Mechanical properties of tantalum under high pressure

We have studied the effect of high pressure, up to 93 GPa, on the yield strength of tantalum single crystals, deformed in a relatively low strain regime (plastic strain smaller than 21%) in a diamond anvil cell. The stress tensor in the sample was calculated by an analysis of its x-ray diffracted signal; the sample strain was determined by an interferrometric method. Even if no dramatic effect of the pressure on the yield stress has been observed, the values of the measured yield strength are higher than expected within the elastic theory of dislocations. This could be due to a coupled effect of pressure and plastic strain.