Temperature-dependent plastic deformation of a refractory Al7.5(NbTiZr)92.5 medium-entropy alloy with a bcc+B2 structure

Abstract

Non-refractory elements, like Al, can enhance both room-temperature tensile strength and ductility of refractory high/medium alloys (RH/MEAs) due to the formation of ordered nanodomains changing the dislocation glide character. To elucidate their influence at higher temperatures, we reported here the tensile behaviour and microstructure response of a Al7.5(NbTiZr)92.5 (at.%) RMEA having a bcc (body-centred cubic) matrix with embedded B2 (ordered bcc) nanodomains at 298–1073 K, and compared the results obtained with those of a bcc NbTiZr alloy. Detailed analysis showed that profuse B2 nanodomains confined the dislocation motion in localised bands at T < 873 K, intensified the Portevin-Le Chatelier effect at 473 and 673 K, and enhanced the strength by ∼ 20–30 % at T ≤ 873 K, while losing the strengthening ability at 1073 K. These results manifest that ordered nanodomains originating from the non-refractory alloying can improve the medium-to-high temperature mechanical performance of RH/MEAs.