Microstructures and Properties of Diffusion Layer Formed at Laminated Interface of Alumina-Particle Dispersed Magnesium Laminated Compacts Fabricated by MM/SPS Method

20/0/20vol% Al2O3/Mg laminated spark plasma sintering compacts (20/0/20vol% laminated SPS compacts), which were fabricated by mechanical milling / SPS method, have proved to possess lightweight like that of general practical Mg alloys and higher surface hardness than them. Moreover, the diffusion layer formed at their 0/20vol% layer interface has been found to exhibit high adhesion to the 20 and 0 vol% layers. The microstructures and the properties of diffusion layer were investigated using XRD, EPMA, TEM-EDS and so on. From the results of XRD, the constitutive phases were identified as αMg and MgO. Moreover, from the results of EPMA and TEM-EDS microstructure observation and elemental analysis, it was estimated that the microstructures were composed of reticulate MgO and in the MgO, Mg-Al solid solution αMg, fine needle-like Mg17Al12 and fine MgO particles. The cross-sectional hardness was 145 to 155 HV and was higher than that of the general practical Mg alloys. The width grew almost linearly rather than parabolic with sintering time. It is considered that the solid-state reaction of Mg and Al2O3 proceeded with sintering time, the amount of Al decomposition from Al2O3 increased, resulting in an increase in Al diffusion.