The Effect of La-intermetallic Compounds on Tensile Properties of Al-15%Mg2Si In-situ Composite

In this work, an attempt was made to examine the effect of different La-intermetallic on the microstructure and tensile properties of Al-15%Mg2Si metal matrix composite (MMC). The composite was made via in-situ process and characterized by optical microscope (OM), scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis. Microstructural characterization revealed that La changes not only the morphology of primary Mg2Si particles from irregular to polyhedral and cubic shape. But also alter the eutectic Mg2Si phase from flakes to rods and the volume fraction of Mg2Si decreases while volume fraction of α-Al phase increases. La addition change the size of primary Mg2Si from (∼17 μm) to (∼10 μm) and the size of eutectic Mg2Si phase is reduced from more than 4.0 μm to less than 0.5 μm. This is mainly due to the formation of LaSi2 phase during solidification, as detected by XRD analysis. Further results revealed that as the amount of fine La-intermetallic is increased, ultimate tensile strength (UTS) and elongation values of the MMC were also significantly increased. The fracture study of the composite showed the La-intermetallic changes the mode of fracture from brittle to more ductile.