The role of Mg content in regulating microstructures and mechanical properties of Al–Mg–ZnO composites fabricated via in-situ reaction sintering

Abstract

Al–Mg-oxides composite system exhibits great potential for achieving aluminum matrix composites (AMCs) with exceptional mechanical properties. However, the effects of Mg element on in-situ reaction mechanism and precipitation behavior remains largely unknown. In this work, Al–Mg–ZnO composite was successfully fabricated by using segmented ball milling, reaction sintering and heat treatment, resulting in an ultimate tensile strength of ∼760 MPa and fracture elongation of ∼3.5 %. The Mg content-dependent reaction pathway and precipitation evolution were systematically investigated through thermodynamic analysis and microstructural characterization. The results revealed that the relatively high Mg content promotes the in-situ generation of the hybrid reinforcements composed of MgAl2O4 and MgO. Additionally, the semi-coherent reinforcement-matrix interface facilitates interfacial precipitation by reducing the energy barrier for nucleation. Consequently, solute-rich/vacancy-rich Guinier-Preston (GP) zones are activated to form η′ and T′ precipitates. These high-density nano-sized secondary phases contribute to the considerable strengthening effect of the composite. The present work provides valuable theoretical insight into the effect of Mg content on the microstructure evolution of Al–Mg–ZnO composite system, which offers promising avenues for achieving AMCs with superior mechanical properties.