As-cast magnesium AM60-based hybrid nanocomposite containing alumina fibres and nanoparticles: Microstructure and tensile behavior

Abstract

Magnesium AM60 based metal matrix hybrid nanocomposite (MHNC) reinforced with alumina (Al2O3) fibre and nano-sized Al2O3 particles was successfully fabricated by a perform-squeeze casting technique under an applied pressure of 90 MPa. Tensile properties of the unreinforced AM60 alloy, Al2O3 fibre/AM60 composite, hybrid composite containing both Al2O3 fibres, and micron and/or nano-sized Al2O3 particles were evaluated. The addition of fibres and/or micron-sized particles significantly improves the ultimate tensile and yield strengths of the matrix alloy from 171 and 81 MPa to 192 and 142 MPa, respectively, while a substantial reduction (73%) in ductility from 6.0% to only 1.6% is observed. The replacement of the micron particles with the nano-sized Al2O3 particles into the hybrid composite restores the ductility from 1.6% to 3.5%. Microstructure analyses via optical (OM) and scanning electron (SEM) microscopes suggest that the homogeneous distribution, clean interfacial structure and grain refinement result in the high strengths of the magnesium hybrid nanocomposite (MHNC). The observation by transmission electron microscopy (TEM) indicates that the presence of a relatively low dislocation density in the matrix grains of the MHNC benefits the ductility restoration. The SEM fractography shows that the fracture mode of the composites is the evolution of localized damages, such as particles and fibres damage and cracking, matrix fracture, and interface debonding, which are consistent with the tensile results.