Superplasticity and cavity stringers in a multiphase NiAl-based intermetallic alloy

A multiphase NiAl-based intermetallic alloy has been observed to display superplastic behavior from 1123 to 1223 K and strain rates ranging from 3.3×10−2 to 2.2×10−4 s−1. A grain boundary sliding-based mechanism is proposed as being responsible for the observed superplasticity. After superplastic deformation, it is observed that cavities are usually aligned parallel to the extrusion direction and the tensile axis. The formation of cavity stringers is suggested to be essentially related not only to cavity nucleation site but also to the nature and characteristics of superplastic deformation.