Abstract:In this paper, a Ni-28.5Al-43V (at%) hypereutectic alloy was prepared by liquid metal cooling technology (LMC), The microstructure evolution and mechanical properties of the alloy were investigated by optical microscopy (OM), scanning electron microscopy (SEM) and three-point bending (3PB) test. Under the experimental conditions(Temperature gradient GL=310K/cm, Growth rate V=6～150μm/s), the results show that the steady-state growth microstructure of NiAl-43V is composed of primary V dendrites and eutectic structure (NiAl lamellar +V lamellar). 3PB test shows that the maximum room temperature fracture toughness(RTFT) of NiAl-43V hypereutectic alloy is four times higher than that of NiAl alloy.The RTFT decreases from 22.679 MPa.m 1/2 at 6 μm/s to 18.422 MPa.m 1/2 at 150 μm/s as the growth rate increases.The reason is that the fine-grained strengthening effect caused by the increase of growth rate is weaker than the adverse effect of increased primary V dendrites and inter-cell regions on fracture toughness. Fracture morphology analysis of alloys indicates that alloy fracture is quasi-cleavage fracture.Crack blunting, crack renucleation, crack deflection, interfacial debonding, crack bridging and linkage of microcrack toughening mechanism contribute to the improvement of room temperature fracture toughness of NiAl-43V alloy in crack propagation. The precipitation of primary V dendrites reduces the fracture toughness of the alloy.