Effect of heat treatment on microstructures and tensile properties of Ni-base superalloy M963

The effect of solution treatment (ST) on tensile properties of M963 Ni-base superalloy tested at 800 °C has been investigated. The detailed microstructures, fracture surfaces and dislocation structures are examined through energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). With increasing solution treated temperature, the yield strength (YS) and ultimate tensile strength (UTS) increase, however, the elongation decreases. Microstructural observations show that the morphologies of carbide, primary γ′ and re-precipitated γ′ change significantly with increasing solution treated temperature. The main deformation mode is γ′ by-pass when solution treated temperature is lower than 1220 °C, and changes to γ′ shearing at 1230 °C. The interface of carbide with matrix is the main site of crack initiation and propagation under all testing conditions.