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.