Elasticity of Mo-Re and W-Re alloys under hydrostatic pressure

The elastic moduli of single crystals of Mo-16%Re, Mo-29% Re, and W-11% Re have been measured to 0.5 GPa (5 kbar) hydrostatic pressure at room temperature. The composition dependence of the pressure derivatives of the moduli follows the trends established for Nb-Mo and Ta-W alloys. This finding was unexpected since the shear modulus, C′ = (C11−C12)/2 has a sharp peak in its composition dependence at e/a = 6.0. The results are explained in terms of the differing effects of compression on different d-electron subbands. Because dC′/dP decreases with increasing Re content, it is also suggested that the compositional range for stability of the bcc structure decreases with increasing pressure.