The microstructure and mechanical properties of Mg−4.5Al−2.5Zn−0.3Mn−0.2Ca(wt.%,designated as AZ42)alloys in extruded(at extrusion ratios of 28,20 and 11.5)and peak-aged states were investigated,by using optical micro...The microstructure and mechanical properties of Mg−4.5Al−2.5Zn−0.3Mn−0.2Ca(wt.%,designated as AZ42)alloys in extruded(at extrusion ratios of 28,20 and 11.5)and peak-aged states were investigated,by using optical microscopy,scanning electron microscopy,energy dispersive spectrometry and electron backscatter diffraction.The results show that extrusion produces a typical basal fiber texture and streamlines of second phases.All samples exhibit the lowest Schmid factor of basal slip(SFb)and the superior tensile yield strength(TYS)along extrusion direction(ED).The sample with extrusion ratio of 20 exhibits the largest average grain size,but the smallest SFb which compensates for the disadvantage of grain coarsening and maintains the strength.After being peak-aged at 175℃for 48 h,the sample with the extrusion ratio of 20 shows the optimal TYS along all the directions,compared to the other samples.This hopes to provide useful information for optimizing the deformation parameters of the AZ42 alloys.展开更多
The rapidly increasing scientific interest in 3D-printed high-entropy alloys(HEAs)necessitates the understanding of their deformation mechanisms.Here,we present the grain rotation behavior of a nearly equiatomic CrMnF...The rapidly increasing scientific interest in 3D-printed high-entropy alloys(HEAs)necessitates the understanding of their deformation mechanisms.Here,we present the grain rotation behavior of a nearly equiatomic CrMnFeCoNi HEA fabricated with laser-beam powder bed fusion via quasi in-situ electron backscatter diffraction(EBSD)observations during compressive deformation.The rotation paths of grains can be predicted via a new lattice reorientation factor(m_(A)),defined as the average of primary and secondary slip Schmid factors.The grains that initially have their〈111〉directions oriented close to the loading direction with low-to-intermediate m_(A)values tend to rotate towards the〈101〉pole.The grains initially oriented in the center of inverse pole figures with high m_(A)values develop multiple rotation paths pointing away from the〈001〉pole.The cube-oriented grains with their〈001〉directions close to the loading direction undergo face-centered cubic(FCC)-to-hexagonal close-packed(HCP)phase transformation due to the activation of octahedral slip involving multiple slip systems.This transformation can be well elucidated via a modified parameter,defined as the average of four maximum Schmid factors on each of four{111}slip/twinning planes in FCC crystals.The findings provide new insights into the underlying mechanisms for deformation-induced grain rotation and phase transformation,and help pave the way for developing advanced HEAs via transformation-induced plasticity.展开更多
A statistical analysis of the twinning behavior in a basal-textured Mg sheet under hard orientation loading was performed at strain rates of 1×10^(-5) and 1×10^(-1) s^(-1) with grain sizes of 70 and 20µ...A statistical analysis of the twinning behavior in a basal-textured Mg sheet under hard orientation loading was performed at strain rates of 1×10^(-5) and 1×10^(-1) s^(-1) with grain sizes of 70 and 20µm.There were 1609 tension twins identified including adequate(51%)anomalous twins(Schmid factor m<0).Twin variant selection exhibited almost no grain size or strain rate effects.Most twin variants(74%)correlated well with the proposed normalized Schmid factor(mnor).The Luster-Morris parameter(m′)values failed to correlate with the twin transmission,while 96%of transmitted pairs exhibited large mnor or normalized m′(m′nor)values.Twin transmission occurred more frequently at lower grain boundary misorientation angles(10°-30°).The active anomalous twins correlated well with m of the prismatic slip.The present work provided a statistical perspective that,the mnor and m′nor can correlate the anomalous twinning rather than m and m′.The local condition also played a critical role in anomalous twinning behavior.展开更多
