPEs) or complex concentrated alloys (CCAs). This PhD thesis dissertation presents research conducted to develop precipitation-hardenable high entropy alloys using a much-studied fcc-based equi-atomic quaternary alloy (CoCrFeNi). Minor additions of aluminium make the alloy amenable for precipitating ordered intermetallic phases in an fcc matrix. Aluminum also affects grain growth kinetics and Hall-Petch hardenability.
The use of a combinatorial approach for assessing composition-microstructure-property relationships in high entropy alloys, or more broadly in complex concentrated alloys; using laser deposited compositionally graded AlxCrCuFeNi2 (0 < x < 1.5) complex concentrated alloys as a candidate system. The composition gradient has been achieved from CrCuFeNi2 to Al1.5CrCuFeNi2 over a length of ~25 mm, deposited using the laser engineered net shaping process from a blend of elemental powders. With increasing Al content, there was a gradual change from an fcc-based microstructure (including the ordered L12 phase) to a bcc-based microstructure (including the ordered B2 phase), accompanied with a progressive increase in microhardness. Based on this combinatorial assessment, two promising fcc-based precipitation strengthened systems have been identified; Al0.3CuCrFeNi2 and Al0.3CoCrFeNi, and both compositions were subsequently thermo-mechanically processed via conventional techniques. The phase stability and mechanical properties of these alloys have been investigated and will be presented. Additionally, the activation energy for grain growth as a function of Al content in these complex alloys has also been investigated.
Change in fcc grain growth kinetic was studied as a function of aluminum; the apparent activation energy for grain growth increases by about three times going from Al0.1CoCrFeNi (3% Al (at%)) to Al0.3CoCrFeNi. (7% Al (at%)). Furthermore, Al addition leads to the precipitation of highly refined ordered L12 (γ′) and B2 precipitates in Al0.3CoCrFeNi. A detailed investigation of precipitation of the ordered phases in Al0.3CoCrFeNi and their thermal stability is done using atom probe tomography (APT), transmission electron microscopy (TEM) and Synchrotron X-ray in situ and ex situ analyses.
The alloy strengthened via grain boundary strengthening following the Hall-Petch relationship offers a large increment of strength with small variation in grain size. Tensile strength of the Al0.3CoFeNi is increased by 50% on precipitation fine-scale γ′ precipitates. Furthermore, precipitation of bcc based ordered phase B2 in Al0.3CoCrFeNi can further strengthen the alloy. Fine-tuning the microstructure by thermo-mechanical treatments achieved a wide range of mechanical properties in the same alloy. The Al0.3CoCrFeNi HEA exhibited ultimate tensile strength (UTS) of ~250 MPa and ductility of ~65%; a UTS of ~1100 MPa and ductility of ~30%; and a UTS of 1850 MPa and a ductility of 5% after various thermo-mechanical treatments. Grain sizes, precipitates type and size scales manipulated in the alloy result in different strength ductility combinations. Henceforth, the alloy presents a fertile ground for development by grain boundary strengthening and precipitation strengthening, and offers very high activation energy of grain growth aptly suitable for high-temperature applications.
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Lyon, Mark Edward. "Incorporating Functionally Graded Materials and Precipitation Hardening into Microstructure Sensitive Design." Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd260.pdf.
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Fan, Yangyang. "Precipitation Strengthening of Aluminum by Transition Metal Aluminides." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/231.
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Aluminum-zirconium alloys exhibit superior strength at elevated temperature in comparison to traditional aluminum casting alloys. These alloys are heat-treatable and their strength depends to a large extent on the quenching and aging steps of the heat treatment process. However, measurements show that the critical cooling rate necessary to retain 0.6 wt. pct. zirconium(the minimum amount necessary for significant strengthening) in a super-saturated solid solution with aluminum is 90ºC/s, which is un-attainable with traditional casting processes. On the other hand, the critical cooling rate necessary to retain 0.4 wt. pct vanadium and 0.1 wt. pct. zirconium in a super- saturated solidsolution with aluminum is only 40ºC/s; which suggests that substituting vanadium for zirconium significantly decreases the critical cooling rate of the alloy. This is an important finding as it means that, unlike the Al-0.6Zr alloy, the Al-0.4V-0.1Zr alloy may be processed into useful components by traditional high pressure die-casting. Moreover, measurements show that the hardness of the Al-0.4V-0.1Zr alloy increases upon aging at 400ºC and does not degrade even after holding the alloy at 300ºC for 100 hours. Also, measurements of the tensile yield strength of the Al-0.4V-0.1Zr alloy at 300ºC show that it is about 3 times higher than that of pure aluminum. This increase in hardness and strength is attributed to precipitation of Al3(Zr,V) particles. Examination of these particles with high resolution transmission electron microscopy (HRTEM) and conventional TEM show that vanadium co-precipitates with zirconium and aluminum and forms spherical particles that have the L12 crystal structure. It also shows that the crystallographic misfit between the precipitate particles and the aluminum matrix is almost eliminated by introducing vanadium into the Al3Zr precipitate and thatthe mean radius of the Al3(Zr,V) particles is in the range from 1nm to 7nm depending on the alloy composition and aging practice. Finally, it is found that adding small amounts of silicon to the Al-0.4V-0.1Zr alloy effectively accelerates formation of the Al3(Zr,V) precipitate.
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Liu, Weijie. "Precipitation of Ti(CN) in austenite : experimental results, analysis and modelling." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75434.
