The formation of cellular precipitate and its effect on the tensile properties of a precipitation strengthened high entropy alloy

In this work, a precipitation strengthened high entropy alloy was subjected to thermo-mechanical process in order to homogenize the grain microstructure. Tensile tests from room temperature to 1000 °C were conducted; microstructures were observed by scanning electron microscope and transmission electron microscope. Formation of cellular precipitate along grain boundaries was observed and could be related to hot tensile ductility drop at 750 °C (1023 K). Experimental analysis has indicated that driving force for the formation of cellular precipitates could be resulted from the chemical instability of supersaturation after annealing and migration of grain boundaries, and this phenomenon could be suppressed either through alloy design to increase gamma-prime solvus, and to hinder the migration of grain boundaries. This study serves as a guideline to design composition and thermo-mechanical process for precipitation strengthened high entropy alloys.