About this Abstract |
Meeting |
2020 TMS Annual Meeting & Exhibition
|
Symposium
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Deformation and Transitions at Grain Boundaries VII
|
Presentation Title |
Fatigue-crack Healing in Pure Nanocrystalline Pt Enabled by Boundary Evolution |
Author(s) |
Christopher M Barr, Ta Duong, Daniel Bufford, Nathan Heckman, Michael J. Demkowicz, Khalid Hattar, Brad L. Boyce |
On-Site Speaker (Planned) |
Brad L. Boyce |
Abstract Scope |
In most structural materials, fatigue cracks are assumed to only advance or arrest, with no possibility of retreat. However, by observing high-cycle fatigue of nanocrystalline Pt with in-situ transmission electron microscopy, we observed unexpected nanoscale crack healing. Under tension-tension fatigue loading, a fatigue crack was observed to propagate through a field of nanocrystalline grains, deflecting along expected cleavage planes and arresting in proximity to a triple junction. Over the course of 100K cycles, the crack tip subsequently healed about one grain diameter and eventually propagated in a different direction. Such behavior may be explained by the grain boundary evolution. Molecular dynamics analysis of the crystallographic configuration suggests that a near-Σ3 boundary migrated ahead of the crack tip, resulting in contact between crack flanks and cold welding. There are several implications for the observed crack healing behavior, including a possible explanation for enhanced crack growth resistance under mixed mode loading conditions. |
Proceedings Inclusion? |
Planned: Supplemental Proceedings volume |