本文采用聚焦离子束法(Focused Ion Beam,FIB)对<110>取向铱(Ir)单晶进行切割,加工出直径为400~3000nm的微柱样品,随后在带有平压头的纳米压痕仪上进行压缩试验来研究其力学行为。Ir单晶微柱压缩的工程应力-应变曲线表明,流变应...本文采用聚焦离子束法(Focused Ion Beam,FIB)对<110>取向铱(Ir)单晶进行切割,加工出直径为400~3000nm的微柱样品,随后在带有平压头的纳米压痕仪上进行压缩试验来研究其力学行为。Ir单晶微柱压缩的工程应力-应变曲线表明,流变应力随着微柱直径的减小而增加,即存在"尺度效应",且流变应力与微柱直径符合幂律关系,同时工程应力-应变曲线上出现了离散的"应变陡增",利用"位错匮乏"机制能够对这种现象进行较好的解释。微柱压缩变形后的扫描电镜(SEM)图像表明微柱的滑移方式为多滑移,并且滑移与微柱直径相关。展开更多
Serrated flow has been primarily studied at the macron scale,yet the length and times scales at which the solute-meditated dislocation pinning and de-pinning processes that underlie the phenomenon occur are largely in...Serrated flow has been primarily studied at the macron scale,yet the length and times scales at which the solute-meditated dislocation pinning and de-pinning processes that underlie the phenomenon occur are largely inaccessible by macroscopic tests.Moreover,direct insights into the dominant slip systems in the serrated flow regime,which is particularly critical in Mg alloys given their high plastic anisotropy,requires the use of small-scale testing methods such as microcompression.Thus,in this work,a combination of microcompression and TEM based EDS/STEM measurements have used to critically study the temperature and strain rate dependences in single crystals of pure Mg and a Mg-Gd alloy oriented for twinning,basal-,prismatic-,and pyramidal-slip.The results provide compelling evidence that the solute drag mechanism underlie serrated flow in the alloy;they also show that serrated flow in Mg alloys is markedly anisotropic.This anisotropy is caused by differences between the Burgers vector for slip/twinning,and between the impurity diffusivity along/perpendicular to the basal plane.展开更多
文摘本文采用聚焦离子束法(Focused Ion Beam,FIB)对<110>取向铱(Ir)单晶进行切割,加工出直径为400~3000nm的微柱样品,随后在带有平压头的纳米压痕仪上进行压缩试验来研究其力学行为。Ir单晶微柱压缩的工程应力-应变曲线表明,流变应力随着微柱直径的减小而增加,即存在"尺度效应",且流变应力与微柱直径符合幂律关系,同时工程应力-应变曲线上出现了离散的"应变陡增",利用"位错匮乏"机制能够对这种现象进行较好的解释。微柱压缩变形后的扫描电镜(SEM)图像表明微柱的滑移方式为多滑移,并且滑移与微柱直径相关。
文摘Serrated flow has been primarily studied at the macron scale,yet the length and times scales at which the solute-meditated dislocation pinning and de-pinning processes that underlie the phenomenon occur are largely inaccessible by macroscopic tests.Moreover,direct insights into the dominant slip systems in the serrated flow regime,which is particularly critical in Mg alloys given their high plastic anisotropy,requires the use of small-scale testing methods such as microcompression.Thus,in this work,a combination of microcompression and TEM based EDS/STEM measurements have used to critically study the temperature and strain rate dependences in single crystals of pure Mg and a Mg-Gd alloy oriented for twinning,basal-,prismatic-,and pyramidal-slip.The results provide compelling evidence that the solute drag mechanism underlie serrated flow in the alloy;they also show that serrated flow in Mg alloys is markedly anisotropic.This anisotropy is caused by differences between the Burgers vector for slip/twinning,and between the impurity diffusivity along/perpendicular to the basal plane.