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Stress relaxation measurements were carried out on a plain carbon and four Ti steels over the temperature range 850 to 1050$ sp circ$C. The results show that the stress relaxation of plain carbon austenite after a 5% prestrain can be described by the relation $ sigma$ = $ sigma sb0$-$ alpha$ln(1 + $ beta$t). By contrast, in the solution-treated Ti steels, relaxation is arrested at the start of precipitation and is resumed when precipitation is complete. As a result, this new mechanical method is suitable for following carbonitride precipitation in microalloyed austenite at hot working temperatures.PTT diagrams were determined by the present technique for the steels containing 0.05, 0.11, 0.18 and 0.25% Ti. The PTT curves obtained are C shaped for all the steels. The upper parts of these curves are shifted to significantly longer times as the Ti and C concentrations are reduced. By contrast, the positions of the lower arms of the curves are relatively independent of the current values of the solubility product (Ti) (C). This phenomenon is attributed to the catalytic effect of trace amounts of dissolved N on the nucleation rate of Ti(CN) in austenite.
Changes in the size distribution and morphology of the precipitates during relaxation of the 0.25% Ti steel were followed by means of electron microscopy. The cube shaped Ti(CN) precipitates were heterogeneously distributed in either a chain-like or a cell-like manner. Electron microanalysis was additionally carried out to determine the compositions of the Ti carbosulphide-Mn sulphide inclusions.
Finally, the experimental results are compared with the predictions of classical nucleation theory and of the diffusion controlled particle growth theory. Good agreement was obtained between the predictions of the theories and the experimental results. It is demonstrated by means of the thermodynamic analysis of nucleation that the Ti(CN) precipitate/austenite interface is of a semi-coherent nature. It is shown that the interface between a critical nucleus and the matrix can be characterized by the newly introduced coherency loss parameter C.
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Jeniski, Richard A. Jr. "Recrystallization behavior of aluminum alloy 6013." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19412.
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Hwang, Junyeon Kaufman M. J. "Characterization and mechanical properties of nanoscale precipitates in modified Al-Si-Cu alloys using transmission electron microscopy and 3D atom probe tomography." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3661.
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Shahbazian, Yassar Reza. "Characterization and modeling of dislocation-precipitation interactions in aluminum al[l]oys." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Fall2005/r%5Fshahbazian%5Fyassar%5F102305.pdf.
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Negm, N. Z. "Soft X-ray investigations of Pt-Au alloys and precipitation hardening Al based alloys." Thesis, University of Strathclyde, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381737.
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Fan, Yangyang. "Precipitation Strengthening of Aluminum by Transition Metal Aluminides." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/209.
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A castable alloy, i.e., one that flows easily to fill the entire mold cavity and also has resistance to hot tearing during solidification, must invariably contain a sufficient amount of a eutectic structure. For this reason, most traditional aluminum casting alloys contain silicon because the aluminum-silicon eutectic imparts to the alloy excellent casting characteristics. However, the solidus temperature in the Al-Si system does not exceed 577°C, and the major alloying elements (i.e., zinc, magnesium, and copper) used with silicon in these alloys further lower the solidus temperature. Also, these elements have high diffusivity in aluminum and so, while they enhance the room temperature strength of the alloy, they are not useful at elevated temperatures. Considering nickel-base super alloys, whose mechanical properties are retained up to temperatures that approach 75% of their melting point, it is conceivable that castable aluminum alloys can be developed on the same basis so that they are useful at temperatures approaching 350 °C. A castable aluminum alloy intended for high temperature applications must contain a eutectic structure that is stable at temperatures higher than 600°C, and must contain second phase precipitate particles that are thermodynamically stable at the service temperature. Transition metal trialuminides with the general chemical formula AlxTMy in which TM is a transition metal, are excellent candidates for both the eutectic structure and the precipitate particles. In this research, the use of transition metals in the constitution of aluminum casting alloys is investigated with emphasis on the morphology, crystallography, and mechanisms of formation of the various phases.
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Rodgers, Benjamin. "The application of taper-rolling to the near-net-shape production of aluminium wing skins." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/the-application-of-taperrolling-to-the-nearnetshape-production-of-aluminium-wing-skins(8f830ecc-3857-423a-8c44-4f8d78d65b6f).html.
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Initial investigations were conducted to determine the feasibility of applying a post solution heat treatment stress relief stretching operation to near-net-shaped taper rolled aerospace aluminium plate, in terms of the possible process window and the impact on key mechanical properties. Finite element modelling (FEM) and simulations, validated using digital image correlation to measure the strain distribution in flat tapered tensile specimens, have demonstrated the existence of a suitable process window for the production of near-net-shape wing skin blanks. It was revealed that the limits of the available taper geometry are dictated by the work hardening behaviour of the specific aluminium alloy. In addition, in the case of two typical upper wing skin alloys AA2195 and AA7055, tensile and toughness testing revealed that the resultant strain gradient offers the potential for graded mechanical properties suited to this application, with a higher level of toughness at the wing root and an increase in the yield strength of the material at the wing tip. Further, investigations explore the effect of increased tensile pre-stretching, to the maximum achievable before tensile instability, on the strength, microstructure, and precipitation kinetics seen during ageing alloys AA2195 and AA7055. Subsequently, in both alloys, microstructure data have been used to deconvolute and model the effects of increasing pre-strain on the main strengthening components that contribute to the T8 yield strength of the material. In the case of the AA2195 alloy, the T8 yield strength was observed to increase continually as a function of pre-strain to a maximum value of ~670MPa at 15%. It was shown that refinement of the T1 phase continued to the maximum obtainable pre-strain, which was predicted to result in a reduction in the precipitate strengthening contribution. The increase in the T8 yield strength resulting from high levels of pre-strain was attributed to a large increase in residual strain hardening following artificial ageing, owing to a low level of recovery. In the AA7055 alloy, increased pre-strain led to a substantial increase in the T3 yield strength, which was revealed to be due to the dynamic precipitation of GP-Zones. In the T8 temper the yield strength of the alloy increased continually as a function of pre-strain to a maximum of ~607MPa at 24%. Increasing pre-strain was shown to result in a continual and significant increase in the residual strain hardening contribution to the alloys T8 yield strength, due to the occurrence of limited recovery. However, it was also shown that increasing pre-strain led to a progressive reduction in the precipitate strengthening contribution from the eta prime phase, due to an increase in the volume fraction of precipitate free zones (PFZs) with increased dislocation density. Therefore, the increase in the T8 yield strength, as a function of pre-strain, is attributed to an increased residual strain hardening contribution which outweighs a smaller progressive reduction in the precipitate strengthening contribution.
