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. 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.