Elastic Anomalies and Special Mode Softening Preceding Martensitic Phase Transition in Au-Ag-Cd Alloys

Several kinds of elastic anomalies occur as the preceding phenomena of the martensitic phase transition in Au-Ag-Cd alloys. Besides the softening of C '=( C 11 - C 12 )/2, both C ' and C 44 exhibit cooperative and non-linear changes near the transition point. Due to such changes, another type of the softening is induced in the special mode, which is responsible to the formation of close packed planes in the martensite. Based on the obtained results, nature of the special mode softening and the transition mechanism in the β phase alloys are briefly considered.