Thermal Expansion and Elastic Constants of β′-AgMg. II. Single-Crystal Elastic Constants from 77° to 750°K

Abstract

The single-crystal adiabatic elastic constants of stoichiometric β′-AgMg have been determined from 77° to 750°K using the ultrasonic pulse-echo technique. The values obtained at 300°K are: c11=0.8380, c12=0.5635, c44=0.4755 (all in units of 1012 dyn/cm2). A relationship between the elastic constants and the lattice parameters of the two β′-structures AgMg and CuZn was found. A similarity of the temperature dependence of the elastic constants was also observed. From the extrapolated values of the elastic constants at 0°K, a Debye temperature of 287°K was obtained. Finally, using the elastic constant data, specific heat of β′-AgMg at constant volume was calculated and found to compare favorably with the classical value 3R at high temperature.