Kink bands promote exceptional fracture resistance in a NbTaTiHf refractory medium-entropy alloy
成果类型：
Article
署名作者：
Cook, David H.; Kumar, Punit; Payne, Madelyn I.; Belcher, Calvin H.; Borges, Pedro; Wang, Wenqing; Walsh, Flynn; Li, Zehao; Devaraj, Arun; Zhang, Mingwei; Asta, Mark; Minor, Andrew M.; Lavernia, Enrique J.; Apelian, Diran; Ritchie, Robert O.
署名单位：
University of California System; University of California Berkeley; United States Department of Energy (DOE); Lawrence Berkeley National Laboratory; University of California System; University of California Irvine; United States Department of Energy (DOE); Pacific Northwest National Laboratory; United States Department of Energy (DOE); Lawrence Berkeley National Laboratory
刊物名称：
SCIENCE
ISSN/ISSBN：
0036-11215
DOI：
10.1126/science.adn2428
发表日期：
2024-04-12
页码：
178-184
关键词：
high-temperature strength
niobium single-crystals
toughness
deformation
microstructure
room
initiation
stress
strain
energy
摘要：
Single-phase body-centered cubic (bcc) refractory medium- or high-entropy alloys can retain compressive strength at elevated temperatures but suffer from extremely low tensile ductility and fracture toughness. We examined the strength and fracture toughness of a bcc refractory alloy, NbTaTiHf, from 77 to 1473 kelvin. This alloy's behavior differed from that of comparable systems by having fracture toughness over 253 MPam(1/2), which we attribute to a dynamic competition between screw and edge dislocations in controlling the plasticity at a crack tip. Whereas the glide and intersection of screw and mixed dislocations promotes strain hardening controlling uniform deformation, the coordinated slip of <111> edge dislocations with {110} and {112} glide planes prolongs nonuniform strain through formation of kink bands. These bands suppress strain hardening by reorienting microscale bands of the crystal along directions of higher resolved shear stress and continually nucleate to accommodate localized strain and distribute damage away from a crack tip.