NSUF 22-4415: Irradiation Effects on Unexpected Deformation-Induced Martensitic Phase Transformation in Ni-alloys
The objective of this project is to understand how irradiation-induced defects affect the surprising, previously unreported deformation-induced martensitic transformations recently observed in a Ni-based superalloy. The mechanical behavior of Ni-based alloys has always been attributed to conventional fcc deformation mechanisms: dislocation plasticity, localized dislocation channeling upon irradiation, and dislocation twinning in the presence of precipitates or at cryogenic temperatures. But our recent NSUF-supported work on unirradiated and 1 dpa neutron irradiated Ni-base Alloy 625 has revealed surprising room temperature deformation-induced fcc-to-hcp and fcc-to-bcc martensitic transformations previously unreported in Ni superalloys. The martensites nucleated in the irradiated material differ from those in the as-received material. This is consistent with previous research on steels, which show that the critical transformation stresses for epsilon-hcp and alpha’-bcc martensite variants are sensitive to irradiation-induced cavity (i.e., bubbles and void) configurations. We therefore hypothesize that irradiation-induced cavities similarly enhance the tendency for deformation-induced martensitic transformability of Ni alloys by activating epsilon and/or alpha’ transformations. To resolve our hypothesis, we propose an approach to conduct proton, helium, and proton+helium dual-beam irradiations on Alloy 625, with subsequent grain orientation-dependent nanoindentation and transmission electron microscopic (TEM) deformation microstructure characterization. Here, the proposed single- and dual-beam irradiations are specifically designed to enable us to decouple the role of cavities from dislocation loops on deformation-induced phase transformations. Examining different grain orientations will also enable us to link the phase transformation to critical resolved shear stress. Work will be conducted at the Michigan Ion Beam Laboratory (MIBL) and the Center for Advanced Energy Studies (CAES).
Additional Info
| Field | Value |
|---|---|
| Abstract | The objective of this project is to understand how irradiation-induced defects affect the surprising, previously unreported deformation-induced martensitic transformations recently observed in a Ni-based superalloy. The mechanical behavior of Ni-based alloys has always been attributed to conventional fcc deformation mechanisms: dislocation plasticity, localized dislocation channeling upon irradiation, and dislocation twinning in the presence of precipitates or at cryogenic temperatures. But our recent NSUF-supported work on unirradiated and 1 dpa neutron irradiated Ni-base Alloy 625 has revealed surprising room temperature deformation-induced fcc-to-hcp and fcc-to-bcc martensitic transformations previously unreported in Ni superalloys. The martensites nucleated in the irradiated material differ from those in the as-received material. This is consistent with previous research on steels, which show that the critical transformation stresses for epsilon-hcp and alpha’-bcc martensite variants are sensitive to irradiation-induced cavity (i.e., bubbles and void) configurations. We therefore hypothesize that irradiation-induced cavities similarly enhance the tendency for deformation-induced martensitic transformability of Ni alloys by activating epsilon and/or alpha’ transformations. To resolve our hypothesis, we propose an approach to conduct proton, helium, and proton+helium dual-beam irradiations on Alloy 625, with subsequent grain orientation-dependent nanoindentation and transmission electron microscopic (TEM) deformation microstructure characterization. Here, the proposed single- and dual-beam irradiations are specifically designed to enable us to decouple the role of cavities from dislocation loops on deformation-induced phase transformations. Examining different grain orientations will also enable us to link the phase transformation to critical resolved shear stress. Work will be conducted at the Michigan Ion Beam Laboratory (MIBL) and the Center for Advanced Energy Studies (CAES). |
| Award Announced Date | 2022-06-14T07:23:12.02 |
| Awarded Institution | Idaho National Laboratory |
| Facility | Advanced Test Reactor |
| Facility Tech Lead | Alina Zackrone, Kevin Field, Yaqiao Wu |
| Irradiation Facility | Michigan Ion Beam Laboratory |
| PI | Caleb Clement |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 4415 |