Effect of Existing Twin Boundaries in Martensite on the Rubber-Like Behavior and Ageing Effect in Au-Cd Alloys

¹ University of Tsukuba, Institute of Materials Science, Tsukuba, Ibaraki 305, Japan
² Teikyo University, Department of Materials Science and Engineering, Toyosatodai, Utsunomiya 320, Japan

Abstract

The effect of existing twin (or intervariant) boundaries on both the rubber-like behavior and the ageing effect (Af temperature increase) was studied by using γ₂' (orthorhombic) and ζ₂'(trigonal) martensites in Au-Cd alloys. A typical rubber-like behavior was observed even in a single-variant specimen of γ₂' martensite, which proves that the presence of twin boundaries is not the necessary condition for the rubber-like behavior. Thus, the previously proposed mechanism for pinning of boundaries was denied. However, the observed Af temperature increase in the ζ₂' martensite was more pronounced in the specimen with twin boundaries (multivariant state) rather than that without twin boundaries (single-variant state). Thus, it was found that the presence of twin boundaries affects the development of ageing effect though it is not the direct origin for the phenomenon.