Effect of oxygen boost diffusion treatment on the mechanical properties of Ti-6Al-4V alloy

In this present paper, the effect of oxygen boost diffusion (OBD) treatment on the mechanical properties of Ti-6Al-4V alloy has been studied. Optical microscopy (OM) and X-ray diffractometry (XRD) were employed to characterize microstructure and phase character. Uniaxial tension tests were performed to study the mechanical properties. Test results showed that after oxygen boost diffusion treatment, a hardened layer of ≈ 150 μm in depth formed on the surface of Ti-6Al-4V alloy, and the surface hardness reached ≈ 950HV, which is twice as high as that of the substrate. However, the yield strength, tensile strength and elongation after OBD treatment decreased by about 16%, 13% and 35% respectively. The reasons for the decrease in mechanical properties are as follows: 1. The high temperature during the process of OBD treatment resulting in the growth of grains; 2. Brittle cracking of surface oxygen strengthened layer at low strain.