X-Ray Diffuse Scattering and Martensitic Transformation in β(Au–Cd)+Cu Alloys

X-ray diffuse scattering measurements have been carried out on β-phase Au-47.5 at%Cd-0.75 at%Cu and Au-49.0 at%Cd-0.75 at%Cu alloys. Five notable features were found in the distribution of diffuse scattering: (i) diffuse sheets extending uniformly parallel to the (111) planes, (ii) diffuse streaks running through the fundamental reflection points in the [1\bar10] directions, (iii) diffuse peaks near q =(1/3)[110] along the [1\bar10] direction, (iv) diffuse peaks near q =(1/3)[112] along the [11\bar2] direction and (v) diffuse peaks near q =(3/4)[110] along the [110] direction. The intensity of these five kinds of anomalous diffuse scattering shows characteristic temperature dependence. The diffuse scattering is discussed in relation to the mechanism of martensitic transformation.