A review on in-situ aluminum metal matrix composites manufactured via friction stir processing: meeting on-ground industrial applications

Purpose In-situ aluminum metal matrix composites (AMMC) have taken over the use of ex-situ AMMC due to the generation of finer and thermodynamically stable intermetallic compounds. However, conventional processing routes pose inevitable defects like porosity and agglomeration of particles. This paper aims to study current state of progress in in-situ AMMC fabricated by Friction Stir Processing. Design/methodology/approach Friction stir processing (FSP) has successfully evolved to be a favorable in-situ composite manufacturing technique. The dynamics of the process account for a higher plastic strain of 35 and a strain rate of 75 per second. These processing conditions are responsible for grain evolution from rolled grain → dislocation walls and dislocation tangles → subgrains → dislocation multiplication → new grains. Working of matrix and reinforcement under ultra-high strain rate and shorter exposure time to high temperatures produce ultra-fine grains. Do the grain evolution modes include subgrain boundaries → subgrain boundaries and high angle grain boundaries → high angle grain boundaries. Findings Further, the increased strain and strain rate can shave and disrupt the oxide layer on the surface of particles and enhance wettability between the constituents. The frictional heat generated by tool and workpiece interaction is sufficient enough to raise the temperature to facilitate the exothermic reaction between the constituents. The heat released during the exothermic reaction can even raise the temperature and accelerate the reaction kinetics. In addition, heat release may cause local melting of the matrix material which helps to form strong interfacial bonds. Originality/value This article critically reviews the state of the art in the fabrication of in-situ AMMC through FSP. Further, FSP as a primary process and post-processing technique in the synthesis of in-situ AMMC are also dealt with.