Effect of Heat Treatment Combined with an Alternating Magnetic Field on Microstructure and Mechanical Properties of a Ni-Based Superalloy

The effect of a two-step heat treatment including solution and aging heat treatments in an alternating magnetic field (AMF) on microstructure and mechanical properties of the Ni-based superalloy DZ483 was investigated. In the solution heat treatment, the AMF significantly reduced the chemical segregation. In the aging heat treatment, the application of the AMF was found to not only modify the partition ratios of some elements like Al and Ti between the γ' precipitate and the γ matrix, but also to distinctly accelerate coarsening of γ' precipitates and to result in a larger mean particle size. Additionally, the morphology of γ' precipitates gradually evolved from a quasi cube without an AMF to a regular cubic shape in the AMF. Mechanical performance tests showed that hardness and tensile strength of the samples heat treated in the AMF were increased in comparison with those without an AMF. It is shown that the enhanced diffusivity in the AMF is mainly responsible for the change in microsegregation, particle size, and morphology evolution. Furthermore, the AMF promotes the solid solution strengthening and the order strengthening, both of which contribute to the improvement of mechanical properties.