Loading...
Rate effects on the thermo-mechanical compressive response of conventional and metastable β-Ti alloys
Pittman, Emily Rose
Pittman, Emily Rose
Citations
Altmetric:
Advisor
Editor
Date
Date Issued
2024
Date Submitted
Collections
Research Projects
Organizational Units
Journal Issue
Embargo Expires
2026-04-04
Abstract
Titanium and its alloys are known for their high strength-to-weight ratio and are widely used in the defense, aerospace, and automotive industries, where dynamic loading conditions with strain rates from 102 s−1 to over 104 s−1 are common. Alloys exhibiting Twinning Induced Plasticity (TWIP) offer enhanced toughness and ductility under such conditions, but their behavior at high strain rates and elevated temperatures is not well understood. To address this, a specialized thermal Kolsky system capable of testing materials at strain rates around 103 s−1 and temperatures up to 800°C was developed at the Colorado School of Mines. This system utilizes a modified Kolsky bar with an external furnace for heating and a triple actuation system for precise control. It allows for simultaneous ultra high-speed imaging, 2D digital image correlation, and high-speed thermal imaging. Validation experiments on Ti-6Al-4V showed that the system provides reliable data consistent with existing literature.
The strain-rate sensitivity of Ti-15Mo (wt.%) was investigated with regard to initial grain size under both quasi-static and dynamic compressive loading, focusing on its influence on twinning behavior. Results indicated that higher strain-rates lead to increased twinning and reduced work hardening associated with significant adiabatic heating. Smaller-grained samples exhibited a slight reduction in work hardening at low strain rates but showed higher work hardening under dynamic conditions. Further experiments using the developed high-temperature Kolsky system assessed the combined effects of strain-rate and temperature on Ti-15Mo. Twinning remained dominant under high strain-rates, with a reduction in twinning associated with increasing temperature. Under quasi-static conditions, the primary deformation mechanism shifted from twinning to dislocation slip at high temperatures. ω phase precipitation was also observed at high temperatures under quasi-static loading. Yield strength varied with strain-rate and temperature, with work hardening rates higher under quasi-static loading compared to dynamic conditions, influenced by temperature and deformation mechanisms.
Associated Publications
Rights
Copyright of the original work is retained by the author.