A review of friction stir-based techniques for magnesium alloys: Welding, processing, recycling, and additive manufacturing

Magnesium (Mg) alloys are increasingly vital in aerospace, automotive, electronics, and biomedical industries due to their high strength-to-weight ratio and recyclability. Conventional fusion-based methods often face limitations in joining and processing Mg alloys, which has driven the development of friction stir-based techniques (FSTs) as promising solid-state alternatives. This review provides a comprehensive assessment of FSTs applied to magnesium alloys, covering friction stir welding for Mg–Mg and Mg–Al joints with attention to process parameters, and tool design; friction stir processing for microstructural refinement and surface composite fabrication; friction stir extrusion as a sustainable route for recycling machining chips into wires, and tubes; and friction stir additive manufacturing as a rapidly advancing approach for solid-state, layer-by-layer fabrication. The review highlights the current state, challenges, and opportunities of these techniques, emphasizing their potential to enhance performance, sustainability, and industrial applicability of magnesium alloys.