Effect of Existing Twin Boundaries in Martensite on the Rubber-Like Behavior and Ageing Effect in Au-Cd Alloys
University of Tsukuba, Institute of Materials Science, Tsukuba, Ibaraki 305, Japan
2 Teikyo University, Department of Materials Science and Engineering, Toyosatodai, Utsunomiya 320, Japan
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.
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