纳米压痕位移突变机理研究

用铁和ZnO单晶研究纳米压入时的位移突变和蠕变突变.结果表明,电解抛光的纯铁压入时会出现位移突变,突变前后的载荷一位移曲线明显不同,它对应表面膜破裂.而对于ZnO单晶来说,突变前后载荷一位移曲线变化不大,该突变意味着位错的爆发式发射.随加载速率降低,发生位移突变的临界载荷PC也下降.当P＞PC恒载荷蠕变时,位移缓慢升高直至饱和,但无突变;如P＜PC,恒载荷下保持一定时间就会发生蠕变突变,随后位移缓慢升高至饱和;如P＜P++(门槛载荷),则不发生蠕变和蠕变突变.

MECHANISTIC STUDY ON NANOINDENTATION CREEP IN SINGLE CRYSTALS

Excursion in depth during loading or creeping under sustained load of iron steel and ZnO single crystals as well as the effect of hydrogen have been investigated by means of nanoindentation. Results show that there is sudden excursion in displacement during nanoindentation in electropolished specimens. The curves are quite different before and after the excursion, which is ascribed to film breaking. The change of load and depth is little for the ZnO single crystal. This indicates that the excursion was caused by dislocation emission. The critical load P_C corresponding to the excursion decreased with decreasing the loading rate. During creeping under sustained load of P>P_C, the displacement will increase slowly to a saturation value, and no displacement burst. During creeping under sustained load of P