Abstract
This study aimed to analyze how the addition of titanium (Ti) to TiAlTa alloys affects their mechanical properties (Young's modulus and hardness) and oxidation behavior. Alloys with three different Ti additions and equi-atomic Al and Ta were fabricated with nominal compositions of 33Ti-33Al-33Ta at%, 50Ti-25Al-25Ta at%, and 70Ti-15Al-15Ta at%. Phase identification of as-processed and compositionally homogenized alloys was conducted by coupling various electron microscopy, diffraction, and chemical analysis techniques. Composition and structures were modeled using CALPHAD-based phase predictions and compared with experimental results. Each of the alloys exhibited a unique set of microstructures with distinctly different ordered precipitates, dependent on cooling rate and chemical composition. Subsequently, nanoindentation tests were performed at temperatures of 25 °C, 250 °C, 500 °C, and 750 °C. Oxidation studies were conducted under static air at 750°C for up to 200 h. 33Ti-33Al-33Ta at% and 70Ti-15Al-15Ta at% alloys showed higher hardness and modulus than 50Ti-25Al-25Ta at% at room temperature. The 50Ti-25Al-25Ta at% alloy exhibited higher hardness and modulus values but lower oxidation resistance at 750°C when compared with the other specimens. The X-ray photoelectron spectroscopy experiments were conducted to further analyze the oxides present in the samples. Despite each sample displaying combinations of mixed oxide layers, TiO2 was the preferred oxide forming in the 50Ti-25Al-25Ta composition, while the other samples preferred to form Al2O3. The findings from this systematic exploration of phase evolution in the TiAlTa alloy space provide insights for optimized material chemistries, processing, and properties.
| Original language | English |
|---|---|
| Article number | 172883 |
| Journal | Journal of Alloys and Compounds |
| Volume | 973 |
| DOIs | |
| State | Published - Feb 5 2024 |
Funding
This work was sponsored by the Oak Ridge National Laboratory - the Director's Research and Development (LDRD) Fund under Strategic Hire Initiative. Microscopy was performed as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility. STEM-EDS analysis research was performed using instrumentation (FEI Talos F200X S/TEM) provided by the Department of Energy, Office of Nuclear Energy, Fuel Cycle R&D Program and the Nuclear Science User Facilities. Authors J.T. and S.N. would like to acknowledge Tracie Lowe for preliminary SEM analyses of oxidized specimens, Ray Unocic and Kinga Unocic for the TEM analysis, Ercan Cakmak for XRD support, and Jefferey Baxter for site-specific sample preparation using the focused ion beam tool. Authors Y.W. and P.N. would like to acknowledge the Utah Nanofab technicians for helping and training during the experiments. This work was sponsored by the Oak Ridge National Laboratory - the Director’s Research and Development (LDRD) Fund under Strategic Hire Initiative. Microscopy was performed as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility. STEM-EDS analysis research was performed using instrumentation (FEI Talos F200X S/TEM) provided by the Department of Energy, Office of Nuclear Energy, Fuel Cycle R&D Program and the Nuclear Science User Facilities. Authors J.T. and S.N. would like to acknowledge Tracie Lowe for preliminary SEM analyses of oxidized specimens, Ray Unocic and Kinga Unocic for the TEM analysis, Ercan Cakmak for XRD support, and Jefferey Baxter for site-specific sample preparation using the focused ion beam tool. Authors Y.W. and P.N. would like to acknowledge the Utah Nanofab technicians for helping and training during the experiments.
Keywords
- Elevated temperature
- Mechanical properties
- Oxidation kinetics
- TiAlTa