Nonlinear elastic behavior induced by nano-scale α phase in β matrix of β-type Ti–25Nb–3Zr–2Sn–3Mo titanium alloy

• Nonlinear elastic behavior is induced by nano-scale α precipitate.
• Quantitive relation exists between Vα and elastic behavior.
• εmax-R of 2.25% with strength of 900 MPa corresponds to Vα of 10%.
• Mechanical stabilization of the alloy relates to nonlinearity of (α+β) microstructure.

Large scale nonlinear elastic deformation behavior is induced by moderate precipitation of nano-scale α phase for Ti–25Nb–3Zr–2Sn–3Mo alloy after a strategy of cold rolling and short-time aging. Quantitive relationships are established between volume fraction of α phase (Vα) and elastic modulus, strength as well as maximal recoverable strain (εmax-R), where the highest εmax-R of 2.25% with strength of 900 MPa corresponds to Vα of 10%. With the Vα increasing, the elastic behavior transforms from “double yielding” to nonlinear elasticity and then normal linearity. It is considered that the nonlinear elasticity of the studied (α+β) microstructure is probably related to “mechanical” stabilization of the alloy, i.e. a blocking effect of α phase on the lattice shear from body-centered cubic β phase to orthorhombic-α″ martensite.