Fabrication of Vapor-Grown Carbon Fiber-Reinforced Magnesium-Calcium Alloy Composites by Compo-Casting Process

摘要

Magnesium-calcium alloy composites reinforced with nickel-coated vapor-grown carbon fibers (VGCFs) were fabricated using a compo- casting process. Then, the microstructures and mechanical properties of these composites were investigated. The Mg-5Al-3Ca (AX53) alloy exhibited a dendritic microstructure with a coarse lamellar (Mg, Al)(2)Ca phase along the grain boundaries instead of the irregular beta-Mg17Al12 phase found in the Mg-5Al alloy. For the 0.5% Ni-coated VGCF-reinforced AX53 alloy composite, the VGCFs were well dispersed in the matrix, with the nickel coating diffused into the metal. Al3Ni compounds formed both inside the grains and on the grain boundaries. The ultimate tensile strength (UTS) and strain-hardening of the AX53 alloy, in comparison with the Mg-5Al alloy, were improved significantly to the point of fracture. Furthermore, an increase in the UTS of the composite was achieved with the addition of 0.5% VGCFs, along with an increase in the total elongation, which could mainly be attributed to the strain hardening during a larger strain. The 0.2% yield stress was slightly improved as a result of the small amount of introduced Ni-coated VGCFs. However, the elongation dropped for the 1.0% VGCF-reinforced AX53 alloy composites, which led to a low strength similar with that of the AX53 alloy.