About this Abstract |
| Meeting |
MS&T22: Materials Science & Technology
|
| Symposium
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Integration between Modeling and Experiments for Crystalline Metals: From Atomistic to Macroscopic Scales IV
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| Presentation Title |
Unexpected Deformation-Induced Martensitic Transformations in Ni-Cr Alloy 625 |
| Author(s) |
Janelle P. Wharry, Caleb D Clement, Chao Yang |
| On-Site Speaker (Planned) |
Janelle P. Wharry |
| Abstract Scope |
The objective of this talk is to demonstrate unexpected deformation-induced martensitic transformations in Ni-Cr superalloys. In fcc crystals, deformation-induced bcc and/or hcp martensites form through diffusionless, solid-state phase transformations. Martensitic transformations are not believed to be active in high-stacking fault energy (SFE) materials such as Ni-Cr superalloys. Here, we present novel nanoscale martensitic transformations under high strain rate deformation in Alloy 625 (nominally Ni-20Cr-8Mo). Nanoindentations are dissected using focused ion beam milling to extract transmission electron microscopy (TEM) lamellae. High resolution scanning TEM (HR-STEM) reveals nanoscale deformation twinning and martensites, often only a few atomic layers thick. Inverse fast Fourier transformations (FFT) suggest that both hcp and bcc martensites form. Molecular dynamics simulations of Ni-20Cr concur that martensitic transformations occur following stacking fault formation. These results have significant implications for the mechanical behavior of Ni-Cr superalloys, and more fundamentally, challenge our understanding of SFE as a criterion for martensitic transformations. |