Effect of temperature and hold time on internal hardening behavior of a near α titanium alloy under cyclic deformation

In the present work, the study of dynamic strain aging (DSA) in near α titanium alloy Timetal 834 is reported in terms of internal hardening variables (kinematic and isotropic hardening variable). Total strain controlled low cycle fatigue tests have been conducted in air at 300 °C and from 400 °C to 500 °C at a temperature interval of 25 °C at nominal strain rates of 6.67 × 10−3 s−1. The alloy exhibits gradual cyclic softening till failure at 300 °C, whereas, it exhibits initial cyclic softening followed by marked cyclic hardening from 400 °C to 500 °C. The cyclic hardening is attributed to DSA phenomena, resulting due to increase in isotropic stress component. The observed maximum peak stress ratio, lower fatigue life and minimum half-life plastic strain range at 450 °C indicates the maximum effect of DSA at that temperature. The fatigue life of tensile and compressive hold at 450 °C was observed to be inferior as compared to pure fatigue tests.