| About this Abstract |
| Meeting |
2025 TMS Annual Meeting & Exhibition
|
| Symposium
|
Phase Transformations and Microstructural Evolution
|
| Presentation Title |
On the effects of micro-scale concentration gradients on martensitic transformations in NiTi shape memory alloys |
| Author(s) |
Jan Frenzel, Oluwaseyi Oluwabi, Gunther Eggeler |
| On-Site Speaker (Planned) |
Jan Frenzel |
| Abstract Scope |
The martensitic transformation in NiTi shape memory alloys (SMAs) strongly depends on composition and microstructure. It not clear how chemical gradients affect transformation behavior. In the present work, binary NiTi diffusion couples were subjected to in-situ cooling in a scanning electron microscope. The experiments allowed to trace the propagation of transformation fronts into regions with higher Ni-concentrations / lower transformation temperatures. Our data suggest that a correlation exists between the steepness of the gradient and the driving force which is needed to push transformation fronts forward towards regions where the low temperature phase is unstable. We also document that the martensite, which grows in opposite direction to the gradient, has a significantly finer structure as when it forms in a homogeneous material. These findings suggest that compositional gradients impose “chemical constraints” which limit the available space for twinning accommodation and thus result in higher barriers for the transformation. |
| Proceedings Inclusion? |
Planned: |
| Keywords |
Phase Transformations, Characterization, |