Residual thermal stresses in MoSi2-Mo5Si3 in-situ composites

Abstract

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. Additionally, the eutectic interfaces are modeled as boundaries between two anisotropic half-spaces. The misorientation between MoSi2-Mo5Si3 is obtained from the literature for Mo5Si3 precipitates in MoSi2 and by electron diffraction in the scanning electron microscope (SEM) for the opposite case. Tensile stresses of up to 3 GPa can develop after cooling from the eutectic temperature due to the thermal expansion mismatch between the phases. Electron microscopy of arc-melted Si-rich Mo5Si3 shows that stresses are relieved by intergranular fracture in Mo5Si3 and either dislocation plasticity or transgranular cracks in MoSi2, in a manner consistent with the calculations. © 1999 Elsevier Science S.A.