| About this Abstract |
| Meeting |
2025 TMS Annual Meeting & Exhibition
|
| Symposium
|
Phase Transformations and Microstructural Evolution
|
| Presentation Title |
Effects of Chemistry, Precipitation, and Microcleanliness on The Structural Degradation of NiTiHf High-Temperature Shape Memory Alloys |
| Author(s) |
Roberto Orrostieta, Ibrahim Karaman |
| On-Site Speaker (Planned) |
Roberto Orrostieta |
| Abstract Scope |
NiTiHf High-temperature shape memory alloys (HTSMAs) are thermal and/or stress-activated solid-state actuators via martensitic transformation at temperatures above 100°C. Their lightweight and compactness are of great interest for applications in the aerospace, defense, and energy industries. Nonetheless, the acute sensitivity to Ni-content in Ni-rich NiTiHf can lead to large transformation temperature changes (~100°C) with Ni-content variations smaller than 1 at. %. Unfortunately, the effect of such chemistry changes on structural degradation is less understood. This work seeks to elucidate not only the effects of Ni-content, but also the effects of precipitation and microcleanliness on structural degradation by performing fracture toughness and fatigue crack growth experiments in a Ni-rich, Ni-medium, and Ni -lean NiTiHf HTSMAs, all three with nominally Ni50.3TiHf20 (at. %) composition and Ni-content variations of < 1 at.%, in precipitate-free and nanoprecipitation hardened microstructures across martensitic transformation. Microstructural features were proven to override chemistry effects on failure responses. |
| Proceedings Inclusion? |
Planned: |
| Keywords |
Phase Transformations, High-Temperature Materials, Mechanical Properties |