Effect of temperature and cyclic loading on stress relaxation behavior of Ti–6Al–4V titanium alloy.

The effect of temperature and cyclic loading on stress relaxation (SR) behavior of Ti–6Al–4V titanium alloy was studied by uniaxial tensile test. SR limit and rate vary with increasing the temperature and cyclic loading times. The microstructural variations were observed by scanning and transmission electron microscopes. Unstable SR behavior happens at 450–550 °C, which becomes obvious with the increase of cyclic loading times or the decrease of relaxation temperature. The stress instability maybe attributes to the activation energy improvement. Based on dislocation distribution and morphology as well as stress exponent values varying from 1.8 to 2.4, SR mechanism of the alloy is dislocation creep in the tested temperature range. The mechanical properties of the alloy at room temperature almost maintains invariable after SR process. However, the discontinuous yielding in as-received alloy changes to continuous yielding in relaxed ones. [ABSTRACT FROM AUTHOR]