|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Bulk Metallic Glasses XIV
||In-situ Synchrotron High-energy X-ray Diffraction Study of an Amorphous/Nanocrystalline NiTi Alloy during Recrystallization Process
||Cun Yu, Bachir Aoun, Lishan Cui, Yinong Liu, Yang Ren
|On-Site Speaker (Planned)
NiTi shape memory alloys form amorphous/nanocrystalline mixtures after severe deformation or during film fabrication. To utilize the shape-memory-effect and superelasticity, the mixtures need to be recrystallized via thermal treatment. We used in-situ synchrotron high-energy diffraction coupled with pair-distribution-function (PDF) analysis to study atomistic structural evolution of a severely cold drawn NiTi wire during thermal annealing. It was found that the wire consisted of mainly amorphous phase (~92%) with some nanocrystalline domains. PDF analysis revealed that the amorphous regions underwent structural relaxation via atomic rearrangement above 100 C, which is correlated with an exothermal anomaly in the differential scanning calorimetry curve, before recrystallization. The nanocrystalline domains exhibit a strong cold work induced lattice strain anisotropy, which is gradually released upon heating above 200 C. With further heating nano-grains started to grow accompanied by reducing microstrain. The results will also help us understand the microstructures of nanocomposites with bulk metallic glass matrix.
||Planned: Supplemental Proceedings volume