Role of fine nano-scaled isothermal omega phase on the mechanical and superelastic properties of a high Zr-containing Ti-Zr-Nb-Sn shape memory alloy

This work studied the microstructure, superelastic and mechanical performances of a high Zr-containing Ti-40Zr-8Nb-2Sn (at.%) shape memory alloy aged at 300 degrees C for 1 h. Nanodomains and quite fine nanoscaled omega(iso) phases with 2.1-2.9 nm wide and 2.9-4.4 nm long were formed in the aged alloy. The aged alloy in this study exhibited excellent superelasticity with a large total recovery strain of 7.1%, high ductility of 11.6% and high yield stress of 578 MPa, indicating that a good balance of functional and mechanical properties was achieved in the aged alloy. The stress-induced beta -> alpha '' martensitic transformation occurred in the nanodomain-containing aged Ti-40Zr-8Nb-2Sn alloy.