Lattice strains in gold and rhenium under nonhydrostatic compression to 37GPa

Using energy-dispersive x-ray diffraction techniques together with the theo ry describing lattice strains under nonhydrostatic compression, the behavio r of a layered sample of gold and rhenium has been studied at pressures of 14-37 GPa. For gold, the uniaxial stress component t is consistent with ear lier studies and can be described by t = 0.06 + 0.015P where P is the press ure in GPa. The estimated single-crystal elastic moduli are in reasonable a greement with trends based on extrapolated low-pressure data. The degree of elastic anisotropy increases as alpha, the parameter which characterizes s tress-strain continuity across grain boundaries, is reduced from 1.0 to 0.5 . For rhenium, the apparent equation of state has been shown to be strongly influenced by nonhydrostatic compression, as evidenced by its dependence o n-the angle psi between the diffracting plane normal and the stress axis. T he bulk modulus obtained by inversion of nonhydrostatic compression data ca n differ by nearly a factor of 2 at angles of 0 degrees and 90 degrees. On the other hand; by a proper choice of psi, d spacings corresponding to quas ihydrostatic compression can be obtained from data obtained under highly no nhydrostatic Conditions. The uniaxial stress in rhenium over the pressure r ange from 14-37 GPa can be described by t = 2.5 + 0.09P. The large discrepa ncy between x-ray elastic:moduli and-ultrasonic data and theoretical calcul ations indicates that additional factors such as texturing or orientation d ependence of t need to be incorporated to more fully describe the strain di stribution in hexagonal-close-packed metals. [S0163-1829(99)02845-5].