HIGH-TEMPERATURE PLASTIC ANISOTROPY IN MOSI2 SINGLE-CRYSTALS

The temperature dependence of the 0.2% yield stress in MoSi2 single cr ystals has been determined from 900 to 1600 degrees C for three specim en orientations, [001], [021] and [771]. Four different slip systems h ave been identified: {013}[100], {011}[100], {1(1) over bar0$}1/2[111] and {0(1) over bar3$}1/2[331]; the critical resolved shear stresses ( CRSS) of these systems differ significantly from one another. MoSi2 is especially strong in the [001] orientation at temperatures above 1100 degrees C, because decomposition of 1/2(331) dislocations forces slip on a fifth system, either {12(3) over bar}1/2[111] or {0(1) over bar1 $}1/2[111]. The CRSS of each slip system is discussed in terms of the influence of the dislocation core structure on the Peierls stress.