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Martinsen, Fredrik Aleksander. "Clustering during Natural Aging and its Effect on Precipitation Hardening in Al-Mg-Si Alloys." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13636.
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The effect of clustering during natural aging of three different Al-Mg-Sialloys with equal Mg/Si-ratios, but different Mg+Si contents have beenstudied through hardness measurements and transmission electron mi-croscopy (TEM). Hardness measurements were performed both duringnatural aging (NA) and after various NA times followed by subsequentartificial aging for all alloys, while TEM-investigations were performedon selected samples. The results from the experiments were comparedand the existence of three different clustering processes were discovered.The first process was established to be Si-Si clustering causing a slighthardness increase during natural aging and a strong hardness increaseafter subsequent artificial aging. The second process was found to beMg-Mg clustering causing a significant hardness increase during naturalaging, and a clear decrease in hardness after subsequent artificial aging.The third process was found to be Mg-Si clustering and simultaneoustransformation of mono-clusters into co-clusters. This combined processcauses a hardness increase both during natural aging and after subse-quent artificial aging. The hardness increase is caused by a refinementof alloy microstructure including a higher number of smaller ” needles.This precipitate type was observed for all alloys and conditions. Thenegative effect of Mg-Mg clusters on precipitation hardness is suggestedto be related to the repulsion of Si from these clusters. This hinders theco-clustering of Mg and Si in the areas surrounding these clusters.
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Leitch, John Edward. "The role of interstitial nitrogen in the precipitation hardening reactions in high-chromium ferritic steels." Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/22176.
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Bibliography: pages 107-108.The effects of exposure to temperatures in the range 475 - 800°C on the hardness and associated microstructure of high chromium ferritic steels has been investigated. Low-carbon 26Cr-1Mo steels containing 0,02 - 0,04% nitrogen were found to constitute an age hardening system when quenched from a temperature of nitrogen solubility and exposed at temperatures in the range 600 - 700°C. TEM observations on thin foils revealed that hardening was associated with the formation of a high density of Cr-N zones. These grew on over-ageing into disc-shaped Cr-N precipitates situated on {100} lattice planes, and ultimately became large incoherent precipitates. Ageing at 475°C and 550°C produced hardening due to the formation of chromium-rich ferrite phases α' as a result of the miscibility gap in the Fe-Cr phase diagram. However the presence of interstitial nitrogen in solution in the steel considerably reduced the rate of hardening, especially at 475°C. TEM examination confirmed that this effect was due to the formation of Cr-N zones in preference to α'. This type of decomposition occurs by a mechanism of nucleation and growth, forming zones similar to those formed during an ageing at 600°C. When depleted of interstitial nitrogen, through precipitation at 800°C or through zone formation at 475°C, the specimens aged at 475°C underwent spinodal decomposition. Thus nitrogen in solid solution was found to have a significant effect on the 475°C hardening reaction. Precision X-ray diffraction measurements revealed the presence of secondary diffraction peaks associated with the Bragg peaks, which comfirmed the formation of Cr-rich phases during ageing at 475°C. The calculated associated lattice parameter measurements allowed estimates of the compositions of the decomposition phases to be made. These were calculated to be about 6-18% Cr in the Fe-rich and 60-80% Cr in the Cr-rich phases of the 26Cr-1Mo steel.
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Mattes, Victor R. "Microstructure and mechanical properties of HSLA-100 steel." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA242937.
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Thesis (M.S. in Mechanical Engineering and Mechanical Engineer)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Fox, Alan G. "December 1990." Description based on title screen as viewed on April 2. 2010. DTIC Identifier(s): Steel, Microstructure, Mechanical Properties, Copper, Quenching, Tempering, Processing, Naval Vessels, HSLA-100 Steel, Theses, Age Hardening, Modulus of Elasticity, Charpy V Notch Tests. Author(s) subject terms: HSLA-100, Mechanical Properties, Copper Precipitation, Carbide. Includes bibliographical references (p. 66-68). Also available in print.
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Rey, Tomas. "Investigation of Microstructure and Mechanical Properties in Hot-work Tool Steels." Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210699.
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Hot-work tool steels make up an important group of steels that are able to perform with good strength and toughness properties at elevated temperatures and stresses. They are able to gain this behavior through their alloy composition and heat treatment, which relies on the precipitation of alloy carbides to counter the loss in strength as the tempered material becomes more ductile. As demand grows for materials that are suitable for even harsher applications and that show improved mechanical qualities, the steel industry must continuously investigate the development of new steel grades. Within this context, the present work focuses on examining the mechanical properties and microstructure of two hot-work tool steels, of which one is a representative steel grade (Steel A) and the second a higher-alloyed variant (Steel B), at different tempering conditions. To complement the experimental work, precipitation simulations are used to monitor the progression of secondary carbide precipitation and to examine the predicted microstructural changes through varying the alloy composition. The study finds that Steel B does not actually have improved properties with respect to Steel A and suggests that the precipitation behavior of both steels is virtually identical. Despite this, the simulation work reveals that this behavior can change dramatically to favor more positive hardness contributions by increasing the alloy content of V. In short, with the project being part of an ongoing investigation, there remain several areas of analysis that need to be completed before offering a complete picture that can ultimately play a part in the development of a new hot-work tool steel grade.
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PRASAD, PRASHANTH. "CHARACTERIZATION OF NEW, CAST, HIGH TEMPERATURE ALUMINUM ALLOYS FOR DIESEL ENGINE APPLICATIONS." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1148315194.
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Reimann, Martin [Verfasser], and Norbert [Akademischer Betreuer] Huber. "Keyhole repair in precipitation hardening aluminum alloys using refill friction stir spot welding / Martin Reimann ; Betreuer: Norbert Huber." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2018. http://d-nb.info/1172812853/34.
