| Popis: |
The temperature dependence of the dynamic elastic constants (Moduli of Compliance, S11, S12 and S44) of body-centered cubic Au-Cd alloys that undergo diffusionless phase change, has been determined as a function of composition variation within the beta phase and heat treatment prior to measurement. The results are consistent by comparison with compressibility calculations and data available for an isomorphous material, beta brass. Derived quantities are similarly comparable. The abnormally high elastic shear anisotropy, 2 (S 11 –S 12 ) S 44 , increasing with decreasing temperature, leads to the consideration of an elastic shear anisotropy criterion for diffusionless transformation of body-centered cubic beta-phase alloys. 47.5 at. per cent Cd alloys water-quenched from 500°C and 550°C yield elastic constant data and a diffusionless transformation temperature consistent with that for a 50 at. per cent Cd alloy. An interpretation of the latter phenomena is offered, based upon the elastic interaction of quenched-in vacancies with neighboring metal ions. |
