Research progress in friction stir processing of magnesium alloys and their metal matrix surface composites: Evolution in the 21st century

Abstract

Rising concerns about climate change drive the demand for lightweight components. Magnesium (Mg) alloys are highly valued for their low weight, making them increasingly important in various industries. Researchers focusing on enhancing the characteristics of Mg alloys and developing their Metal Matrix Composites (MMCs) have gained significant attention worldwide over the past decade, driven by the global shift towards lightweight materials. Friction Stir Processing (FSP) has emerged as a promising technique to enhance the properties of Mg alloys and produce Mg-MMCs. Initially, FSP adapted to refine grain size from the micro to the nano level and accelerated the development of MMCs due to its solid-state nature and the synergistic effects of microstructure refinement and reinforcement, improving strength, hardness, ductility, wear resistance, corrosion resistance, and fatigue strength. However, producing defect-free and sound FSPed Mg and Mg-MMCs requires addressing several variables and their interdependencies, which opens up a broad range of practical applications. Despite existing reviews on individual FSP of Mg, its alloys, and MMCs, an attempt has been made to analyze the latest research on these three aspects collectively to enhance the understanding, application, and effectiveness of FSP for Mg and its derivatives. This review article discusses the literature, classifies the importance of Mg alloys, provides a historical background, and explores developments and potential applications of FSPed Mg alloys. It focuses on novel fabrication methods, reinforcement strategies, machine and tool design parameters, material characterization, and integration with other methods for enhanced properties. The influence of process parameters and the emergence of defects are examined, along with specific applications in mono and hybrid composites and their microstructure evolution. The study identifies promising reinforcement materials and highlights research gaps in FSP for Mg alloys and MMCs production. It concludes with significant recommendations for further exploration, reflecting ongoing advancements in this field.