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Winkelman, Graham B. "Precipitation at dislocations in Al-Cu-Mg alloys." Monash University, School of Physics and Materials Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9581.
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Hwang, Junyeon. "Characterization and Mechanical Properties of Nanoscale Precipitates in Modified Al-Si-Cu Alloys Using Transmission Electron Microscopy and 3D Atom Probe Tomography." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc3661/.
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Among the commercial aluminum alloys, aluminum 319 (Al-7wt%Si-4wt%Cu) type alloys are popularly used in automobile engine parts. These alloys have good casting characteristics and excellent mechanical properties resulting from a suitable heat treatment. To get a high strength in the 319 type alloys, grain refining, reducing the porosity, solid solution hardening, and precipitation hardening are preferred. All experimental variables such as solidification condition, composition, and heat treatment are influence on the precipitation behavior; however, precipitation hardening is the most significant because excess alloying elements from supersaturated solid solution form fine particles which act as obstacles to dislocation movement. The challenges of the 319 type alloys arise due to small size of precipitate and complex aging response caused by multi components. It is important to determine the chemical composition, crystal structure, and orientation relationship as well as precipitate morphology in order to understand the precipitation behavior and strengthening mechanism. In this study, the mechanical properties and microstructure were investigated using transmission electron microscopy and three dimensional atom probe tomography. The Mn and Mg effects on the microstructure and mechanical properties are discussed with crystallographic study on the iron intermetallic phases. The microstructural evolution and nucleation study on the precipitates in the low-Si 319 type aluminum alloys are also presented with sample preparation and analysis condition of TEM and 3DAP tomography.
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Zander, Johan. "Modelling mechanical properties by analysing datasets of commercial alloys." Licentiate thesis, Stockholm : Industriell teknik och management, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4527.
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Letovanec, Juraj. "Vliv teplotního režimu vytvrzování slitin typu Al-Si na mechanické vlastnosti." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-387729.
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The aim of this thesis is influence of precipitation hardening regime, specifically quench rate, on mechanical properties of aluminium alloy A356 (AlSi7Mg0.3). Samples were after solution treatment quenched into water with different temperatures and age hardened. Tensile strength tests, hardness tests and microstructure observations were done after heat tretment.
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Tanprayoon, Dhritti [Verfasser]. "Investigation of the precipitation hardening behaviour and the corrosion properties of novel aluminium : manganese alloys containing scandium and zirconium / Dhritti Tanprayoon." Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2015. http://d-nb.info/1079106235/34.
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Apps, Peter Joseph. "The effects of the rare earth elements yttrium, gadolinium and dysprosium on the microstructure and properties of precipitation hardening magnesium alloys." Thesis, University of Manchester, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488095.
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PADIAL, ARMANDO G. F. "Caracterizacao microestrutural do aco maraging de grau 400 de resistencia mecanica ultra-elevada." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10998.
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Made available in DSpace on 2014-10-09T12:46:42Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:56:09Z (GMT). No. of bitstreams: 1 07613.pdf: 5555459 bytes, checksum: 0047c9f052248797761d648268e841ba (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Meher, Subhashish. "Comparative Coarsening Kinetics of Gamma Prime Precipitates in Nickel and Cobalt Base Superalloys." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699871/.
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The increasing technological need to push service conditions of structural materials to higher temperatures has motivated the development of several alloy systems. Among them, superalloys are an excellent candidate for high temperature applications because of their ability to form coherent ordered precipitates, which enable the retention of high strength close to their melting temperature. The accelerated kinetics of solute diffusion, with or without an added component of mechanical stress, leads to coarsening of the precipitates, and results in microstructural degradation, limiting the durability of the materials. Hence, the coarsening of precipitates has been a classical research problem for these alloys in service. The prolonged hunt for an alternative of nickel base superalloys with superior traits has gained hope after the recent discovery of Co-Al-W based alloys, which readily form high temperature g precipitates, similar to Ni base superalloys. In the present study, coarsening behavior of g precipitates in Co-10Al-10W (at. %) has been carried out at 800°C and 900°C. This study has, for the first time, obtained critical coarsening parameters in cobalt-base alloys. Apart from this, it has incorporated atomic scale compositional information across the g/g interfaces into classical Cahn-Hilliard model for a better model of coarsening kinetics. The coarsening study of g precipitates in Ni-14Al-7 Cr (at. %) has shown the importance of temporal evolution of the compositional width of the g/g interfaces to the coarsening kinetics of g precipitates. This study has introduced a novel, reproducible characterization method of crystallographic study of ordered phase by coupling of orientation microscopy with atom probe tomography (APT). Along with the detailed analysis of field evaporation behaviors of Ni and Co superalloys in APT, the present study determines the site occupancy of various solutes within ordered g precipitates in both Ni and Co superalloys. This study has explained the role of structural and compositional gradients across the precipitates (g)/matrix (g) interfaces on the coarsening behavior of coherent precipitates in both Ni and Co-base superalloys. The observation of two interfacial widths, one corresponding to a structural order-disorder transition, and the other to the compositional transition across the interface, raises fundamental questions regarding the definition of the interfacial width in such systems. The comparative interface analysis in Co and Ni superalloy shows significant differences, which gives insights to the coarsening behaviors of g precipitates in these alloys. Hence, the principal goal of this work is to compare and contrast the Co and Ni superalloys and also, to accommodate atomic scale information related to transitions across interfaces to coarsening models for a better practical applicability of coarsening laws to various alloys.
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Zahiri, Saden H. (Saden Heshmatollah) 1966. "Prediction of the processing window and austemperability for austempered ductile iron." Monash University, School of Physics and Materials Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/8408.
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Fan, Yangyang. "Alloying Aluminum with Transition Metals." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/266.
