Intergranular crack arrest in FCC metals with distinct stacking fault energy

Abstract

The influence of stacking fault energy (SFE) on the microstructure and mechanical properties of materials is a well-established topic, however, its universality in metal crystals remains unchallenged. In this work, molecular dynamics simulations are employed to explore intergranular crack propagation in metals with distinct SFEs, i.e., Al, Ni, Cu, and Ag, as bicrystals, tricrystals, and polycrystals. It is found that the crack arrest capability does not follow the indication from SFEs in both bicrystal and tricrystal cases. The key mechanism behind the enhanced crack arrest capability arises from dislocation hardening in bicrystals, leading to an increase in the J-integral. Besides dislocation hardening, the dislocation motion also makes a great contribution to improving the crack arrest capability in tricrystals, also increasing the J-integral. In contrast, polycrystals follow the guidance of SFE as expected, and the governing mechanism lies in the density of planar defects, as lower SFE promotes ductility. Our findings challenge the broadly accepted notion that reducing SFE universally enhances crack arrest capability. This study provides valuable insights into the mechanisms of intergranular crack propagation and arrest in metals with distinct SFEs, offering guidance for the design of advanced materials with superior mechanical performance.