Multi-principal element alloys (MPEAs) have attracted widespread attention in recent years as a new class of high-performance materials. In particular, face-centered cubic MPEAs with low stacking fault energy exhibit excellent fracture toughness, making them highly promising for applications in aerospace, energy, and medical fields. The fracture toughness of these alloys is closely related to the abundant deformation twins within their microstructure. However, the microscopic mechanism by which deformation twins affect crack propagation remains unclear, especially the role of coherent twin boundaries (CTBs) in crack propagation.
Methods
Highlights
During crack propagation, the interaction between the crack and CTBs can induce twin boundary sliding and the nucleation of secondary nanotwins, leading to a zig-zag crack propagation path.
Secondary nanotwins effectively blunt the crack tip, thereby improving the fracture toughness of the material.
Quantitative analysis indicates that this crack-twin boundary interaction mechanism can nearly double the crack propagation resistance of the material.
Fig. 2. Microscopic zig-zag crack propagation in the vicinity of a pre-existing coherent TB.
This study reveals the critical role of deformation twins and CTBs in the fracture toughness of MPEAs, providing new insights into the understanding of the excellent mechanical properties of these alloys. The theoretical framework of twin boundary-regulated crack propagation is improved, which offers theoretical guidance for the design of high-performance alloys.
Prof. Hua-jian Gao is a leading expert in the field of mechanics, materials science, and engineering science. He currently serves as the Dean of the School of Mechanics and Engineering at Tsinghua University. He is also a prestigious academician of seven academies: a foreign academician of the Chinese Academy of Sciences, an academician of the National Academy of Sciences (USA), an academician of the National Academy of Engineering (USA), an academician of the American Academy of Arts and Sciences, an academician of the German National Academy of Sciences, a foreign academician of the Academia Europaea, and a fellow of the Royal Society.
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Editor: Dr. Jun-Jing He
