|About this Abstract
||2022 TMS Annual Meeting & Exhibition
||Phase Transformations and Microstructural Evolution
||The Effect of Precipitate Size on the Thermo-mechanical Properties of Ni-Ti-Hf-Al Shape Memory Alloys
||Ching-Chien Chen, Shivam Tripathi, Alexandra Loaiza, David F. Bahr, Alejandro Strachan, Michael S. Titus
|On-Site Speaker (Planned)
The presence of coherent precipitates can significantly tune the transformation behavior in martensitic materials and can result in unprecedented thermomechanical properties. The addition of Al as an alloying element to high-temperature Ni-Ti-Hf-based shape memory alloys has been shown to result in the formation of coherent Ni<sub>2</sub>TiAl Heusler precipitates, which could lead to unique properties. In this study, we systematically investigate the role of Ni<sub>2</sub>TiAl Heusler precipitates on the thermo-mechanical properties of Ni-Ti-Hf-Al based shape memory alloys. A combination of calorimetry, nanoindentation, and high-resolution transmission electron microscopy was used to characterize the shape memory alloy behavior. We find that the precipitates initially exhibit an austenite-stabilizing behavior but coarsening of the precipitates and chemical partitioning subsequently stabilizes martensite. Comparisons of strength, modulus, thermal hysteresis, and remnant strain will be made between experiments and molecular dynamics simulations.
||Other, Phase Transformations, Characterization