Influence of an oxygen-enriched layer on the tensile properties of an alpha titanium alloy

Abstract

The manuscript focuses on establishing the role of an oxygen-enriched layer (OEL) on the tensile properties of an alpha titanium alloy, Ti-Al-Zr. The samples were heat-treated in the inert and air atmosphere for different durations up to 700 h. The air oxidation led to the formation of the OEL near the surface of the specimen. The specimens were characterized by different metallurgical techniques like a stereo microscope, optical microscopy, micro-hardness measurement and grain size measurement. The oxygen profiling was done by the glow discharge optical emission spectroscopy technique. The tensile testing was done at room temperature at a strain rate of 2.5 × 10−4 s−1. The fracture surface was examined under scanning electron microscopy. The tensile properties-yield strength and ultimate tensile strength were in the same range for the specimens oxidized in the inert and air atmosphere. However, the specimens oxidized in the air atmosphere showed a drastic decrease in ductility with increasing oxidation duration. The entire specimens oxidized in the inert atmosphere showed dimples features, typical of a ductile failure. The specimens oxidized in the air atmosphere showed fracture features like intercrystalline fracture, slip bands and cleavage facets in addition to dimples features. The OEL showed brittle failure and the regions other than OEL showed ductile failure. The role of oxygen on the tensile properties and the development of different fracture features during air oxidation are discussed.