Osmium Metal Studied under High Pressure and Nonhydrostatic Stress

Interest in osmium as an ultra-incompressible material and as an analog for the behavior of iron at high pressure has inspired recent studies of its mechanical properties. We have measured elastic and plastic deformation of Os metal at high pressures using in situ high pressure x-ray diffraction in the radial geometry. We show that Os has the highest yield strength observed for any pure metal, supporting up to 10 GPa at a pressure of 26 GPa. Furthermore, our data indicate changes in the nonhydrostatic apparent $c/a$ ratio and clear lattice preferred orientation effects at pressures above 15 GPa.

Figure 1

$d$ spacing of the (110) diffraction peak as a function of $\psi$ and pressure. The data are shown as symbols; smooth curves show the $1–3{cos}^2\psi$ fits through each data set. The intersection of the dotted line with the curves shows the hydrostatic value of the $d$ spacing at each pressure step.

Figure 2

Pressure dependence of differential stress (top) and apparent $c/a$ ratio in maximum, minimum, and hydrostatic stress directions (bottom).

Figure 3

Evolution of the relative intensities for the Os (002) and (101) diffraction peaks.