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A castable alloy, i.e., one that flows easily to fill the entire mold cavity and also has resistance to hot tearing during solidification, must invariably contain a sufficient amount of a eutectic structure. For this reason, most traditional aluminum casting alloys contain silicon because the aluminum-silicon eutectic imparts to the alloy excellent casting characteristics. However, the solidus temperature in the Al-Si system does not exceed 577°C, and the major alloying elements (i.e., zinc, magnesium, and copper) used with silicon in these alloys further lower the solidus temperature. Also, these elements have high diffusivity in aluminum and so, while they enhance the room temperature strength of the alloy, they are not useful at elevated temperatures. Considering nickel-base super alloys, whose mechanical properties are retained up to temperatures that approach 75% of their melting point, it is conceivable that castable aluminum alloys can be developed on the same basis so that they are useful at temperatures approaching 350C. A castable aluminum alloy intended for high temperature applications must contain a eutectic structure that is stable at temperatures higher than 600°C, and must contain second phase precipitate particles that are thermodynamically stable at the service temperature. Transition metal trialuminides with the general chemical formula AlxTMy in which TM is a transition metal, are excellent candidates for both the eutectic structure and the precipitate particles. In this research, the use of transition metals in the constitution of aluminum casting alloys is investigated with emphasis on the morphology, crystallography, and mechanisms of formation of the various phases.
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Tang, Fei. "The Microstructure-Processing-Property Relationships in an Al Matrix Composite System Reinforced by Al-Cu-Fe Alloy Particles." Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/835313-syGDu9/webviewable/.
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Grosset, Lisa. "Développement et validation d’un modèle de vieillissement thermique d’alliages d’aluminium pour application aéronautique." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEM010.
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Les exigences des clients du secteur aéronautique imposent aux entreprises de prendre en compte pour le dimensionnement les effets de la température sur toute la durée de vie du produit. Cependant, aucune loi ne permet actuellement de prévoir l’impact du vieillissement thermique sur le comportement des matériaux. Ce travail a pour objectif de comprendre le mécanisme de vieillissement thermique des alliages d’aluminium et son impact sur les propriétés mécaniques, mais surtout d’acquérir un outil performant capable d’obtenir rapidement des données matériaux après vieillissement.Au cours de cette étude, de nombreuses analyses microstructurales et mécaniques ont été réalisées sur trois alliages d’aluminium à durcissement structural. Différentes combinaisons temps-température de vieillissement ont été testées afin de disposer d’une large base de données sur ces matériaux (caractéristiques mécaniques statiques Rm, Rp0,2 et dureté et tailles des précipités durcissants). Ces données ont ensuite été compilées dans un modèle de vieillissement basé sur les théories classiques de durcissement structural, de croissance et de coalescence des précipités.Le modèle de vieillissement créé répond au besoin initial et prédit de façon conservative le comportement mécanique des alliages ayant subi un vieillissement thermique isotherme. Des axes d’amélioration sont envisagés pour ce modèle évolutif, comme l’intégration de la prévision du comportement en fatigue ainsi que le traitement de cas anisothermes pour une représentation plus réelle des conditions de service des pièces aéronautiquesIn aeronautics, customers ask companies to consider the effects of temperature over the entire life of the product in structural requirements. Indeed, aircraft parts are demanded to last longer (up to 90 000 hours) and operate at higher temperatures (up to 250°C). No laws enable to predict the impact of thermal ageing on materials behavior. Current practices are to perform mechanical testing after ageing in ovens at various temperatures, but they are expensive and incompatible with the development schedules. This work aims to understand the thermal aging mechanism of aluminum alloys and its impact on mechanical properties, but especially to acquire a powerful tool able to quickly obtain material data after aging.During this study, many microstructural and mechanical analyses were conducted on three precipitation hardened aluminum alloys. Different combinations of aging time and temperature were tested to get a large database of these materials (static mechanical characteristics Rm, Rp0,2 and hardness and sizes of hardening precipitates). These data were then compiled into a computing aging model based on the classical theories of precipitation hardening, growth and coarsening of precipitates.The created aging model responds to the initial need and can conservatively predict the mechanical behavior of aluminum alloys under isothermal aging. Improvement areas are considered for this evolutionary model, such as the integration of fatigue behavior prediction and the inclusion of thermal cycles for a more realistic representation of service conditions of aircraft parts
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Lindwall, Greta. "Multicomponent diffusional reactions in tool steels : Experiment and Theory." Doctoral thesis, KTH, Termodynamisk modellering, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103328.
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Many phenomena determining the microstructure of a tool steel and consequently the properties of the material, are governed by multicomponent diffusion. The diffusion driven reactions that take place during, for example, tempering of a hot-work tool steel or when the microstructure develops during hot isostatic pressing of cold-work tool steel, are dependent on the types and amounts of alloying elements. In order for computational methods to be usable, these alloying effects need to be understood and incorporated in the models. In this work the influence of some typical tool steel alloying elements on the coarsening behavior of precipitates is investigated. Experimental coarsening studies are performed and the impact of the diffusion mobility descriptions and the thermodynamic descriptions are investigated by means of DICTRA coarsening calculations. The kinetic descriptions for diffusion in the body centered-cubic phase in the case of the chromium-iron-vanadium system and the chromium-iron-molybdenum system are improved by assessments of diffusion mobility parameters, and are shown to have a large impact on the calculated coarsening rate for vanadium-rich and molybdenum-rich precipitates. The effect of cobalt is examined by a coarsening experiment for vanandiumrich carbides and by a diffusion couple experiment for the investigation of the vanadium interdiffusion. The presence of cobalt is experimentally shown to have retarding effect on the coarsening rate of the carbides, but not on the vanadium diffusion. The coarsening rate of nitrogen-rich precipitates is compared to the coarsening rate of carbon-rich precipitates, and a lower coarsening rate for nitrides compared to carbides can be confirmed. Correlation between coarsening calculations and experiments is obtained suggesting that the thermodynamic description of the two systems is the underlaying reason for the different coarsening rates. Further, calculations utilizing the DICTRA software are combined with experimental investigations in order to study the possibility to apply computational methods for compound material development and explore application areas for high nitrogen alloyed tool steels produced by powder metallurgy.QC 20121011
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Lv, Duchao. "A Multi-Scale Simulation Approach to Deformation Mechanism Prediction in Superalloys." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469009668.
