Microstructure and Tensile Properties of Ultrafine-Grained Ni-Based Alloy Prepared by Severe Deformation Rolling

Ultrafine-grained Ni-based alloy was prepared by 98% severe deformation with combination of asymmetric-rolling and symmetric-rolling. The microstructure and tensile properties of the alloy after annealing were studied. The results show that the structure of Ni-based alloy was significantly refined after rolling and the grain size was less than 200 nm and 300 nm after annealing at 700℃ and 800℃, respectively. It was found that the ultrafine-grained Ni-based alloy had a good structure stability. The strength of Ni-based alloy was significantly improved after rolling and remained very high after annealing at 700℃ and 800℃. Especially after annealing at 700℃, the yield strength and tensile strength were increased from 243 MPa and 679 MPa to 1 907 MPa and 1 949 MPa, respectively. The strength improvement and good structure stability of ultrafine grain Ni-based alloy were mainly attributed to a large amount of uniformly dispersed nano-sized γ' phase that precipitated during annealing process.