Preparation and mechanical properties of in situ submicron MgAl2O4p/6061Al composites from Al–Mg–SiO2 system

Abstract

In situ MgAl2O4p/6061Al composites were prepared by a combination of ball milling, hot rolling, and ultrasonic assisted direct melt reaction (DMR) process. The results showed that submicron SiO2 could be reacted to form bimodal type sized MgAl2O4 particles with nano and submicron size in an Al–Mg alloy melt. The grain refinement achieved by the in situ formed MgAl2O4 particles in the matrix alloy. With the increase of in situ MgAl2O4 particles content from 0.0 wt% to 2.0 wt%, the grain size of MgAl2O4p/6061Al composites decreased from 272.3 μm to 74.4 μm, and the morphology of α-AlFeSi phases changed from a coherent Chinese-script morphology to a relatively single particle type. Through HRTEM studies and detailed crystallographic analysis, it was confirmed that the dispersed MgAl2O4 particles may serve as effective heterogeneous nucleation sites for both the α-Al and α-AlFeSi phases. The composites contained 2.0 wt% reinforcements exhibited the best comprehensive mechanical properties, and the yield strength, ultimate tensile strength, and elongation were improved by 45.8%, 51.3%, and 14.5%, respectively.