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Tintillier, Rémy. "Résistance à la propagation aux faibles vitesses des fissures de fatigue dans un alliage aluminium-lithium type 8090." Poitiers, 1988. http://www.theses.fr/1988POIT2295.
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Caracterisation du comportement en fissuration par fatigue au voisinage du seuil de non-propagation dans l'alliage al-2,5li-1,4cu-0,7 mg dans trois conditions de revenu, soumis a des essais de seuil sous vide et a l'air pour des rapports de charge variant de 0,01 a 0,8. Comparaison avec des alliages d'aluminium conventionnels. Determination a partir de cette comparaison du mecanisme de glissement planaire induit par la precipitation durcissante delta ' dans l'alliage 8090. Analyse des differences de comportement en tenant compte des effets de fermeture et des interactions microstructure-environnement. Etude du comportement en fatigue des alliages binaires al-li de haute purete mono et polycristallins
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Ibrahim, Alaaeldin Mahmoud Hussien [Verfasser], Reinhard [Gutachter] Krause-Rehberg, Hartmut S. [Gutachter] Leipner, and John [Gutachter] Banhart. "The role of trace elements on formation of quenched-in vacancies and precipitation hardening in Al-alloys / Alaaeldin Mahmoud Hussien Ibrahim ; Gutachter: Reinhard Krause-Rehberg, Hartmut S. Leipner, John Banhart." Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2019. http://d-nb.info/121072734X/34.
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Ibrahim, Alaaeldin Mahmoud Hussien [Verfasser], Reinhard Gutachter] Krause-Rehberg, Hartmut S. [Gutachter] Leipner, and John [Gutachter] [Banhart. "The role of trace elements on formation of quenched-in vacancies and precipitation hardening in Al-alloys / Alaaeldin Mahmoud Hussien Ibrahim ; Gutachter: Reinhard Krause-Rehberg, Hartmut S. Leipner, John Banhart." Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2019. http://d-nb.info/121072734X/34.
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Ibrahim, Alaaeldin Mahmoud Hussien [Verfasser], Reinhard Gutachter] Krause-Rehberg, Hartmut S. [Gutachter] [Leipner, and John [Gutachter] Banhart. "The role of trace elements on formation of quenched-in vacancies and precipitation hardening in Al-alloys / Alaaeldin Mahmoud Hussien Ibrahim ; Gutachter: Reinhard Krause-Rehberg, Hartmut S. Leipner, John Banhart." Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2019. http://nbn-resolving.de/urn:nbn:de:gbv:3:4-1981185920-324604.
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Kovarik, Libor. "Microstructural study and modeling of metastable phases and their effect on strenghthening [sic] in Al-Mg-Cu-Si alloying system." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1149006665.
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Phung-on, Isaratat. "An investigation of reheat cracking in the weld heat affected zone of type 347 stainless steel." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1188419315.
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Beraldo, Camila Haga. "Efeito da temperatura de envelhecimento sobre as propriedades mecânicas e resistência à corrosão por pite do aço inoxidável martensítico endurecido por precipitação UNS S46500." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-15102014-163925/.
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Os aços inoxidáveis endurecidos por precipitação vêm sendo largamente empregados na indústria aeronáutica, por combinar resistência mecânica, tenacidade à fratura e resistência à corrosão. E deste modo, são materiais que possibilitam a substituição dos aços carbonos utilizados atualmente, que necessitam de tratamento superficial adicional, como o cádmio, para melhorar a resistência à corrosão. A utilização desses revestimentos traz desvantagens como o custo, a fabricação, a susceptibilidade à fragilização por hidrogênio além dos aspectos ambientais. Neste contexto, o aço endurecido por precipitação UNS S46500, designado como Custom 465® foi avaliado considerando o efeito da temperatura de envelhecimento sobre as propriedades mecânicas e a resistência à corrosão por pite. Amostras tratadas nas condições solubilizada e envelhecida a 510ºC (H950) e 538ºC (H1000) foram submetidas ao ensaio de tração, caracterização microestrutural e ensaios de polarização potenciodinâmica (PP) para determinar a resistência à corrosão por pite. Os exames microestruturais foram realizados com auxílio de microscopia óptica (MO), microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e difração de raios X. Também foram realizadas análises utilizando o software Thermo-Calc. A resistência à corrosão por pite foi avaliada em solução 0,6M NaCl com adições crescentes de Na2SO4. Os resultados obtidos nos ensaios de PP nas duas condições de tratamento térmico foram comparados entre si e com resultados disponíveis na literatura (CALDERÓN-HERNANDEZ, 2012) para o aço inoxidável UNS S30403 (304L). Os exames e análises da microestrutura revelaram que o aço Custom 465® envelhecido apresenta uma matriz martensítica, precipitados de fase chi, austenita e precipitados Ni3Ti. O tratamento H950 apresentou maior resistência mecânica e menor alongamento do que o tratamento H1000. Tal comportamento foi devido à produção de maior porcentagem de fase chi e menor porcentagem de austenita nesse tratamento de envelhecimento. Os diferentes tratamentos térmicos, condição solubilizada, H950 e H1000 apresentaram praticamente a mesma resistência à corrosão por pite. Por outro lado, o aço Custom 465® apresentou ótima resposta à inibição da nucleação de pite com adições crescentes de sulfato em meio de 0,6M NaCl, sendo que a condição H1000 se sobressai sobre a H950 nessa questão. Além disso, através da adição de sulfato foi 7 possível obter maior resistência a corrosão por pite do aço Custom 465® comparativamente ao aço 304L. Tal comportamento foi discutido em termos da afinidade química entre níquel, cloreto e sulfato, levando a maior resistência à corrosão por pite quando o aço contém maior teor de níquel (que é o caso do aço Custom 465®). Este trabalho indicou que o critério na escolha do tratamento de envelhecimento do aço Custom 465® deve ser o das propriedades mecânicas almejadas, uma vez que a resistência à corrosão por pite mostrou-se praticamente independente do tratamento térmico.The precipitation hardened stainless steels have been widely used in the aircraft industry to combine mechanical strength, fracture toughness and corrosion resistance. And therefore, are materials that enable replacement of the carbon steels used today, which require additional surface treatment, such as cadmium plating, to improve the corrosion resistance. The use of such coatings brings disadvantages such as cost, manufacturing, susceptibility to hydrogen embrittlement beyond environmental aspects. In this context, the precipitation hardened steel UNS S46500, known as Custom 465® were evaluated for the effect of aging temperature on the mechanical properties