ASSESSING MICROSTRUCTURE AND MECHANICAL BEHAVIOUR OF Al-15% Mg₂Si IN-SITU COMPOSITE WITH CONCOMINENT ADDITION OF PRASEODYMIUM AND ANTIMONY

Abstract

Aluminium alloys offer a high strength-to-weight ratio, excellent corrosion and oxidation resistance and significant energy absorption during collision, improving vehicle safety. To strengthen the performance of aluminium-cast alloys, aluminium matrix composites with Mg₂Si reinforcement have been developed. They are consistently promising materials for industries like aerospace and automotive due to their higher specific strength. However, the large size and dendritic morphology of primary Mg₂Si occur in the structure of the unmodified Al-Mg₂Si alloy during solidification, causing the mechanical characteristics of the alloy to deteriorate. This study aims to modify and refine the primary Mg₂Si phase with Pr-Sb simultaneous alloying with varying weight percentages. Hence, the microstructure and mechanical properties were examined with the Al-15% Mg₂Si with the simultaneous addition of Pr and Sb. Optical microscopy and SEM/EDS were used to study microstructure. The region with the smallest average particle size exhibited the maximum density of the Mg₂Si phase, the greatest tensile strength (108.01 MPa vs 84.61 MPa) with elongation (9.42% versus 5.68%) and a hardness value of 58.50 HV was achieved by simultaneously introducing 0.5 wt.% Pr-Sb to the composite compared to the base Al-15% Mg₂Si composite. It was proposed that modification of primary Mg₂Si particles was mainly derived from the formation of Mg₃Sb₂ compounds as heterogeneous nuclei for primary Mg₂Si. Meanwhile, the absorption and poisoning of Pr and Sb can suppress the preferred growth of primary Mg₂Si crystals along <100> direction. Hence, the results showed that the simultaneous addition of Pr and Sb improved the microstructure and mechanical properties of the Al-15% Mg₂Si composite by making the primary Mg₂Si particles finer.