A Review of Friction Stir Processing of Al-Bronze Reinforced with Rare Earth Metal Powders

The present work focuses on the recent advancements in friction stir processing (FSP) of aluminum bronze reinforced with rare earth metal powders for marine applications. Aluminum bronze alloys are extensively used in marine components due to their exceptional corrosion resistance, strength, and antifouling behavior. Conventional casting and heat-treatment methods often result in coarse-grained microstructures and reduced performance under severe seawater conditions. FSP, a solid-state surface modification technique, has emerged as a promising approach to overcome these limitations by refining grain structures, enhancing hardness, and improving corrosion behavior. The paper scientifically reviews the effect of FSP parameters, tool geometry, and rare earth reinforcement materials such as CeO2, Y2O3, and La2O3 on microstructural evolution, mechanical strength, and corrosive behavior of aluminum bronze composites. Among numerous practices, submerged and powder-assisted FSP are found to yield the most promising results, attaining uniform reinforcement dispersion, refined microstructures, and up to 50% enhancement in corrosion resistance compared to non-processed alloys. Optimized tool geometries, explicitly threaded or tapered pins along with concave shoulders further improve material flow and reduce surface defects. The review concludes that FSP provides an energy-efficient and environment friendly viable technique for developing high-performance aluminum bronze composites for propellers, pumps, and other marine components.