Residual thermal stresses in MoSi2-Mo5Si3 in-situ composites

Residual thermal stresses in MoSi2-Mo5Si3 in-situ composites are calculated for a dilute concentration of particles of one phase embedded in a matrix of the other, using the fields of anisotropic ellipsoidal inclusions. Addit ionally, the eutectic interfaces are modeled as boundaries between two anis otropic half-spaces. The misorientation between MoSi2-Mo5Si3 is obtained fr om the literature for Mo5Si3 precipitates in MoSi2 and by electron diffract ion in the scanning electron microscope (SEM) for the opposite case. Tensil e stresses of up to 3 GPa can develop after cooling from the eutectic tempe rature due to the thermal expansion mismatch between the phases. Electron m icroscopy of are-melted Si-rich Mo,Si, shows that stresses are relieved by intergranular fracture in Mo5Si3 and either dislocation plasticity or trans granular cracks in MoSi2, in a manner consistent with the calculations. (C) 1999 Elsevier Science S.A. All rights reserved.