材料科学
断裂韧性
层错能
韧性
延展性(地球科学)
成核
复合材料
位错
冶金
马氏体
合金
微观结构
蠕动
热力学
物理
作者
Dong Liu,Qin Yu,Saurabh Kabra,Ming Jiang,Paul Forna-Kreutzer,Ruopeng Zhang,Madelyn I. Payne,Flynn Walsh,Bernd Gludovatz,Mark Asta,Andrew M. Minor,E.P. George,Robert O. Ritchie
出处
期刊:Science
[American Association for the Advancement of Science (AAAS)]
日期:2022-12-01
卷期号:378 (6623): 978-983
被引量:192
标识
DOI:10.1126/science.abp8070
摘要
CrCoNi-based medium- and high-entropy alloys display outstanding damage tolerance, especially at cryogenic temperatures. In this study, we examined the fracture toughness values of the equiatomic CrCoNi and CrMnFeCoNi alloys at 20 kelvin (K). We found exceptionally high crack-initiation fracture toughnesses of 262 and 459 megapascal-meters½ (MPa·m½) for CrMnFeCoNi and CrCoNi, respectively; CrCoNi displayed a crack-growth toughness exceeding 540 MPa·m½ after 2.25 millimeters of stable cracking. Crack-tip deformation structures at 20 K are quite distinct from those at higher temperatures. They involve nucleation and restricted growth of stacking faults, fine nanotwins, and transformed epsilon martensite, with coherent interfaces that can promote both arrest and transmission of dislocations to generate strength and ductility. We believe that these alloys develop fracture resistance through a progressive synergy of deformation mechanisms, dislocation glide, stacking-fault formation, nanotwinning, and phase transformation, which act in concert to prolong strain hardening that simultaneously elevates strength and ductility, leading to exceptional toughness.
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