and the resistance to pitting corrosion .Treated samples in solubilized and aged condition at 510°C (H950) and 538ºC (H1000) were subjected to tensile strength test, microstructural characterization and potentiodynamic polarization (PP) tests to determine the pitting corrosion resistance. The microstructural studies were performed with the aid of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction. Analyzes were also performed using the Thermo -Calc software. The resistance to pitting corrosion was evaluated at 0.6M NaCl solution with increasing additions of Na2SO4. The results obtained from tests of PP in both heat treatment conditions were compared with each other and with results available in the literature (CALDERÓN HERNANDEZ, 2012) to stainless steel UNS S30403 (304L). The analysis of the microstructure revealed that the steel aged Custom 465 ® presents a martensitic matrix, chi precipitates, Ni3Ti precipitates and austenite phase. The H950 age treatment had higher mechanical strength and lower elongation than the treatment H1000. Such behavior was due to the production of higher percentage of chi and a lower percentage of austenite phase in aging treatment. The different heat treatments, solubilized condition, H950 and H1000 showed almost the same pitting corrosion resistance. On the other hand, the Custom 465® showed good response to pitting inhibition with increasing nucleating additions of sulfate in 0.6M NaCl, with enhanced result for H1000 condition. Furthermore, by adding sulfate was possible to obtain greater pitting corrosion resistance of Custom 465® compared to the 304L steel. This behavior has been discussed in terms of the chemical affinity between nickel, chloride and sulphate, leading to higher pitting corrosion resistance when the steel contains a higher nickel 9 content (which is the case of steel Custom 465®). This study indicates that the criterion in selecting the aging heat treatment of Custom 465® steel must be the desired mechanical properties, since the pitting corrosion resistance was found to be substantially independent of heat treatment.
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Perrier, Malika. "Etude de la relation entre la microstructure et les propriétés mécaniques d'un acier durci par précipitation intermétallique intense : le Fer-Silicium-Titane." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00721729.
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L'amélioration des propriétés mécaniques dans les alliages du système Fer-Silicium-Titane grâce à l'introduction d'une précipitation nanométrique a été démontrée dans la littérature. La haute valeur de limite d'élasticité qui peut être atteinte dans ces aciers en fait de bons candidats pour des applications dans l'élaboration de structures automobiles. Dans ce contexte, cette étude a pour objectif de caractériser et comprendre la séquence et la cinétique de précipitation dans ces alliages, ainsi que les relations entre microstructure de précipitation et propriétés mécaniques, dans une démarche de conception d'alliages optimisée. La démarche utilisée a tout d'abord consisté en une caractérisation multi-échelle de la précipitation par diffusion des neutrons aux petits angles, microscopie électronique en transmission et sonde atomique tomographique, qui a permis d'aboutir à une description précise de la structure, composition, taille et fraction volumique des précipités, qui ont ensuite été reproduites par modélisation. Dans un deuxième temps, les tests mécaniques réalisés à température ambiante ont révélé un fort potentiel durcissant, qui dépend du temps et de la température de vieillissement. Des modèles à base physique pour la limite d'élasticité et le taux d'écrouissage (tenant compte des contributions isotropes et cinématiques) ont été appliqués pour décrire les courbes de traction mesurées. Ceux-ci ont permis d'aboutir à une bonne compréhension des relations entre microstructures et propriétés dans le système Fe-Si-Ti.
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Balan, Alexandre. "Modélisation isotherme et anisotherme de la limite d'élasticité précipitation-dépendante de l'Inconel 718." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI003/document.
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Ce manuscrit de thèse présente les résultats de travaux concernant les effets des transitoires thermiques sur la précipitation des phases intermétalliques dans le superalliage base nickel Inconel 718® et les conséquences de cette précipitation sur les propriétés mécaniques de cet alliage. Ces travaux se concentrent sur une approche couplée capable de décrire l’évolution de la précipitation de la phase γ'' et ses conséquences sur la limite d’élasticité de l’Inconel 718®. L’état de précipitation est modélisé grâce à l’implémentation des équations de la théorie classique de germination et de croissance, modifiées afin de prendre en compte la géométrie en plaquette des précipités γ''. Ce modèle de précipitation est ensuite validé par des données expérimentales issues de la littérature mais également d’observations au microscope électronique en transmission et d’essais de diffusion de neutrons aux petits angles. La distribution de taille de la phase γ'' ainsi simulée est utilisée comme donnée d’entrée d’un modèle de prédiction de la limite d’élasticité précipitation-dépendant. Ces limites d’élasticité simulées sont enfin comparées à des résultats expérimentaux issus d’essais de traction. Une maquette de soudage a ensuite été réalisée afin de tester le modèle de prévision de limite d’élasticité pour des transitoires thermiques, dans un cas industrielThis thesis manuscript presents the results of work concerning the effects of thermal transients on the precipitation of intermetallic phases in the nickel-based superalloy Inconel 718® and the consequences of this precipitation on the mechanical properties of this alloy. This work focuses on a coupled approach capable of describing the evolution of the precipitation of the γ'' phase and its consequences on the yield strength of the Inconel 718®. The precipitation state is modeled thanks to the implementation of the equations of the classical germination and growth theory, modified to take into account the platelet geometry of the γ'' precipitates. This precipitation model is then validated by experimental data from the literature but also from transmission electron microscope observations and small angle neutron scattering tests. The size distribution of the γ'' phase thus simulated is used as the input data of a model for predicting the precipitation-dependent elasticity limit. These simulated elasticity limits are finally compared with experimental results from tensile tests. A welding model was then made to test the elastic yield prediction model for thermal transients in an industrial case
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Ševčíková, Barbora. "Koroze neželezných kovových materiálů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2018. http://www.nusl.cz/ntk/nusl-390295.
