Deformation mechanisms in intermetallic compounds based on Nb 3Al

Abstract

Some mechanical properties and deformation mechanisms of two compounds based on Nb 3Al, both containing 15%Al (atomic per cent) and one with 10% Ti and the other with 40% Ti, were determined. The compounds can be prepared as single-phase material such that they exhibit the B2 crystal structure; in the heat-treated condition a second phase may be precipitated, for example with the A15 crystal structure in the case of the 10Ti alloy. The compounds are strong over a range of temperatures, at least up to 900 °C, and are inherently ductile. The compounds deform by activation of one or more of the following slip systems, namely 〈111〉{110}, 〈111〉{112} and 〈111〉{123}. The dislocations are present in the form of dissociated superpartial pairs, each with Burgers vector b given by b = 1 2 〈111〉 , which bound a ribbon of antiphase boundary (APB). From the separation of the partial dislocations, the APB energy on the {110} planes were found to be approximately 150 mJ m −2 and approximately 15 mJ m −2 for the 10 Ti and 40 Ti containing alloys respectively. The A15 phase which appears upon heat treatment deforms by glide of 〈001〉{100} and 〈001〉{021}, as determined previously in other A15 compounds.