Microstructure and mechanical properties of a Ni-based superalloy after heat treatment in a steady magnetic field

The effect of heat treatment with the aid of a steady magnetic field (SMF) on microstructure and mechanical properties of the superalloy DZ483 was investigated. The SMF was found to reduce the average size of γ′ precipitates and also to delay their splitting in the dendrite core, but had no pronounced effect on the morphology of the precipitates in the interdendritic region. Measurement of the distribution of alloying elements showed that the degree of microsegregation in the samples heat treated in the SMF was higher than in those without the SMF. It is concluded that the SMF reduced the diffusivity of the alloying elements and thus decreased the coarsening rate of the precipitates, which led to a reduction of their average size and a delay of their splitting. With respect to the mechanical properties it was found that the Vickers hardness and the tensile strength of the samples after heat treatment in the SMF increased. According to the precipitation hardening theory, the Orowan process is the dominating deformation mechanism in DZ483 at a high temperature and thus the DZ483 samples with a smaller size of γ′ precipitates after heat treatment in the SMF showed a better tensile performance.