Grain refinement and corrosion behavior of biodegradable Mg: A review on mechanisms and controversies

Modifying grain boundaries (GBs) and interfacial structures is a classic and critical strategy for altering the properties of metallic materials. Controlling grain boundaries can significantly improve the mechanical properties, corrosion resistance, and biocompatibility of biodegradable magnesium (Mg) alloys. However, the complex microstructural changes that occur during grain refinement have led to conflicting research findings regarding how GBs influence the corrosion resistance of Mg alloys. Guided by the concept of material plainification and drawing on established microstructural design principles for industrial Mg alloys, this study systematically analyzes the positive and negative roles of grain boundaries, while separately evaluating the effects of accompanying factors, including texture, twins, dislocations, and secondary phases. By integrating these factors, this research proposes a dialectical framework that elucidates how various microstructural factors influence the degradation of Mg alloys during grain refinement. This study not only provides a theoretical basis for resolving the controversy regarding grain refinement and corrosion in biodegradable Mg alloys but also offers a novel approach and practical guidance for designing high-performance, simplified-composition medical Mg alloys based on industrial experience.