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Anisotropy in dynamic recrystallization behavior of AZ31 magnesium alloy

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Journal of Magnesium and Alloys 2022年第12期10卷 3470-3484页

作者： S.M.Fatemi S.Kheyrabadi H.Paul Department of Metallurgy and Materials Engineering Shahid Rajaee Teacher Training University136-16785 TehranIran Institute of Metallurgy and Materials Science Polish Academy of Sciences(PAS)25 Reymonta Street30-059 KrakowPoland

Deformation behavior as well as microstructural evolutions of a rolled AZ31 magnesium alloy with and without pre-existing extension Twins were studied using compression tests which performed along different orientations at a temperature range of 25–350 ℃. The results implied that the initial texture not only influence the evolution of flow stress, but also change the size and fraction of recrystallized grains.In contrast to samples parallel to rolling and transverse directions, compression along normal direction resulted in a respectful softening at 150 ℃. The largest size and fraction of new grains at 250 ℃ were recorded after deformation along rolling direction, while the maximum flow softening was observed during deformation along normal direction. The anisotropy in microstructural evolutions was still retained at 350 ℃. Pre-existing Twins could reduce the anisotropy of material in respect of flow stress as well as DRX progression, where TD sample showed the lowest DRX fraction at 250 ℃. Quaternion misorientation data obtained from EBSD analysis of preTwinned material implied that initial texture could not significantly influence final texture. A different misorientation distribution was realized after deformation of preTwinned material along ND and RD directions.

关键词： Slip Recrystallization Grain size Growth Twin

Exploring the ultrahigh rolling contact fatigue life of M50 bearing steel by adjusting the cryogenic sequence

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Journal of Materials Science & Technology 2024年第2期169卷 243-250页

作者： Xin Cai Xiaoqiang Hu Xingyu Lu Hongwei Liu Yanfei Cao Dianzhong Li Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

The influence of different cryogenic sequences on the rolling contact fatigue(RCF)life of M50-bearing steel has been studied.The results show that direct cryogenic treatment after quenching can effectively improve RCF life.The L_(10)life is strikingly 5 times longer than that with cryogenic treatment after tem-pering.This is caused by the distinct lattice construction of martensite and the transformation of retained austenite.More secondary nanocarbides and fine Twins are formed via cryogenic treatment before tem-pering compared with cryogenic treatment after tempering.The improvement in the RCF life of the steel is attributed to the joint effects of the secondary nanocarbides and Twin boundaries with a width of 5-13 nm,which delays significantly crack initiation and propagation.This study highlights a common method to improve the service life of high-carbon and high-alloy steels by adjusting the cryogenic se-quence.

关键词： M50 steel Cryogenic treatment Rolling contact fatigue life Carbide Twin

Acceleration of aging behavior and improvement of mechanical properties of extruded AZ80 alloy through(10–12) Twinning

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Journal of Magnesium and Alloys 2023年第2期11卷 671-683页

作者： Hyun Ji Kim Ye Jin Kim Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

The effects of pre-existing {10–12} extension Twins on the precipitation behavior of an extruded AZ80 material during aging and on its mechanical properties after peak aging are investigated. The material containing {10–12} Twins-which are formed by compression before aging(Twinned material)-has a finer grain size and higher dislocation density than the extruded material. Although the peak hardnesses of the Twinned and extruded materials are almost the same, the time to reach the peak hardness is considerably shorter in the former material than in the latter(4 h and 24 h, respectively). In the Twinned material, the high dislocation density of the {10–12} Twins promotes continuous precipitation, which results in the formation of numerous fine Mg17Al12precipitates within the Twins in the early stage of aging.The formation of these continuous precipitates reduces the driving force for discontinuous precipitation, which consequently suppresses the formation and growth of coarse Mg17Al12precipitates at the grain boundaries. Despite its shorter peak-aging time, the 4 h-peak-aged Twinned material shows higher tensile strength and elongation than the 24 h-peak-aged extruded material. These higher mechanical properties of the former material are attributed primarily to the presence of more abundant fine continuous precipitates, which are effective in strengthening the material, and less abundant coarse discontinuous precipitates, which can act as crack initiation sites. These results demonstrate that the introduction of {10–12} Twins into wrought Mg–Al-based alloys can accelerate the Mg17Al12precipitation kinetics considerably and improve the strength and ductility of the peak-aged alloys simultaneously.

关键词： AZ80 alloy Twin Aging Precipitation Tensile properties

Synergetic deformation mechanisms in an Mg-Zn-Y-Zr alloy with intragranular LPSO structures

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Journal of Magnesium and Alloys 2023年第5期11卷 1754-1768页

作者： Z.Z.Peng X.H.Shao Z.M.Liang D.L.Wang L.W.Wang X.L.Ma Hebei Key Laboratory of Material Near-Net Forming Technology School of Materials Science and EngineeringHebei University of Science and TechnologyShijiazhuang 050018China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Whenua RoadShenyang 110016China

Deformation kink is one of the important strengthening mechanisms of the long-period-stacking-ordered(LPSO)phase containing magnesium(Mg)alloys,while the deformation Twin is generally suppressed.To optimize the mechanical properties of LPSO containing Mg alloy by simultaneously exciting kink and Twin,we successfully prepared the Mg-Zn-Y-Zr alloy featuring intragranular LPSO phase and free grain boundary LPSO phase by homogenization.We unraveled the corresponding strengthening and toughening mechanisms through transmission electron microscopy characterization and theoretical analysis.The high strength and good plasticity of the homogenized alloy benefit from the synergistic deformation mechanism of multiple kinking and Twining in the grains.And the activation of kinking and Twinning depends on the thicknesses of LPSO lamellae and their relative spacing.These results may shed light on optimizing the design of Mg alloys regulating the microstructure of LPSO phases.

