Impact of High Entropy Alloy Reinforcements in Friction Stir Processed Materials - A Detailed Review

Friction Stir Processing (FSP) has emerged as a fundamental solid-state processing method mostly used to improve the mechanical and microstructural characteristics of base metal alloys by means of the reinforcement of High Entropy Alloys (HEAs). The changing approaches and results related to the integration of HEAs in different base metal alloys, including aluminium, copper, magnesium, and steel are carefully examined in this work. Significant improvements in mechanical properties—including yield strength, tensile strength, and wear resistance—annotated across a variety of experimental studies support the synthesis of HEA-reinforced composites using FSP. A clear explanation of the observed improvements depends critically on the Hall-Petch relationship, Zener pinning effect, and Orowan strengthening mechanisms. Furthermore, this study clarifies the complex interactions among processing factors—such as tool shape, rotation speed, traversal speed, and the cooling conditions used during FSP—and the resultant impacts on the grainstructure, including grain refinement, hardness and tribological properties. Evidence shows that FSP promotes homogeneous dispersion of HEA particles inside the matrix, hence improving interfacial bonding and hence composite durability. In addition, the present review covers the possible uses of these HEA-reinforced composites in several sectors, especially in those where exceptional mechanical qualities are essential, including structural, automotive, and aerospace ones. Future directions of investigation are suggested to investigate alternate reinforcing methods, the application of new HEAs, the innovation of surface composites formed through several base metals incorporated with HEAs, and the junction of FSP with advanced production technologies. By means of a thorough synthesis of the literature, this review not only compiles current knowledge about FSP of base metal alloys supporting HEAs but also provides a guiding framework for ongoing innovation in this developing subject.