Microstructures of some intermetallic compounds deformed by impact loading

Abstract

A number of intermetallic compounds such as Ni 3Al, cubic (Al, Mn) 3Ti, CuZn, CoTi, TiAl and Ti 3Al have been deformed by explosive-impact testing using a copper projectile with a velocity between 0.6 and 1.6 km s −1. The corresponding strain rate is in the range of 3–8 × 10 4 s −1. Some of the intermetallic compounds deformed by such impact tests exhibited deformation structures significantly different from those after quasi-static loading. In a two-phase TiAl alloy, a twin-like band structure, whose interfaces can be indexed to be {577}, has been found to form under impact loading. In Ti 3Al, basal slip is more frequently observed under impact loading than under quasi-static loading. The case of basal slip relative to slip on other slip systems seems to be enhanced under impact loading. In CoTi, slip along 〈111〉 as well as that along 〈001〉 are observed under impact loading conditions. Under quasi-static deformation, slip of the latter type is the major deformation mode of this compound, but the former one has been observed in only a very limited orientation region. Twinning is the preferred mode of deformation in the two-phase TiAl alloy deformed under both impact and quasi-static loading. Under deformation conditions achieved by impact loading in our powder gun recovery system, deformation twinning cannot be induced in compounds in which twinning is not a natural deformation mode.