About this Abstract |
Meeting |
2024 TMS Annual Meeting & Exhibition
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Symposium
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Fatigue in Materials: Fundamentals, Multiscale Characterizations and Computational Modeling
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Presentation Title |
In-situ Characterization of Dislocation Density Evolution in Nickel-titanium Shape Memory Alloys During Load-biased Thermal Cycling Using High-energy Diffraction Microscopy |
Author(s) |
Wenxi Li, Sangwon Lee, Tianchi Zhang, Yuefeng Jin, Darren Pagan, Lee Casalena, Michael Mills, Ashley Bucsek |
On-Site Speaker (Planned) |
Wenxi Li |
Abstract Scope |
Functional fatigue is a major barrier to the cycle lifetime demands of shape memory alloy technologies. Functional fatigue is caused by permanent changes to the microstructure during the martensitic phase transformation. In this work, far-field and near-field high-energy diffraction microscopy (ff/nf-HEDM) are used to characterize the intragranular accumulation of geometrically necessary dislocation (GND) density in situ across a bulk nickel-titanium shape memory alloy during load-biased thermal cycling. A custom nf-HEDM data analysis is used to reconstruct spatially resolved intragranular misorientation maps, which are then converted to spatially resolved GND density maps. In this way, the 3D evolution of GND density inside individual grains can be tracked during loading. We find that GND density increases faster near grain boundaries and in grains near the sample surface, with large volumes, and with many neighbors. Neither the Schmid factor nor the maximum transformation work shows a strong correlation with GND density evolution. |
Proceedings Inclusion? |
Planned: |
Keywords |
Characterization, Mechanical Properties, |