Cracking in Cr–Cr2Nb eutectic alloys due to thermal stresses

The microstructures of the Cr–Cr2Nb two-phase alloy as affected by thermal stresses have been investigated for three different systems: (1) Cr-rich particles surrounded by the eutectic network; (2) Cr2Nb particles embedded in the Cr-rich matrix; and (3) Cr-rich particles inside the Cr2Nb matrix. Micrographs of the as-cast and annealed specimens show that microcracks are primarily located at the interface between the particle and the matrix. These observations are related to the presence of thermal stress field of elastic inclusions with its maximum tensile and shear stresses located at the interface boundary. The theoretical analyses presented support the formation of crack embryos at the interface as the local tensile stress exceeds the critical value for crack nucleation.