Cold deformation behavior of the Ti-15Mo-3Al-2.7Nb-0.2Si alloy and its effect on α precipitation and tensile properties in aging treatment

The microstructure and texture were investigated in cold-rolled Ti-15Mo-3Al-2.7Nb-0.2Si alloy with differing degrees of reduction. The texture of the alloy was prone to rotate to <110> orientation and more sub-boundaries were produced with the increase of the cold-deformation. Precipitation during aging was influenced by the dislocations, sub-boundaries and other defects formed in cold rolling, for they would provide assisted-nucleation sites and decrease the duration of β→α transformation. The α precipitates with the scale of 100-400 nm in the cold-rolled 20% plus aging sample, brought about the high-strength of 1612 MPa and the elongation of 6.5%. The highest strength of 1770 MPa was obtained in the cold-rolled 50% plus aging sample, which has little plastic deformation, due to the coarse α phase precipitated in sub-boundaries. The role of dislocations and sub-boundaries in influencing α precipitation and the tensile properties of Ti-15Mo-3Al-2.7Nb-0.2Si alloy are described in this paper.