Microprocesses of the deformation of single and polycrystalline

MoSi2 single crystals in the soft 201 orientation and polycrystals were deformed in constant strain rate tests in compression between 300 and 1200°C for single crystals, and between 495 and 1250°C for polycrystals. Stress relaxation and temperature change tests were performed to determine the activation parameters of the deformation. In addition to conventional transmission electron microscopy in a high-voltage electron microscope, in situ straining experiments were carried out in this instrument to observe the deformation processes directly. A new model is proposed to interpret the flow stress anomaly in MoSi2 single crystals. In polycrystals, the deformation is controlled by dislocation glide below about 1050°C, however, by decohesion of a grain boundary phase above this temperature. © 2001 Elsevier Science B.V. All rights reserved