Abstract: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 Al₃TiSi_0.22 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.

Key words: 6351 Al alloy; microstructure; in situ particle reinforced aluminum composites; electromagnetic stirring; fluxes