ELEVATED TEMPERATURE OXIDATION OF BORON MODIFIED Ti-6Al-4V

by Sweeney, Deborah May-Katherine

The addition of trace amounts (~0.1 wt%) of boron to titanium alloys refines the as-cast grain size by an order of magnitude from 2000?m to 200?m. The reduced grain size has potentially beneficial effects on the processibility of titanium alloys. Reports also indicate that the room temperature corrosion resistance of the boron containing alloys may be substantially greater than conventional titanium alloys. In this study, the effects of boron addition on oxidation resistance are investigated, since conventional titanium alloys have limited corrosion resistance in air above 650°C. The mass gain per unit surface area was measured during elevated temperatures exposed to air to compare the oxidation of the alpha-beta titanium alloy, Ti-6Al-4V with boron and without boron additions. These findings are presented in conjunction with the characterization of boron modified titanium alloys. Results include weight gain as a function of time and temperature, activation energy calculation, microstructural characterization of the oxide layer, measurement of oxide scale thickness and composition profiles. The experimental results are compared to literature values for similar experiments on conventional titanium alloys.