Deformation mechanisms in MoSi2 at temperatures above the brittle-to-ductile transition temperature .1. Polycrystalline MoSi2

The deformation mechanisms above the brittle-to-ductile transition temperature in polycrystalline samples of MoSi2 have been studied. Thus samples have been deformed at 1200, 1400 and 1600 degrees C respectively at a series of strain rates, ranging from 10(-2) to 10(-5) s(-1). Thin foils have been cut from the deformed samples and diffraction contrast experiments have been performed to determine the identity of the dislocations in the deformed microstructure. Crystallographic analyses have been carried out to determine the line direction of defects, and this information, taken together with a knowledge of the Burgers vectors, has been used to assess the degree that slip and climb have occurred during deformation. The microstructural evidence is consistent with glide occurring during deformation at 1200 degrees C at all strain rates, whereas at 1400 degrees C there appears to be an increasing contribution from climb as the strain rate is reduced. At 1600 degrees C, climb appears to be the dominant deformation mechanism at all strain rates. Diffusion data deduced on the basis of the microstructural observations are consistent with other estimates of diffusion coefficients determined for MoSi2.