Appearance of reinforcement, interfacial product, heterogeneous nucleant and grain refiner of MgAl2O4 in aluminium metal matrix composites

The role of MgAl2O4 particles in Al matrix composites has been very crucial. They have evolved from acting as a product at the matrix-reinforcement interface of some ex-situ aluminium matrix composites (AMCs) to a separate reinforcement in the in-situ AMCs. In recent times, they have also been used as a nucleating agent in the form of Al–MgAl2O4 master alloy to propagate the grain refinement process in commercial Al alloys for microstructural changes. In this context, this work reviews the recent developments of MgAl2O4 formation in Al–Mg–Al2O3 and Al–Mg–SiC composites. It summarizes the influence of MgAl2O4 on surface morphology and mechanical characteristics during their formation at the matrix-reinforcement interface. Furthermore, a thorough study on the impact of MgAl2O4 as a reinforcement formed via the in-situ reactive synthesis in AMCs using Al–Mg matrix and different oxide sources namely SiO2, TiO2, and H3BO3 has been carried out. Various results on the grain refinement process obtained using MgAl2O4 as a heterogeneous nucleating agent in Al alloys have been also deliberated in this review.