Oxygen and nitrogen effects on anelasticity and mechanical property of Ti35Zr30V10Nb25 multi-principal element alloys

The defect relaxation behavior of O/N-doped Ti35Zr30V10Nb25 multi-principal element alloys (MPEAs) were investigated using internal friction (IF) analysis and density functional theory calculations. A key distinction between O and N additions is that O addition induces two IF peaks (PO1 and PO2), while N addition results in only one IF peak (PN). PO1, PO2, and PN are attributed to O-Snoek-type relaxation in random solid solution (RSS) structure, O-Snoek-type relaxation in local chemical ordering structure, and N-Snoek-type relaxation in RSS structure, respectively. The IF analysis reveals that O addition leads to the formation of ordered O complexes, whereas ordered N complexes are not observed in the N-doped MPEAs. This contrast leads to the N-doped MPEAs exhibiting lower ductility and a weaker strain-hardening capacity compared to the O-doped MPEAs. This work demonstrates that the research into defect relaxation behavior has significant reference value for designing high strength-ductility MPEAs.