Composition-dependent fracture energy in metallic glasses

H Li and JC Zhang and PS Branicio and ZD Sha, PHYSICAL REVIEW MATERIALS, 7, 035602 (2023).

DOI: 10.1103/PhysRevMaterials.7.035602

The interplay between metallic glasses (MGs) mechanical properties, fracture energy (G), and glass-forming ability (GFA) and their dependence on alloy composition remain poorly understood. Here, we perform molecular dynamics simulations to investigate the intrinsic composition dependence of G in CuxZr100-xMGs (x = 20, 30, 40, 50, 64). The results indicate that the value of G increases with Cu content. In addition, it is revealed that MGs with higher G values display higher Poisson's ratio (v) and GFA, suggesting a close correlation between fracture toughness, mechanical properties, and GFA. This correlation between G, v, and GFA can be understood based on the fragility (m) of supercooled liquids, which is directly related to the structural heterogeneity in MGs. Larger m values are related to dynamic slowdown and supercooled liquid stabilization, which enhance GFA and the formation of pronounced structural heterogeneity, comprised of loosely packed regions that favor beta relaxation and the activation of shear transformation zones. Those concurrently promote the expansion of the plastic zone at the crack tip, enhancing the observed value of G. These simulation results shed light on the intrinsic relationship between fracture toughness, mechanical properties, and alloy composition in MGs.

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