Influence of texture and hydrostatic pressure on the room temperature compression of NiAl polycrystals

Abstract

Compression of NiAl polycrystals was carried out at room temperature under atmospheric as well as 0.4 GPa confining pressure at constant strain rate. The stress–strain curves show that the strength as well as the work-hardening rate is generally higher when deformed under hydrostatic pressure. Moreover, there is a strong plastic anisotropy, that is, samples having a 〈100〉 crystallographic preferred orientation parallel to the compression axis are much harder than those having 〈110〉 and 〈111〉. Similarly, the frequency of microcracking shows the same tendency. It seems that the microcracks in the samples deformed under confining pressure mainly result from internal stresses released after unloading. The strength of the differently textured samples at elevated strains correlates with the Taylor energy calculated. These calculations also explain for certain textures the deviation from a homogeneous shape change during compression towards plane–strain deformation. The textural changes produced by deformation are simulated with the Taylor model.