Fe—3%Si单晶体裂纹尖端位错行为及氢效应的TEM动态观察

IN-SITU OBSERVATIONS ON DISLOCATION BEHAV IOR AND THE EFFECT OF HYDROGEN NEAR THE CRACK-TIP IN Fe-3%Si SINGLE CRYSTAL BY TEM

在透射电镜中对 Fe-3%Si 单晶体薄膜进行拉伸试验,观察了在受力状态下裂纹尖端的位错行为及固溶氢的影响。结果表明,在受力时裂尖会自动发射位错。位错一旦从裂尖发射,便很快离开裂纹尖端以反塞积群形式存在于塑性区中。在裂纹尖端与塑性区之间存在一无位错区(DFZ)。裂纹扩展包括裂尖发射位错的塑性过程以及 DFZ 解理的脆性过程。固溶的氢改变了裂纹尖端的位错分布,促进了位错从裂尖发射,致使 DFZ 的长度减小甚至消失。

Dislocation behavior and effect of hydrogen have been observed near thecrack-tip in Fe-3%Si single crystal during in-situ deformation in an electron microscope.It has been found that a number of dislocations were emitted from the crack-tip duringdeformation and moved away quickly from the crack-tip region creating a dislocation-freezone (DFZ).The dislocations stored in the plastic zone were in a form of an inversepile-up.The propagation of the crack-tip includes two processes,i.e.the plastic process inwhich a number of dislocations were emitted from the crack-tip by crack-tip deformationand the brittle process in which the cleavage of DFZ occured.The solute hydrogen can change the distribution of dislocations near the crack-tip andcan lead to the diminution and even disappearance of the DFZ.