MANUFACTURING PROCESS INFLUENCE ON MICROSTRUCTURAL FEATURES OF SELECTIVELY REINFORCED MAGNESIUM METAL MATRIX COMPOSITES

摘要

The mechanical and physical properties of a casting are highly dependent on the resultant microstructure. This is especially critical with metal matrix composites where the ability of the matrix to transfer load to the reinforcement is essential. Lack of load transfer resulting from poor adhesion of reinforcement to metal matrix can produce a material of little engineering value. The ability to transfer the loading through the metal matrix composite is highly dependent on favorable interfacial reactions at the reinforcement/matrix interface. An examination of three manufacturing methods and the resultant interfacial and microstructural characteristics is provided. Solidification rates play a large role in microstructural evolution in a cast component. Microstructures of cast composites have an added layer of complexity in the solidification process due to the ceramic reinforcement/metal matrix interactions. The current work suggests that solidification rates impact the grain size and structure in an MMC material. Magnesium composite samples are cast using different casting pressures and solidification rates to study the resultant microstructural differences. The samples are tensile tested and the grain size beneath the fracture surface is measured. Effects of grain size, and interfacial constituents due to the various cooling rates are analyzed using a SEM, EDS, and X-Ray Diffraction.