A metastable Ti–Zr–Nb–Al multi-principal-element alloy with high tensile strength and ductility

How to improve the plasticity of body-centered cubic (BCC) multi-principal element alloys (MPEAs) is still a challenging task. Inspired by the strategies of transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP), different amount of Al is added to Ti58Zr34Nb8 base alloy to tailor the mechanical property. It is revealed that the resultant Ti52Zr34Nb8Al6 alloy has an extraordinary tensile strain of 35%, while maintaining a high yield strength of 810 MPa and an ultimate tensile strength of 962 MPa. Microstructural investigations indicate that the excellent comprehensive mechanical properties can be ascribed to the stress-induced martensite transformation (SIMT) and subsequent hierarchical deformation twinning activated in the SIM. This study not merely provides a low-density structural material with outstanding strength-toughness combination, but also opens a window for developing novel alloys with attractive mechanical properties.