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In the presented dissertation thesis, I closely focused on corrosion resistance of non-ferrous metals. For full understanding of the possibilities for increasing corrosion resistance, it was vital to initially recognize the influences to the corrosion system of the samples and their surrounding environment. For this purpose, I focused on heat treatment, corrosion, and protective coatings, in the theoretical part of the thesis. For the subsequent research, it was necessary to define several constant variables, first. For this purpose, I have chosen a group of magnesium alloys, namely AZ91 Alloy and 3.5 % NaCl Electrolyte. AZ91 Alloy is of heterogenous structure formed by a solid solution of aluminum in magnesium, intermetallic phase in Mg17Al12, and their eutectic. Local microcells tend to occur in these heterogenities, which leads to faster corrosion. In order to increase corrosion resistance of the alloy, I used a combination of heat treatment and protective phosphate coating. For creating of the desired structure, which further affects compact coating formation, I selected a process involving solution heating with precipitation hardening T6. Secondary goals of the thesis involved optimization of standard technical procedures for the sake of increasing efficiency. With regard to this goal, I introduced optimized heat treatment T6 using accelerated cooling of a sample in water and liquid nitrogen. A modification besides the standard phosphating procedure was carried out with no activation step. For evaluation of corrosion resistance of the samples, I conducted water immersion tests using electrochemical methods; such as potenciodynamic curves combined with electrochemical impedance spectroscopy. In order to streamline the evaluation of the corrosion surface in technical practice, I used automatic detection. Substantial improvement of corrosion resistance of the above mentioned system, compared to heat-untreated samples, was proven through electrochemical methods. Due to accelerated cooling, a more homogeneous structure was achieved, which could be further utilized to create more uniform protective coating. For some phosphate coating, specifically manganese phosphate coating, I identified certain modifications that were in line with the set goals; i.e. skipping the activation phase, and using automatic detection for evaluation of uniform corrosion on the samples.
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Jubica, Jubica. "Characterization of Secondary Carbides in Low-Alloyed Martensitic Model Alloy Tool Steels." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284449.
Full textAbstract:
The development of tool steels for making and shaping other materials requires a better understanding of the material's properties during manufacture. These high-quality steels include many alloying elements, which give increased hardness during tempering. For producing hardened microstructures, austenite generation is essential. The martensite formed by rapid quenching of austenite followed by tempering helps develop high strength steels. Studying carbide precipitation is a challenge as they are very small in size, present only in small volume fractions and high number densities. The carbide reactions are complicated due to so-called metastable carbides, which are only present as part of the precipitation process. This work focuses on model alloys with two main elements in addition to iron and carbon, molybdenum, and vanadium, to clarify and simplify the carbide characterization. This is done to determine the effect of molybdenum and vanadium carbides on the overall hardness. In this work, two model alloys, A and B, are tempered at 550°C and 600°C with the same vanadium content but different molybdenum contents. The hardness of the materials is evaluated and compared at these temperatures. A more detailed characterization work is done for material A with Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy (STEM-EDS) to understand the microstructure and analyze the precipitates. Simulations are performed with Thermo-Calc Prisma (TC-Prisma) to support the experimental work, which includes the simulation of the secondary carbide precipitation, mainly molybdenum carbides in material A tempered for 24h at 600°C, and predicts the carbide precipitation behavior in this steel. The results from STEM-EDS and TC-Prisma for material A, show that the small secondary carbides in the martensite contribute to the increased strength of material A. Due to the overaging of the carbides at 600°C, the hardness at 550°C is higher than at 600°C for material A. The given thesis work is an attempt to interpret the development of secondary carbides of Mo and V in the martensitic matrix and their role in the overall hardness.Den ständiga utvecklingen av högpresterande stål för transport, konstruktion och energisektorn kräver bättre förståelse för materialets egenskaper vid tillverkning. Dessa martensitiska stål inkluderar många legeringselement vilket ger ökad hårdhet vid härdning och anlöpning. Att studera utskiljning av karbider är en utmaning eftersom de är närvarande endast i liten volymsfraktion. Karbidreaktionerna är komplexa till följd av så kallade metastabila karbider vilka endast är närvarande vid en del av utskiljningsförloppet. För att tydliggöra och förenkla karbidkarakteriseringen fokuserar detta arbete på modellegeringar med två huvudelement utöver järn och kol, molybden och vanadin. Detta görs för att fastställa effekten av molybden och vanadinkarbider på den totala hårdheten. I detta arbete studeras två modellegeringar, A och B, härdade och anlöpta vid 550 °C och 600 °C med samma vanadininnehåll men olika molybdeninnehåll. Materialens hårdhet utvärderas och jämförs vid dessa temperaturer. Ett mer detaljerat karaktäriseringsarbete görs för material A med hjälp av STEM-EDS för att förstå mikrostrukturen och analysera utskiljningarna. Simuleringar görs med TC-PRISMA för att stödja det experimentella arbetet, vilket inkluderar simulering av den sekundära karbidutskiljningen och predikterar karbidstrukturen i dessa stål. Resultaten visar att de små sekundärkarbiderna i martensiten bidrar till den ökade styrkan hos material A. Hårdheten vid 550 °C är högre än vid 600 °C för material A eftersom både utskiljningen av karbider är sker långsammare och även dislokationsåterhämtning.