Microcavity-induced stress corrosion cracking: The role of boundary sliding and interfacial products in a Zn-Li alloy

• Zn and Zn-0.8Li alloy exhibit enhanced strain softening at 37°C compared to RT. • Li increases the SCC susceptibility of Zn alloy in NaCl solution. • Boundary sliding and micro-galvanic corrosion induce microcavities in Zn-0.8Li alloy. • Precipitation of interfacial corrosion products restricts plastic deformation. Biodegradable zinc-based alloys are typically subjected to coupled mechanical stress and physiological corrosion in vivo. However, the resulting stress-corrosion synergy and failure mechanisms remain elusive. This study systematically investigated the stress corrosion cracking (SCC) susceptibility of a promising Zn-0.8Li (wt.%) alloy using slow strain rate tensile testing in 0.9% NaCl solution, with pure Zn as the control. Results demonstrate that both pure Zn and Zn-0.8Li alloy exhibited enhanced strain softening at physiological temperature (37°C) compared to room temperature. Alloying with Li increases the SCC susceptibility of Zn, primarily reducing elongation by ∼20% while maintaining > 98% of both yield and ultimate tensile strength. Microstructural analyses reveal that boundary sliding and micro-galvanic corrosion induce microcavity formation in the Zn-0.8Li alloy, thereby facilitating corrosive medium ingress into the matrix. Subsequent precipitation of interfacial corrosion products (mainly Zn(OH) 2 /ZnO and LiOH/Li 2 O as identified by X-ray diffraction and X-ray photoelectron spectroscopy) restricts further plastic deformation, accelerating premature fracture. This study provides a theoretical framework for understanding SCC mechanisms in high-ductility alloys where grain boundary-mediated deformation acts as the predominant deformation mode.