Spatiotemporal characteristics of Portevin-Le Chatelier effect in Ti-Mo alloys under thermo-mechanical loading

The Portevin-Le Chaterlier (PLC) effect in Ti-12Mo and Ti-15Mo alloys has been investigated by using uniaxial tensile tests in a temperature range of 25-350 °C with an applied strain rate of the order of 10−3 s−1, coupled with a digital image correlation (DIC) method. The experimental results show an increase of the yield stress from 25 °C to 250 °C followed by a decrease. Moreover, PLC effect occurs above 250 °C and stress drop magnitude increases while the number of stress drops per unit time decreases with increasing the strain and temperature as well as decreasing Mo contents. These macroscopic features are related to the reduced intensity of interactions between ω phase particles and mobile dislocations as decreasing temperature and increasing Mo contents. Furthermore, a relatively higher temperature and lower Mo content tend to weaken the spatial cohesion of propagation bands and strengthen strain localization, leading to a change of PLC bands from type A to type B and the increase of strain rate within the PLC bands, which are related to the increased precipitation of ω phases. Additionally, the elongation at fracture is significantly influenced by PLC effect in Ti-Mo alloys.