This study investigates the effect of {10-12} deformation twins on the continuous precipitation behavior of an extruded Mg-8.0Al-0.5Zn-0.2Mn(AZ80) alloy during aging. The extruded AZ80 alloy is compressed along the tr...This study investigates the effect of {10-12} deformation twins on the continuous precipitation behavior of an extruded Mg-8.0Al-0.5Zn-0.2Mn(AZ80) alloy during aging. The extruded AZ80 alloy is compressed along the transverse direction to introduce {10-12} twins,followed by an aging treatment at 300 ℃. The extruded material exhibits a twin-free microstructure with low internal strain energy, whereas the pre-twinned material possesses abundant {10-12} twins and has high internal strain energy. The aging results reveal that the peak-aging time of the pre-twinned material(1 h) is one-eighth of that of the extruded material(8 h). Although Mg_(17)Al_(12) continuous precipitates(CPs)are observed in both the peak-aged materials, these CPs are much smaller and more densely distributed in the pre-twinned material despite the significantly shorter aging time. The CPs size in the peak-aged materials increases in the following order: twinned region in the pre-twinned material(0.47 μm) < residual matrix region in the pre-twinned material(1.71 μm) < matrix region in the extruded material(2.55 μm).Moreover, the CPs number density in the twinned region of the pre-twinned material is approximately 11 times higher than that in the matrix region of the extruded material. The peak-aged pre-twinned material exhibits significantly higher tensile strength and ductility than the peak-aged extruded material. These results demonstrate that the formation of {10-12} twins in the extruded AZ80 alloy substantially accelerates the static precipitation of CPs during aging at 300 ℃ and improves the tensile properties of the peak-aged material.展开更多
In this work,we carried out three-dimensional(3D)atomic-scale study on the growth characteristics of{10-12}twin in magnesium(Mg).The study was performed by MD simulations on Mg single crystals with an initial twin nuc...In this work,we carried out three-dimensional(3D)atomic-scale study on the growth characteristics of{10-12}twin in magnesium(Mg).The study was performed by MD simulations on Mg single crystals with an initial twin nucleus structures.A detailed atomistic analysis reveals that a stabilized 3D{10-12}twin nucleus is bounded by basal/prismatic(BP)interfaces,prismatic/basal(PB)interfaces,and{10-11}interfaces.Later,a{10-12}twin boundary(TB)occurs at the junction of the BP and PB interface with the growth of the twin nucleus.In this process,two twinning mechanisms are involved:a pure-shuffle mechanism in which{10-11}interface migration along the[11-20]direction is mediated by atomic shuffle,and a glide-shuffle mechanism in which BP/PB and{10-12}TB movements are realized by the migration of disconnections along the relevant interfaces.In addition,we systematically investigate the stress state associated with the activation of twinning,aiming to discover the intrinsic relationship of the elastic stress field to twin growth on an atomic scale.The results suggest that the elastic stress in the matrix is an important driving force for twin growth,much similar to what stress does for a crack.In addition,it is rather remarkable that the{10-11}interface has a greater ability to migrate than other interfaces,and this is thought to be a main factor for the rapid growth of a{10-12}twin.展开更多
基金supported by the National Research Foundation of Korea (NRF) (grant no.2019R1A2C1085272) funded by the Ministry of Science,ICTFuture Planning (MSIP,South Korea)。
文摘This study investigates the effect of {10-12} deformation twins on the continuous precipitation behavior of an extruded Mg-8.0Al-0.5Zn-0.2Mn(AZ80) alloy during aging. The extruded AZ80 alloy is compressed along the transverse direction to introduce {10-12} twins,followed by an aging treatment at 300 ℃. The extruded material exhibits a twin-free microstructure with low internal strain energy, whereas the pre-twinned material possesses abundant {10-12} twins and has high internal strain energy. The aging results reveal that the peak-aging time of the pre-twinned material(1 h) is one-eighth of that of the extruded material(8 h). Although Mg_(17)Al_(12) continuous precipitates(CPs)are observed in both the peak-aged materials, these CPs are much smaller and more densely distributed in the pre-twinned material despite the significantly shorter aging time. The CPs size in the peak-aged materials increases in the following order: twinned region in the pre-twinned material(0.47 μm) < residual matrix region in the pre-twinned material(1.71 μm) < matrix region in the extruded material(2.55 μm).Moreover, the CPs number density in the twinned region of the pre-twinned material is approximately 11 times higher than that in the matrix region of the extruded material. The peak-aged pre-twinned material exhibits significantly higher tensile strength and ductility than the peak-aged extruded material. These results demonstrate that the formation of {10-12} twins in the extruded AZ80 alloy substantially accelerates the static precipitation of CPs during aging at 300 ℃ and improves the tensile properties of the peak-aged material.
基金The authors are grateful for the support from the National Natural Science Foundation of China(No.51471038)the Fundamental Research Funds for the Central Universities(No.2018CDPTCG0001/42)the National special support program for high-level personnel recruitment.
文摘In this work,we carried out three-dimensional(3D)atomic-scale study on the growth characteristics of{10-12}twin in magnesium(Mg).The study was performed by MD simulations on Mg single crystals with an initial twin nucleus structures.A detailed atomistic analysis reveals that a stabilized 3D{10-12}twin nucleus is bounded by basal/prismatic(BP)interfaces,prismatic/basal(PB)interfaces,and{10-11}interfaces.Later,a{10-12}twin boundary(TB)occurs at the junction of the BP and PB interface with the growth of the twin nucleus.In this process,two twinning mechanisms are involved:a pure-shuffle mechanism in which{10-11}interface migration along the[11-20]direction is mediated by atomic shuffle,and a glide-shuffle mechanism in which BP/PB and{10-12}TB movements are realized by the migration of disconnections along the relevant interfaces.In addition,we systematically investigate the stress state associated with the activation of twinning,aiming to discover the intrinsic relationship of the elastic stress field to twin growth on an atomic scale.The results suggest that the elastic stress in the matrix is an important driving force for twin growth,much similar to what stress does for a crack.In addition,it is rather remarkable that the{10-11}interface has a greater ability to migrate than other interfaces,and this is thought to be a main factor for the rapid growth of a{10-12}twin.
