Improvements in nonlinear elasticity and strength by grain refinement in a titanium alloy with high oxygen content

This paper reports an ultrafine-grained Ti–24Nb–4Zr–8Sn–0.4O (wt.%) alloy produced by warm rolling at 673 K, showing notable nonlinear elastic deformation with a recoverable strain of ∼3% as well as a tensile strength of 1200 MPa, Young’s modulus of 56 GPa and elongation of 8%. A duplex microstructure with nanosized α precipitates in ultrafine-grained β matrix was obtained by a subsequent three-step heat treatment to achieve a tensile strength of 1700 MPa, a fatigue strength of 1050 MPa and an elongation of 5%.

Research highlights
► The Hot forged Ti2448–0.4O alloy has weak nonlinear elastic deformation behavior.
► Its microstructure can be refined to the ultra-fine scale by warm rolling at 673 K.
► This improves the tensile strength to ∼1200 MPa and the recoverable strain to ∼3%.
► The heat treatments produce a duplex microstructure with the nano-sized a phase.
► This reaches tensile strength 1700 MPa, fatigue strength 1050 MPa and elongation 5%.