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The addition of reinforcements provides an effective way to achieving high-performance nickel matrix composites. In this study, Inconel 718 alloys have been manufactured by laser powder bed fusion (LPBF) and Re/Inconel 718 composites were prepared by adding rhenium (Re) elements. The effects of two heat treatment processes (1020 °C and 1140 °C for 2 h) on the microstructure evolution, mechanical properties and corrosion resistance of the Re/Inconel 718 composites were investigated. Results reveal that the added Re element effectively inhibits the continuous growth of columnar crystals and promotes the formation of a limited fraction of fine, uniform equiaxed grains. At a solution temperature of 1020 °C, the specimen undergoes partial recrystallization accompanied by abundant fine reinforcing phases along grain boundaries. While this reduces texture strength, the proportion of low-angle grain boundaries is not reduced. When the solution temperature is 1140 °C, complete recrystallization occurs in the specimen and large-size reinforcing phases precipitate, accompanied by grain growth and formation of annealing twins. Concurrently, texture strength disappears and shows random grain orientation, while grain boundary migration converts numerous low-angle grain boundaries to large-angle grain boundaries. The diffusion behavior of the Re element in the alloy becomes increasingly enhanced with elevated solution temperature. When the solution temperature is 1020 °C, optimal overall properties of the alloy are optimized. The elimination of residual stresses, dissolution of Laves phases, homogenization of the microstructure and precipitation of fine reinforcing phases are responsible for the enhanced comprehensive performance of the alloys. • The added Re element inhibits the continuous growth of columnar crystals and promotes the formation of equiaxed grains. • The mechanical properties and corrosion resistance of the Inconel 718 alloys are improved. • The diffusion behavior of the Re element in the alloy becomes increasingly enhanced with elevated solution temperature. • The heat treatment temperature of 1020 °C yields optimal overall properties in the Re/Inconel 718 composites.
Bai et al. (Thu,) studied this question.