Low-density nano-precipitation hardened Ni-based medium entropy alloy with excellent strength-ductility synergy

Abstract

The development of advanced structural materials with a synergistic combination of strength and ductility is currently one of the thrust areas of research for material scientists. An alloy design strategy for such materials takes into consideration the ease of processing, density reduction, and economic viability along with unprecedented mechanical properties. The present study reports a low-density, low-cost medium entropy alloy, designed based on the CALPHAD approach, for structural applications. The designed Ni-Fe-Cr-Al based alloy was cast, homogenized and cold rolled to 75% thickness reduction. The cold-rolled full hard material was isothermally annealed at 900°C for varying duration with a quest for an in-depth understanding of static recrystallization mechanisms. The specimens annealed at 900°C for varying durations were aged at 600°C for 5 h. Based on the systematic understanding of recrystallization and precipitation mechanisms involved, a suitable thermo-mechanical process route was judicially selected for the designed alloy, which contributed to an excellent combination of high tensile strength of > 1 GPa accompanied by an appreciable total elongation of > 50%. This superior strength-ductility synergy surpassed the strength-ductility combination of many existing medium and high entropy alloys and can be investigated further to assess its potential applications in challenging existing solid solution (SS) strengthened superalloys.