Microstructure of in situ Al_3Ti/6351Al composites fabricated with electromagnetic stirring and fluxes

The 6351 wrought aluminum alloy and K2TiF6-CaF2-LiCl components were selected as raw materials to fabricate in situ Al3Ti particulate reinforced aluminum alloy at 720 ℃ via direct melt reaction method with electromagnetic stirring (EMS). CaF2 and LiCl acted as fluxes to lower the reaction temperature of the system. It is shown that the electromagnetic stirring and fluxes accelerate the emulsion process of K2TiF6. Optical microscopy, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrum were utilized to analyze the microstructure and components of composites. Compared to composites fabricated without EMS and fluxes, the sizes of endogenetic Al3Ti are refined from 10-15 μm to 2-4 μm, which are often accompanied with silicon element. The morphology of Al3Ti or Al3TiSi0.22 exhibits triangle, quadrilateral and other clumpy patterns. Because of the Ca elements from CaF2, the sizes of Mg2Si decrease from 8-10 μm to 1-2 μm due to the formation of Ca2Si.