Effects of solution treatment and cold rolling on structure and tensile properties of hot-rolled Ti–7.5Mo alloy

Abstract

The effects of solution treatment (ST) and cold rolling (CR) on structure and tensile properties of a heavily hot-rolled (HR) Ti–7.5Mo alloy were investigated. Experimental results indicated that, after HR with a one-pass 65% reduction in thickness, the pores in as-received samples substantially disappeared, the misorientation angle distribution became broader, and grain texture shifted toward $\left\langle {10\bar{1}0} \right\rangle$. Post-HR ST produced an orthorhombic α″-phase with fine needle-type morphology and caused misorientation to narrow down to 55°–65° with substantially random texture; post-ST CR caused misorientation shift toward high-angle side and texture toward $\left\langle {10\bar{1}0} \right\rangle$ and $\left\langle {2\bar{1} \bar{1}0} \right\rangle$. With an increase in reduction in thickness, α′(102) intensity increased at the expense of two adjacent (112)/(022) α′′-peaks. All X-ray diffraction, metallography and electron backscattered diffraction on scanning electron microscope results indicated that pre-ST HR did not affect the formation of the desired low-modulus α′′-phase when the alloy was subsequently solution-treated. From a practical point of view, the most optimal tensile properties may be found in the sample solution-treated at 900 °C for 30 min and cold-rolled by a 20% reduction in thickness, which demonstrated a yield strength of 924 MPa, an ultimate tensile strength of 933 MPa, a tensile modulus of 73 GPa, and an elongation of 26%.