About this Abstract |
Meeting |
2021 TMS Annual Meeting & Exhibition
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Symposium
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Materials for High Temperature Applications: Next Generation Superalloys and Beyond
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Presentation Title |
Segregation-assisted Climb of Frank Partial Dislocations: A Novel Planar Fault Formation Mechanism in L12-hardened Superalloys |
Author(s) |
Malte Lenz, Erdmann Spiecker, Mingjian Wu |
On-Site Speaker (Planned) |
Malte Lenz |
Abstract Scope |
In this work, we provide the first experimental evidence for the formation of superlattice intrinsic stacking faults (SISF) by climb of Frank partial (FP) dislocations, a mechanism postulated by Kear et al. in the 1970s. The observation was made in a multinary Co-based superalloy after [001] tensile creep (850 °C/400 MPa/4.6%). A high-resolution analysis revealed a formation mechanism where a Lomer-type channel dislocation becomes incorporated into the precipitate phase and then dissociates into a pinned Shockley partial and a climbing Frank partial, according to: a/2[1-10]→a/3[1-1-1]+a/6[1-12]. The FP is driven forward by an osmotic force arising from a vacancy supersaturation and moves counteracting climb force created by external loading. This mechanism is sustainable since FPs act as internal vacancy sinks absorbing vacancies emitted during climb of matrix dislocations. The climb motion of FPs is assisted by segregation of solutes to the dislocation core and SISF, lowering the fault energy. |
Proceedings Inclusion? |
Planned: |