Design and tensile properties of a bcc Ti-rich high-entropy alloy with transformation-induced plasticity

Abstract

A new bcc Ti-rich high-entropy alloy (HEA) of composition Ti35Zr27.5Hf27.5Nb5Ta5 was designed using the ‘d-electron alloy design’ approach. The tensile behavior displays a marked transformation-induced plasticity effect resulting in a high normalized work-hardening rate of 0.103 without loss of ductility when compared to the reference composition Ti20Zr20Hf20Nb20Ta20. In this paper, a detailed microstructural analysis was performed to understand the deformation process, revealing architectural-type microstructures and a high volume fraction (65%) of internally twinned stress-induced martensite α″ after mechanical testing. This study opens the way to mechanical properties optimization and enhancement of titanium-based HEAs by combining multiple alloying designs. IMPACT STATEMENT For the first time, proof is given that transformation-induced plasticity was triggered in a bcc refractory high-entropy alloy, leading to a twofold increase in the normalized work-hardening rate.