SLIP FEATURE AND GRAIN BOUNDARY BEHAVIOURS OF Ni_3 Al ALLOYS DURING DEFORMATION
Ni3Al合金的滑移特征及形变过程的晶界行为

The deformation behaviours of Ni_3Al alloys with various chemicalcompositions and subjected to different heat treatments were in situ observed underSEM. Moreover, in situ observations of slip trace were supplemented by the directobservation of dislocation arrangements under TEM. In B-doped Ni_3Al alloys it isshown that close to the grain boundary there exists a thin slip transition region,within which slip lines are reoriented or other slip systems are operated to producea local strain accommodation and to relax the stress concentration at grain bound-aries. Boron seems to lower the stress for dislocation generation from the grainboundary or to ease the cross-slip close to the boundary,and also to increase the numberof dislocation sources. However, B-enhenced ductility is seriously affected by alloystoichiometry, the addition of a tertiary alloy element and heat treatment, etc.