The selection of twin variants plays a critical role in shaping the deformation texture and mechanical properties of magnesium alloys that are limited by slip systems and diverse twinning modes.In this study,we invest...The selection of twin variants plays a critical role in shaping the deformation texture and mechanical properties of magnesium alloys that are limited by slip systems and diverse twinning modes.In this study,we investigated the twin variant selection and the effect of twinning activity on the strain hardening of a hot-rolled AZ31 magnesium alloy by quasi-in-situ EBSD.Moreover,the Schmid factors and the displacement gradient tensors were computed to evaluate the activation of twin variants.The results reveal that the yield strength increased progressively after each deformation step,driven by grain subdivision and texture hardening induced by extension{1012}twinning and the Basinski effect at large strains.The nucleation and growth of the{1012}twins occurred either sequentially or simultaneously during the plastic deformation.At low plastic strains,the activation of most twin variants followed the high Schmid factor criterion while the other twin variants with lower Schmid factors were activated due to the interactions with preexisting twins characterized by high misorientation angles(around 60°).Additionally,this non-Schmid factor scenario was also attributed to low coordinated strain requirements from neighboring grains,showing the critical role of local deformation accommodation in the twinning process.These findings advance the fundamental understanding of the twin variant selection and its implications for the microstructure-property relationship in magnesium alloys for structural applications.展开更多
采用100 k N servo-hydraulic MTS型试验机对挤压态AZ31镁合金进行温度为350℃、应变速率为0.3 s-1和不同应变量下的热压缩;利用X射线衍射(XRD)测量不同应变量下的织构,并利用取向分布函数计算其织构类型,分析织构转变;通过电子背散射...采用100 k N servo-hydraulic MTS型试验机对挤压态AZ31镁合金进行温度为350℃、应变速率为0.3 s-1和不同应变量下的热压缩;利用X射线衍射(XRD)测量不同应变量下的织构,并利用取向分布函数计算其织构类型,分析织构转变;通过电子背散射衍射技术(EBSD)分析孪生的形成情况。同时,计算不同滑移系和孪生的斯密特因子,分析不同滑移系和孪生开启的先后次序。结果表明:变形初期,由于拉伸孪生的出现导致(0001)]0110[和(0001)]0112[织构的形成,并随应变量的增加,发生动态再结晶,)0101([0001]和)0121([0001]纤维织构完全由(0001)]0110[和(0001)]0112[织构代替;在变形初期,大部分晶粒先产生拉伸孪生,接着发生二阶锥面滑移。展开更多
基金supported by the National Natural Science Foundation of China(No.51904036)the Hunan Provincial Key Research and Development Program,China(No.2023GK2049)+2 种基金Changsha Municipal Natural Science Foundation,China(Nos.kq2402016,kq2402014)the Postgraduate Scientific Research Innovation Project of Hunan Province,China(No.CX20240772)the Sichuan Science and Technology Program,China(No.2024NSFSC0151)。
文摘The microstructure and mechanical properties of Mg−4.5Al−2.5Zn−0.3Mn−0.2Ca(wt.%,designated as AZ42)alloys in extruded(at extrusion ratios of 28,20 and 11.5)and peak-aged states were investigated,by using optical microscopy,scanning electron microscopy,energy dispersive spectrometry and electron backscatter diffraction.The results show that extrusion produces a typical basal fiber texture and streamlines of second phases.All samples exhibit the lowest Schmid factor of basal slip(SFb)and the superior tensile yield strength(TYS)along extrusion direction(ED).The sample with extrusion ratio of 20 exhibits the largest average grain size,but the smallest SFb which compensates for the disadvantage of grain coarsening and maintains the strength.After being peak-aged at 175℃for 48 h,the sample with the extrusion ratio of 20 shows the optimal TYS along all the directions,compared to the other samples.This hopes to provide useful information for optimizing the deformation parameters of the AZ42 alloys.
基金the Natural Sciences and Engineering Research Council of Canada(NSERC),Natural Resources Canada(NRCan),Alberta Innovates,and the National Natural Science Foundation of China(NSFC)(Grant Nos.52271012 and 51871168)for the financial support.
