Fabrication conditions and microstructures of Al₁₈B₄O₃₃/AZ91D magnesium alloy composites by compo-casting

The effects of stirring condition and setting position of reinforcements on pore content in the composites fabricated by compo-casting process were investigated by the visualized model experiments using glycerin. Gas pores were introduced in composites by stirring blade and gas contained in as-received reinforcement particles. The distance between blade and liquid surface, the rotational speed of blade and the viscosity of matrix affect the entrapping of gas. Particles were mixed with matrix material completely by placing on the bottom of die. Then, Al₁₈B₄O₃₃ particle and whisker reinforced AZ91D magnesium alloy composites were fabricated by the compo-casting under the condition acquired from the visualized model experiments. The reinforcements in the composites fabricated under the condition of 33% solid fraction were distributed uniformly. Refining of primary crystal and homogenous microstructure were acquired by using AZ91D chips as a starting material or whiskers as the reinforcement.