The poor corrosion resistance and high susceptibility to stress corrosion cracking (SCC) of magnesium alloys limit their potential in biodegradable implant applications. This study systematically investigates the corrosion behavior and SCC resistance of ZK60 magnesium alloy processed by multi-directional compression (MDC). A combination of electrochemical measurements, slow strain rate tensile (SSRT) testing, and advanced microstructural characterization was employed to evaluate the material’s performance in phosphate buffer solution (PBS). The results demonstrate that MDC processing significantly refines the grain structure from 19.69 µm (T4) to 7.89 µm (12MDC), simultaneously increasing dislocation density and fragmenting second-phase particles. These microstructural modifications shift the corrosion mechanism from localized pitting to uniform corrosion, reducing the electrochemical corrosion rate by 42.8% and the hydrogen evolution corrosion rate by 88.6% in the 12MDC sample. Furthermore, the ε- and UTS-related SCC susceptibility indices are reduced by 14.7% (12MDC) and 17.5% (6MDC), respectively, compared with the T4 sample, which is attributed to the dense twin/grain boundary networks that deflect cracks and dissipate fracture energy. The synergistic effects of grain refinement, dislocation strengthening, and Orowan mechanism collectively enhance both mechanical properties and corrosion resistance. This work confirms that MDC processing effectively improves the functional reliability of ZK60 alloy for biomedical applications through microstructural optimization.

Strong anisotropic corrosion and mechanical properties caused by specimen orientations greatly limit the applications of wrought magnesium alloys. To investigate the influences of specimen orientation, the corrosion tests and (corrosion) fatigue crack growth tests were conducted. The rolled and transverse surfaces of the materials show distinct corrosion rate differences in the stable corrosion stage, but the truth is the opposite for the initial stage of corrosion. In air, specimen orientations have a significant influence on the plastic deformation mechanisms near the crack tip, which results in different fatigue fracture surfaces and cracking paths. Compared with R-T specimens, N-T specimens show a slower fatigue crack growth (FCG) rate in air, which can be attributed to crack closure effects and deformation twinning near the crack tip. The corrosion environment will not significantly change the main plastic deformation mechanisms for the same type of specimen. However, the FCG rate in phosphate buffer saline (PBS) is one order of magnitude higher than that in air, which is caused by the combined effects of hydrogen-induced cracking and anodic dissolution. Owing to the similar corrosion rates at crack tips, the specimens with different orientations display close FCG rates in PBS.