Microstructure evolution and mechanical properties of a Fe, Cr-rich multiphase Ni3Al-based superalloy during transient liquid phase bonding process

In this paper, a Fe, Cr-rich multiphase Ni3Al-based alloy is joined through transient liquid phase bonding (TLP) technique. Different from typical γ+γ′ dual phase Ni3Al-based alloys, the joint can be divided into three distinct zones: isothermal solidification zone (ISZ), gamma prime zone (GPZ) and diffusion affected zone (DAZ). Interestingly, the massive fine grains with γ+γ′ dual phase are observed inside the ISZ, and the GPZ consists of blocky γ′ phase. The precipitation of Cr-rich borides in DAZ provides an advantageous compositional condition for the local coarsening of γ′ phase. In addition, hardness value of the bonded samples fluctuates from the centerline to the BM and reaches the peak at the DAZ. The bonded specimens share equivalent room-temperature tensile strength and elongation to failure with the parent metal after the weld thermal cycle. Moreover, the fracture path propagates along the base metal (BM), which indicates excellent tensile properties of the joint.