Relation Between Orthorhombic Distortions and Transformation Temperatures in β-Au-Cd-Ag Alloys

Department of Physics, Nara Women's University, Nara 630, Japan

Abstract

The change in the orthorhombic distortion of the 2H martensite in semi-binary Au-47.5at%Cd-Ag alloys has been measured as a function of Ag concentration and temperature by the X-ray diffraction method. The following results are obtained. The volumes of the β-phase at 298 K and the martensite at 93 K keep constant against Ag concentration. This result means that the effective size of Ag is almost the same as that of Au. The orthorhombic distortion is increased with increasing Ag concentration in spite of the same effective size of Au and Ag. This result suggests that the orthorhombic distortion is essentially due to electronic effect. The martensitic transformation takes place with the same value of the orthorhombic distortion, which result gives an evidence that the orthorhombic distortion is responsible for the stability of the martensite.