Microstructure and Tensile Properties of New Ni₃Al Based Single Crystal Superalloy

A new Ni₃Al based single crystal superalloy was prepared by liquid metal cooling (LMC) method and treated by 1 290 ℃×4 h solid solution and 1 000 ℃×4 h aging. The microstructure and tensile properties at different temperatures (23-900 ℃) of the alloy were studied. The results show that the γ' phase in the test alloy structure showed a regular cube shape after solid solution and aging treatment, whose average size was about 0.55 μm and volume fraction was about 72%. The tensile strength and yield strength of the alloy increased first and then decreased with increasing temperature, reaching the peak values at 800 ℃, which was 856 MPa and 808 MPa, respectively. The change of elongation after fracture with temperature was opposite to that of strength; the elongation after fracture reached a minimum value of 11% at 800 ℃. The fracture mode of the alloy was pure shear fracture when stretched at 600 ℃ and below. When stretched at 760 ℃, the alloy had a mixed fracture of pure shear fracture and microporous aggregation. When the tensile temperature was between 800-900 ℃, the alloy fractured in a microporous aggregation fracture mode.