Superlative room temperature and cryogenic tensile properties of nanostructured CoCrFeNi medium-entropy alloy fabricated by powder high-pressure torsion

Abstract

Attaining decent tensile properties in materials fabricated by conventional powder metallurgy (PM) techniques has perennially been a pivotal challenge due to structural defects— typically pores. This work fabricates a nanostructured CoCrFeNi medium-entropy alloy with an uttermost relative density of 99.63% through PM, i.e., cold powder consolidation using high-pressure torsion followed by annealing. The cold-consolidated sample showed outstanding tensile strengths of 2.06 GPa and 2.81 GPa at room and cryogenic temperatures, respectively, which was never achieved in PM-processed materials. The enhanced cryogenic tensile properties can be associated with intensive mechanical twin activities. Additionally, engineering the microstructure through subsequent annealing leads to a desirable synergy of tensile strength and ductility, which are highly sought after in structural applications. The present findings pave the way to fabricate the parts with superior tensile properties for cryogenic applications through a PM-based approach.