HIGH-TEMPERATURE DEFORMATION OF MOSI2 SINGLE-CRYSTALS WITH THE C11B STRUCTURE

Single crystals of MoSi2 with the C11b structure have been deformed in compression at 900-1500°C. Slip of the {013}〈331〉- and/or the {013}〈331〉-type is activated depending on crystal orientation. The critical resolved shear stress (CRSS) for {013}〈331〉-slip is much higher than that for {013}〈331〉-slip. At about 1300°C where ductility is remarkably improved, 〈100〉- and 〈110〉-type ordinary dislocations are observed and the climb mobility of these dislocations is very high. The CRSS for {013}〈331〉-slip, which depends on orientation exhibits a slight anomalous peak at 1000-1100°C. The anomalous strengthening is interpreted by the cross-slip mechanism as similar to that in L12 ordered alloys. Ductility improvement of MoSi2 above about 1200°C is assisted by the formation of stacking fault which is closely related to the instability of the C11b against to the C40 structure. © 1990.