关键词： Mg alloy LPSO distribution Kink Twin Transmission electron microscopy

Formation of intermetallic compounds during reaction between Ti and Al-Mg alloys with various Mg contents

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Journal of Materials Science & Technology 2023年第28期159卷 225-243页

作者： Min Gao Tijun Chen State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou 730050China

The reactions between Ti and Al-Mg alloys were systematically investigated by heating the Ti/Al-Mg al-loy powder mixture compacts with Mg contents ranging from 5.09 to 40.36 wt.%at 660°C.Mg element in the Al-Mg alloys contributed to the breakage of the oxide films on the surfaces of the Ti and Al-Mg alloy powders,thus,promoting the reactions.In the samples with Mg contents varying from 5.09 wt.%to 25.93 wt.%,the first-formed intermetallic compound was Al_(18)Ti_(2)Mg_(3),and then Al_(3)Ti generated at the Al_(18)Ti_(2)Mg_(3)/Ti interface.Since the Mg content in the Al-Mg melts decreased during the subsequent heat-ing process,the previously formed Al_(18)Ti_(2)Mg_(3)in the Ti/Al-5.09Mg sample transformed into Al_(3)Ti accom-panied by the reaction of Al with Ti to newly form Al_(3)Ti,generating a single Al_(3)Ti phase.In contrast,the new formation of Al_(3)Ti and its transformation to Al_(18)Ti_(2)Mg_(3)proceeded continuously in the Ti/Al-13.54Mg and Ti/Al-25.94Mg samples,resulting in a mixture of Al_(18)Ti_(2)Mg_(3)and a little Al_(3)Ti residue.In the Ti/Al-40.54Mg sample,Al_(3)Ti was the unique reaction product throughout the heating process.The final Al_(3)Ti particles in the Ti/Al-5.09Mg sample were in a blocky shape,while they were in a plate-like form in the Ti/Al-40.54Mg sample,which was caused by the enhanced growth anisotropy due to the de-creased interfacial energy between Al_(3)Ti particles and Al-Mg melts with the increase of Mg content.A Twin plane re-entrant mechanism was suggested for the growth of Al_(18)Ti_(2)Mg_(3)particles,weakening the anisotropic growth caused by the directional supply of Ti atoms,and contributing to the blocky mor-phology of Al_(18)Ti_(2)Mg_(3)particles.In addition,the volume difference between the formed Al_(18)Ti_(2)Mg_(3)and consumed Ti was greater than that between the Al_(3)Ti and Ti,and the Al_(18)Ti_(2)Mg_(3)has worse plasticity than the Al_(3)Ti,resulting in the Al_(18)Ti_(2)Mg_(3)reaction product fracturing more easily during thickening,thus forming a petal-like struc

关键词： Mg content Intermetallic compound Phase transformation Morphology Twin

Hot Compression Mechanical Behavior of Solution Heat‑Treated and Pre‑aged Mg–Zn–Gd–Er Alloys

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Acta Metallurgica Sinica(English Letters) 2023年第3期36卷 469-485页

作者： Bo Che Liwei Lu Longfei Liu Yan Yang Wei Kang Jun Luo Zhiqiang Wu Yongfeng Qiu School of Materials Science and Engineering Hunan University of Science and TechnologyXiangtan 411201China College of Materials Science and Engineering Chongqing UniversityChongqing 400044China Hunan Provincial Key Laboratory of Vehicle Power and Transmission System Hunan Institute of EngineeringXiangtan 411104China Guiyang Aluminum Magnesium Design&Research Institute Co. LtdGuiyang 550081China School of Automation Central South UniversityChangsha 410083China

The mechanical behavior of solution heat-treated and pre-aged Mg–6Zn–1Gd–1Er alloys during hot compression(from 180 to 330℃)has been investigated.The results showed that the flow stress curves of the pre-aged sample(PAS)intersected with that of the solution heat-treated sample(SHTS)during hot compression.At 180℃,when the true strain is 0.27 and 0.47,the PAS showed larger and smaller stress(210.80 MPa vs.207.58 MPa and 205.67 MPa vs.207.93 MPa)than the SHTS,respectively.These phenomena were due to the stronger interaction of W phase and dislocations/Twins under the strain of 0.27,while dynamic recrystallization softening occurred under the strain of 0.47.When the temperature increased to 330℃,the flow stress of PAS and SHTS showed an opposite trend to that of 180℃.Continuous dynamic recrystallization and particle stimulated nucleation based on slip operations are the main deformation mechanisms under 330℃.At the true strain is 0.33 and 0.53,the PAS has smaller and larger stress(61.32 MPa vs.63.69 MPa and 58.75 MPa vs.57.09 MPa)than the SHTS,respectively.The increasing deformation resistance of dynamic precipitation improved the flow stress under smaller strain and dynamic recrystallization decreased the flow stress under high strain,which resulted the opposite phenomena of SHTS.

