An Experimental Method for Characterizing the Thermomechanical and Dynamic Deformation of a TWIP Titanium Alloy

Characterization of high-rate, thermomechanical behavior is critical to design and selection of materials for dynamic loading applications. Materials that exhibit twinning-induced plasticity (TWIP) are of particular interest to such applications, as they have been shown to provide improved toughness and ductility. This work is focused on the high-rate thermomechanical response of metastable, beta-phase Ti-15Mo (wt%), a TWIP-exclusive alloy. An experimental apparatus for measuring the dynamic behavior of materials subjected to strain rates on the order of 10² s^-1 and temperatures up to 500°C was developed in this work. This system is based on the traditional Kolsky (or split-Hopkinson pressure) bar design, with the addition of an external furnace and bar actuation system. A synchronized pneumatic actuation system is used to control the motion and timing of the incident and reflected bars to minimize the temperature gradient across the sample and avoid bar heating. The viability of the system is first illustrated by examining the combined high-temperature, high strain rate response of Ti-64. The rate sensitivity of metastable beta phase Ti-15Mo alloy subjected to strain-rate dependent compressive loading at ambient and elevated temperatures is then investigated in relation to the twin fraction.