Ageing behavior of Ti–6Cr–3Sn β titanium alloy

In this study, the effect of ageing treatment on mechanical, shape memory and pseudoelastic properties of our recently developed metastable β Ti–6Cr–3Sn alloy was investigated for engineering applications. Solution-treated Ti–6Cr–3Sn alloy was aged at 373 K, 473 K, 573 K and 673 K using vacuum-sealed quartz tubes for 3.6 ks followed by water quenching. Shape memory effect, fracture strain and hardness were improved by ageing at 373 K most probably due to fine scale isothermal omega (ω) phase precipitation. However for samples aged at 473 K, 573 K and 673 K, fracture strain (2%, 2% and 4%, respectively) was drastically reduced, yield stress (440 MPa, 580 MPa and 490 MPa, respectively) and hardness (HV329, HV450 and HV457, respectively) were drastically increased as compared to solution-treated and aged at 373 K conditions with no pseudoelastic response. This brittle behavior was due to increase in the amount of isothermal ω phase precipitation as compared to 373 K ageing conditions. It is concluded that Ti–6Cr–3Sn alloy in solution-treated and aged at 373 K has potential as shape memory and pseudoelastic materials applications with excellent strength–ductility correspondence. However mechanical, shape memory and pseudoelastic properties were drastically deteriorated by ageing at 473 K, 573 K and 673 K due to increase in the amount of isothermal omega (ω) phase precipitation as compared to 373 K ageing conditions.