文摘The rapidly increasing scientific interest in 3D-printed high-entropy alloys(HEAs)necessitates the understanding of their deformation mechanisms.Here,we present the grain rotation behavior of a nearly equiatomic CrMnFeCoNi HEA fabricated with laser-beam powder bed fusion via quasi in-situ electron backscatter diffraction(EBSD)observations during compressive deformation.The rotation paths of grains can be predicted via a new lattice reorientation factor(m_(A)),defined as the average of primary and secondary slip Schmid factors.The grains that initially have their〈111〉directions oriented close to the loading direction with low-to-intermediate m_(A)values tend to rotate towards the〈101〉pole.The grains initially oriented in the center of inverse pole figures with high m_(A)values develop multiple rotation paths pointing away from the〈001〉pole.The cube-oriented grains with their〈001〉directions close to the loading direction undergo face-centered cubic(FCC)-to-hexagonal close-packed(HCP)phase transformation due to the activation of octahedral slip involving multiple slip systems.This transformation can be well elucidated via a modified parameter,defined as the average of four maximum Schmid factors on each of four{111}slip/twinning planes in FCC crystals.The findings provide new insights into the underlying mechanisms for deformation-induced grain rotation and phase transformation,and help pave the way for developing advanced HEAs via transformation-induced plasticity.
基金supported by the National Natural Science Foundation of China(Nos.52171125,52071178)。
文摘A statistical analysis of the twinning behavior in a basal-textured Mg sheet under hard orientation loading was performed at strain rates of 1×10^(-5) and 1×10^(-1) s^(-1) with grain sizes of 70 and 20µm.There were 1609 tension twins identified including adequate(51%)anomalous twins(Schmid factor m<0).Twin variant selection exhibited almost no grain size or strain rate effects.Most twin variants(74%)correlated well with the proposed normalized Schmid factor(mnor).The Luster-Morris parameter(m′)values failed to correlate with the twin transmission,while 96%of transmitted pairs exhibited large mnor or normalized m′(m′nor)values.Twin transmission occurred more frequently at lower grain boundary misorientation angles(10°-30°).The active anomalous twins correlated well with m of the prismatic slip.The present work provided a statistical perspective that,the mnor and m′nor can correlate the anomalous twinning rather than m and m′.The local condition also played a critical role in anomalous twinning behavior.
文摘The selection of twin variants plays a critical role in shaping the deformation texture and mechanical properties of magnesium alloys that are limited by slip systems and diverse twinning modes.In this study,we investigated the twin variant selection and the effect of twinning activity on the strain hardening of a hot-rolled AZ31 magnesium alloy by quasi-in-situ EBSD.Moreover,the Schmid factors and the displacement gradient tensors were computed to evaluate the activation of twin variants.The results reveal that the yield strength increased progressively after each deformation step,driven by grain subdivision and texture hardening induced by extension{1012}twinning and the Basinski effect at large strains.The nucleation and growth of the{1012}twins occurred either sequentially or simultaneously during the plastic deformation.At low plastic strains,the activation of most twin variants followed the high Schmid factor criterion while the other twin variants with lower Schmid factors were activated due to the interactions with preexisting twins characterized by high misorientation angles(around 60°).Additionally,this non-Schmid factor scenario was also attributed to low coordinated strain requirements from neighboring grains,showing the critical role of local deformation accommodation in the twinning process.These findings advance the fundamental understanding of the twin variant selection and its implications for the microstructure-property relationship in magnesium alloys for structural applications.
文摘采用100 k N servo-hydraulic MTS型试验机对挤压态AZ31镁合金进行温度为350℃、应变速率为0.3 s-1和不同应变量下的热压缩;利用X射线衍射(XRD)测量不同应变量下的织构,并利用取向分布函数计算其织构类型,分析织构转变;通过电子背散射衍射技术(EBSD)分析孪生的形成情况。同时,计算不同滑移系和孪生的斯密特因子,分析不同滑移系和孪生开启的先后次序。结果表明:变形初期,由于拉伸孪生的出现导致(0001)]0110[和(0001)]0112[织构的形成,并随应变量的增加,发生动态再结晶,)0101([0001]和)0121([0001]纤维织构完全由(0001)]0110[和(0001)]0112[织构代替;在变形初期,大部分晶粒先产生拉伸孪生,接着发生二阶锥面滑移。
