论文部分内容阅读
利用低温力学测试系统研究了电化学沉积纳米Ni在77K温度下的压缩行为.室温下纳米Ni的屈服强度为2.0GPa,77K温度下的屈服强度为3.0GPa,压缩变形量则由室温的10%左右下降到5%.借助应变速率敏感指数、激活体积、扫描电子显微和高分辨透射电子显微分析,对纳米Ni的塑性变形机制进行了表征.研究表明,在77K温度下的塑性变形主要是由晶界-位错协调变形主导,晶界本征位错弓出后无阻碍地在晶粒内无位错区运动,直至在相对晶界发生类似切割林位错行为.同时分析了弓出位错的残留位错部分在协调塑性变形时起到的增加应变相容性和减小应力集中的作用.利用晶界-位错协调机制和残留位错运动与温度及缺陷的相关性揭示了纳米Ni室温和77K温度压缩性能差异的内在原因.
The compressive behavior of nano-Ni deposited at 77K was investigated by using a low temperature mechanical testing system.The yield strength of nano-Ni at room temperature was 2.0GPa, the yield strength at 77K was 3.0GPa, the compressive deformation was from 10% About 5% .The plastic deformation mechanism of nano-Ni was characterized by means of strain rate sensitivity index, activation volume, scanning electron microscopy and high-resolution transmission electron microscopy.The results show that the plastic deformation at 77K is mainly Is dominated by the coordinated deformation of the grain boundaries and dislocations, and the grain boundary intrinsic dislocations bow out unobstructedly in the dislocation-free zone within the grains until a similar dislocation behavior of the cutting forest occurs at the relative grain boundaries. The residual dislocation part of dislocation plays the role of increasing the strain compatibility and reducing the concentration of stress during the coordination plastic deformation.The correlation between grain boundary-dislocation coordination mechanism and residual dislocation movement and temperature and defects is revealed The inherent causes of the difference in the compressive properties of nano-Ni between room temperature and 77K.