Excellent mechanical properties and thermal stability in a Zr gettering treated (VNb)₈₀(TaTi)₂₀ refractory multi-principal element alloy

Refractory multi-principal element alloys (RMPEAs) have garnered attention due to their high strength at elevated temperatures. However, their insufficient uniform elongation and thermal stability hinder their practical application. In this work, a single-phase BCC-structured (VNb)₈₀(TaTi)₂₀ RMPEA is designed based on the considerations of mixing enthalpy and Labusch solid solution strengthening model, which exhibits a tensile strength over 900 MPa and uniform elongation of ∼19 %. Unfortunately, the alloys containing high-concentration interstitial impurities (e.g. 300 wppm O, HO-alloy) suffer from severe embrittlement during long-term thermal aging, mainly due to the formation of Ti-(C/N/O) precipitates. By applying the Zr-foil gettering treatment, the concentration of interstitial impurities can be reduced below 100 ppm (LO-alloy), which greatly enhances thermal stability. The LO-alloy can maintain the microstructural stability and mechanical properties under thermal aging at 900 and 1000 °C for at least 1000 h. In addition to the desired combination of strength and ductility at room temperature, the alloy holds a high specific tensile strength of 98.9 MPa cm³/g at 1000 °C, which further grants it strong application potential at elevated temperatures. During tensile deformation, twinning is observed at room temperature, which is believed to enhance both strength and ductility.