Electrochemical and mechanical performance of biodegradable ZX30 alloy using multi-channel spiral twist extrusion (MCSTE) for biomedical implants

Abstract

Multi-channel spiral twist extrusion (MCSTE) is an emerging severe plastic deformation (SPD) technique that offers tunable processing parameters and potential for scalable deformation of bulk billets. This study investigates the effects of MCSTE processing parameters, including twist angles of 30° and 40°, processing routes A and C, and up to eight passes on the microstructure, mechanical performance, and electrochemical behavior of ZX30 magnesium alloy for biodegradable implant applications. Microstructural characterization via scanning electron microscopy, EBSD, and energy-dispersive X-ray spectroscopy revealed that combined route A with incremental passes promote finer grain sizes and more randomized textures compared to route C. Route C developed more pronounced texture and relatively courser grains. After eight passes via Route A at 30°, an 82 % reduction in grain size and a 54 % increase in ultimate tensile strength were achieved relative to the as-annealed condition. Corrosion resistance in simulated body fluid also improved significantly, with Route C at 30° showing a 221 % increase in polarization resistance. While microstructural heterogeneity, particularly an edge-to-center gradient, persists even after multiple passes, these results demonstrate that MCSTE can effectively enhance key functional properties of biodegradable ZX30-Mg alloys. The process remains under development, but its parameter flexibility and compatibility with bulk forms make it a possible candidate for further optimization toward biomedical applications.