关键词： Mg-6Zn-1Gd-1Er alloy Mechanical behavior Precipitates Twin Dynamic recrystallization

Dynamic recrystallization mechanism of as-cast nickel base superalloy N10276 during primary hot working

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Journal of Iron and Steel Research(International) 2023年第4期30卷 825-837页

作者： Xin-chao Wang Yan Wang Xiao-jie Lian Mei Xu Li-feng Hou Ying-hui Wei College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024ShanxiChina State Key Laboratory of Advanced Stainless Steel Materials Taiyuan Iron and Steel(Group)Co.Ltd.Taiyuan 030003ShanxiChina Technology Center Shanxi Taiyuan Stainless Steel Co.Ltd.Taiyuan 030003ShanxiChina

The dynamic recrystallization(DRX)mechanism of as-cast nickel base superalloy N10276 during primary hot working was investigated by compression tests at temperatures of 1000–1200℃ and strain rates between 0.01 and 10 s^(-1).Optical microscopy,scanning electron microscopy,electron backscattered diffraction technique and transmission electron microscopy were used to characterize the evolution of microstructure.At higher deformation temperature or lower strain rate,the true stress–true strain curves exhibit the characteristic of a peak stress followed by a steady state flow stress under large strains,confirming the occurrence of DRX.The degree of DRX increases with elevating deformation temperature.With the progress of DRX,low angle grain boundaries gradually decrease,while high angle grain boundaries increase continuously.Microstructure studies have shown that discontinuous dynamic recrystallization is the main recrystallization mechanism.Since there are few original grain boundaries and Twin boundaries,and lack of second phase particles for particle stimulated nucleation,geometrically necessary boundaries are formed as supplementary nucleation sites through sub-grain boundary rotation and deformation Twin boundaries.The annealing Twins dominated by Σ3 grain boundaries are generated in large quantities during the growth of recrystallized grains.

关键词： Dynamic recrystallization mechanism As-cast superalloy N10276 Primary hot working Twin

Novel Twinned Al3Sc dendrites in as-casted Al-Sc alloy

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Rare Metals 2023年第3期42卷 838-843页

作者： Xing-Quan Wang Yu Wang Qian Jia Zhao-Chong Ding Jin-Jiang He Song-Xiao Hui State Key Laboratory of Nonferrous Metals and Processes GRIMAT Engineering Institute Co.Ltd.Beijing 101407China GRIKIN Advanced Material Co. Ltd. Beijing Technology Research Center for Sputtering Target Material Engineering of High Pure Metals

Al-Sc alloys with high Sc contents are served as sputtering targets for making high-performance piezoelectric devices.The micro structure of these alloys would affect the sputtering process and the final quality of the functional devices.In this study,the microstructure in as-c as ted Al-20%Sc(in atomic ratio)alloys is characterized and the feathery Al3Sc grains with Twin relationships are reported for the first time.The crystallographic features of Twined structures and growth directions are quantitatively analyzed by electron backscatter diffraction(EBSD)technique.

关键词： Al3Sc alloys Twin

Transfer or blockage:Unraveling the interaction between deformation Twinning and grain boundary in tantalum under shock loading with molecular dynamics

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Journal of Materials Science & Technology 2023年第25期156卷 118-128页

作者： Z.C.Meng M.M.Yang A.H.Feng S.J.Qu F.Zhao L.Yang J.H.Yao Y.Yang Q.B.Fan H.Wang Interdisciplinary Centre for Additive Manufacturing (ICAM) School of Materials and ChemistryUniversity of Shanghai for Science and TechnologyShanghai 200093China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China School of Materials Science and Engineering Tongji UniversityShanghai 201804China Academy for Advanced Interdisciplinary Studies Southern University of Science and TechnologyShenzhen 518055China National Key Laboratory of Science and Technology on Materials Under Shock and Impact School of Materials Science and EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401135China

The interaction between{112}deformation Twinning and grain boundary in coaxial polycrystalline tantalum under shock compression was studied with molecular dynamics simulation under different grain pair misorientation angles(MA)and geometric compatibility factor(m’).Generally,in the coaxial polycrystal,the value of MA determines the occurrence of Twin transfer(TT)or Twin blockage(TB),i.e.,Twin transfer occurs at MA≤29°with Twin blockage otherwise.Under TT,the value of m’affects the selection of Twin variants.,i.e.,the Twin system with a larger m’is easier to active.The morphology of Twin pairs is ruler-shaped and lenticular under TT and TB,respectively,with different thickening mechanisms,including grain boundary dislocation emission.

关键词： Plasticity Grain boundary Twin Atomistic simulation Tantalum