Refractory multi-principal element alloys MoxNbTiZry: Microstructure, mechanical properties and oxidation resistance

Abstract

Microstructures and properties of the Mo_xNbTiZr_y refractory multi-principal element alloys (RMPEAs) are investigated. The results show that the single-phase solid solution forms in the heat-treated Mo_xNbTiZr_y alloys with x/y ≤ 0.6, while the thermally stable Zr-rich phase is separate from the (Mo, Nb)-rich phase with x/y ≥ 1. The room temperature strength of the Mo_xNbTiZr_y alloys is mainly derived from the solid solution strengthening of Mo and Zr atoms. The high temperature strength increases with the larger negative mixing enthalpy and the higher melting temperatures for the Mo_xNbTiZr_y alloys as well as other bcc solid solution RMPEAs. Dynamic recrystallization is more sluggish in MoNbTiZr_0.2 alloy compressed at 1200 °C. A phenomenological parameter δGb/γ is proposed to effectively estimate the ductility at room temperature for the Mo_xNbTiZr_y alloys and also other bcc solid solution RMPEAs. The formation of tortuous dislocations and abundant dislocation loops contributes to the better ductility of the Mo_xNbTiZr_y alloys with a lower Mo content. Moreover, oxidation resistance at 1200 °C has also been discussed for the Mo_xNbTiZr_y alloys.