Non-monotonic aging temperature dependence of superelasticity of Ti ₇₂Nb₁₅Zr₁₀Al₃ quaternary alloys

The influence of aging on the superelastic behavior of Ti ₇₂Nb₁₅Zr₁₀Al₃ alloy (which is associated with the martensitic transformation from β to α″ martensite) was investigated. The precipitation of ω phase during aging significantly affects the mechanical properties. A non-monotonic change in the stress required for martensitic transformation was observed as the aging temperature changed from 453 to 603 K. This variation in stress may be attributed to two factors: change of chemical composition in the matrix and internal strain because of ω phase formation. The likely variation in the stress for martensitic transformation associated with each of these effects was estimated. As the volume fraction of ω phase increased, the change in the chemical composition produced a greater effect than the change in the internal strain.