Ni_3Al合金的滑移特征及形变过程的晶界行为

SLIP FEATURE AND GRAIN BOUNDARY BEHAVIOURS OF Ni_3 Al ALLOYS DURING DEFORMATION

通过SEM动态拉伸形变试验,研究了具有各种化学成分和不同热处理态Ni_3Al合金的形变滑移特征,并用TEM观察了晶界区域的位错组态。研究结果表明,在含硼Ni_3Al合金的晶界附近存在一个过渡滑移区,该区域中滑移线重新取向或其它滑移系开动,从而产生了局部应变调节并使晶界应力集中松弛。硼降低了开动晶界位错源所需的应力并可能同时增加了位错源本身的数目。硼对Ni_3Al的韧化作用强烈受到基体Al含量、合金元素及热处理等因素的影响。

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.