Deformation mechanisms and effect of oxygen addition on mechanical properties of Ti-7.5Mo alloy with α” martensite

Abstract

Effect of oxygen content as an important interstitial solute on the microstructure and mechanical properties of Ti-7.5Mo alloy was investigated. With increasing the oxygen content, the yielding strength, ultimate tensile strength and Young’s modulus of Ti-7.5Mo-xO (x=0, 0.2, 0.3, 0.4, 0.5) alloys increased, while the elongation showing a decreasing tendency. Solid-solution strengthening by the oxygen atoms has been addressed as the main strengthening mechanism. Ti-7.5Mo-xO (x ≤ 0.3) alloys have been regarded with an excellent combination of high yield strength (~640 MPa) and elongation (~28%), as well as low Young’s modulus (~60 GPa). The deformation microstructure of orthorhombic-α” martensite in Ti-7.5Mo alloy was also investigated by tracking a change in the microstructure of a selected area upon tensile deformation. Deformation twins induced by 5% tensile straining was identified as {112}α”-type I twins, which had not been reported before in α”martensite in β-Ti alloys.

Keywords

• β-titanium alloys
• biomaterials
• orthorhombic-α” martensite
• oxygen
• deformation twinning