| About this Abstract |
| Meeting |
2023 TMS Annual Meeting & Exhibition
|
| Symposium
|
Advances in Multi-Principal Element Alloys II
|
| Presentation Title |
Exceptional Fracture Toughness of CrCoNi-based Alloys Close to Liquid Helium Temperatures |
| Author(s) |
Robert O. Ritchie, Dong Liu, Qin Yu, Saurabh Kabra, Madelyn Payne, Ruopeng Zhang, Flynn Walsh, Bernd Gludovatz, Mark Asta, Andrew M. Minor, Easo P. George, Punit Kumar |
| On-Site Speaker (Planned) |
Punit Kumar |
| Abstract Scope |
CrCoNi-based medium/high-entropy alloys show outstanding strength, ductility and toughness, especially at cryogenic temperatures. Here we examine their fracture toughness at 20 K. At a flow stress ~1.5 GPa, exceptionally high crack-initiation KJIc toughnesses were found, respectively 235 and 415 MPa√m for CrMnFeCoNi and CrCoNi, with the CrCoNi alloy displaying a crack-growth toughness Kss exceeding 540 MPa√m, which we believe is the highest toughness ever reported. Characterization of the crack-tip regions reveal deformation structures at 20 K that involve heterogeneous nucleation, but restricted growth, of stacking faults and fine nano-twins, together with limited transformation to epsilon-martensite. The extreme fracture resistance results from a progression of deformation mechanisms - dislocation glide, stacking-fault formation, nano-twinning and eventually in situ phase transformation - that generates prolonged strain hardening to elevate strength and ductility (by delaying plastic instability), resulting in exceptional toughness. |
| Proceedings Inclusion? |
Planned: |
| Keywords |
High-Entropy Alloys, Mechanical Properties, Characterization |