晶粒尺寸对Cu-30%Zn合金形变孪晶厚度的影响

Grain Size Effect on Thickness of Deformation in Cu-Zn Alloys

对于面心立方结构的纳米金属,晶粒尺寸对孪生厚度（孪生核）的影响虽已有研究,但仍有待深入.本论文以Cu-30％Zn合金为模型材料,通过高压扭转变形技术、等径角挤压连同轧制技术变形得到晶粒尺寸在5～500nm的样品.透射电子显微镜观察发现：变形孪晶的片层厚度随晶粒尺寸的减小而减小,当晶粒尺寸小于20nm以后,孪晶厚度为（111）晶面间距（层错）;另外,层错存在于各个不同尺寸范围的晶粒内,表明层错不受晶粒尺寸影响.研究结果表明在低层错能超细晶材料中,孪生变形是通过从晶界连续发射不全位错（层错）形成的.

For nanostructured fcc metals, grain size influence on deformation twinning and stacking fault has been investigated in literature, nevertheless, it still need further study to go deep for a better understanding. We selected Cu-30%Zn alloy as a model material. High pressure torsion （HPT）, equal channel pressing （ECAP） followed by cold rolling were used to achieve a wide range of grain size from about 5 nm to 500nm. It was found that, with decreasing the grain size down to 20nm, twin thickness gradually reduces to one （111） atomic plane space （stacking fault） ; while stacking fault exists within grains with the grain sizes of whole range. Our results indicate the twinning in ultra-fine alloys with low stacking fault energy is operated via partial dislocation （stacking fault） emission from grain boundaries.