Monday  |  Salon 9  |  05:30 PM–05:50 PM

#15766, Thermomechanical Characterization and Dynamic Compression of the TWIP Alloy Ti-15Mo (wt.%)

The mechanical behavior of metallic alloys subjected to high strain-rate loading can vary significantly from the behaviors exhibited at quasi-static or intermediate strain rates, necessitating high strain-rate characterization for dynamic applications. Strain rates on the order of 102 s-1 to greater than 104 s-1 commonly occur in dynamic events, including armor and armor defeat systems, bird strike and foreign object damage in jet turbines, satellite protection, high-speed forming of parts, and automotive crash testing. Additionally, structural alloys in dynamic loading applications are often subjected to elevated temperatures, which may impact the resulting mechanical behavior. As such, understanding the combined effects of high strain-rates and temperatures is critical to the design and selection of structural alloys for dynamic loading applications. Alloys that exhibit transformation-induced plasticity (TRIP) and/or twinning-induced plasticity (TWIP) have been shown to provide improved toughness and ductility, lending them to dynamic loading applications. This work investigates the high strain-rate thermomechanical response of the metastable beta-phase in Ti-15Mo (wt.%), a TWIP-exclusive alloy. The aim of this study is to quantify the strain-rate sensitivity under quasi-static and dynamic compressive loading at ambient and elevated temperatures in relation to the volume fraction of twinning. To evaluate the strain-rate effects, quasi-static compression (10^-3 s^-1) was performed on a standard load frame, whereas a Kolsky (split-Hopkinson pressure) bar, in conjunction with ultra high-speed imaging and 2D digital image correlation (DIC), was used to investigate dynamic compression (up to 10^3 s^-1). In both quasi-static and dynamic loading, an external thermal chamber was used to provide an elevated temperature environment during loading to probe the thermomechanical response. This work will enable a more thorough understanding of the strain-rate and temperature dependence of the volume fraction of twins formed during loading of Ti-15Mo, as well as the strength and ductility balance of these alloys for different applications.

Emily Pittman   Colorado School of Mines
Leslie Lamberson   Colorado School of Mines
Amy Clarke   Colorado School of Mines