Tensile Property of Electrochemically Polished Titanium Alloy

Tensile tests of titanium alloy (Ti-6Al-4V) with different thickness of 0.4 mm and 0.3 mm, were performed to investigate thickness dependency of superplasticity. To keep the same inner microstructure between specimens with different thicknesses, electrochemical polishing method was applied to reduce thickness. By keeping the voltage for the electrochemical polishing as 30 V the thickness decreased as linear with respect to polishing time. Further, tensile tests of 0.4 mm with strain rate 9.3.10(-4) sec(-1) were conducted at room temperature and 850 degrees C. And the superplasticity of 450 % elongation was obtained at 850 degrees C. For quantitative measurement of superplasticity, strain rate sensitivity (m value) was calculated from the tensile test by changing strain rate. The m values of the unpolished 0.4 mm specimen and the polished 0.3 mm specimen were 0.52 and 0.43, respectively. Strain rates to calculate the m value were 5 .10(-4) sec(-1) and 1 . 10(-3) sec(-1). Consequently the reduction of thickness resulted in the reduction of m value, which means less superplasticity for thinner sheets of Ti-6Al-4V.