Influences of laser remelting treatments on microstructure and tensile properties of multiphase Ni3Al-based intermetallic alloy

The microstructure control of multiphase Ni3Al-based intermetallic alloy by traditional heat treatment is still limited, especially size and volume fraction of interdendritic beta phase cannot be effectively reduced, due to the limitation of interdendritic beta phase dissolution temperature close to the melting point of the alloy. In present work, the temperature gradient and solidification rate of the alloy under different laser remelting parameters were calculated by the Rosenthal equation. Afterward, the as-cast multiphase Ni3Al-based intermetallic alloy (19.4 vol% of interdendritic beta phase) was remelted under different laser parameters of 3000-4500 W laser power and 5-20 mm/s laser scanning rate. And the effects of different laser remelting parameters on the microstructure, room temperature, and 980 degrees C high-temperature tensile properties of multiphase Ni3Al-based intermetallic alloy were studied. The results show that laser remelting treatment with the appropriate parameters (4000 W laser power and 10 mm/s laser scanning rate) can effectively reduce the size and volume fraction of interdendritic beta phase and the morphology and size of gamma ' phase in the gamma '+gamma dendrite, and significantly refine the microstructure of alloy, thus effectively improving the room temperature and 980 degrees C tensile properties of multiphase Ni3Al-based intermetallic alloy. Under the optimum laser remelting parameters of 4000 W-10 mm/s, the tensile strength at room temperature and 980 degrees C of the corresponding laser remelting alloy can reach 1215 MPa and 280 MPa, respectively, and the elongations after fracture of the corresponding alloy are 14.09% and 6.41%, respectively.