Fabrication of Laminated Spark Plasma Sintered Compacts Composed of Alumina-Particle-Dispersed Magnesium and Magnesium

Abstract

To reduce the weight of 20 vol% Al 2 O 3 -particle-dispersed Mg (Al 2 O 3 /Mg) compacts produced by spark plasma sintering (SPS), which are much harder than practical high strength AZ91 Mg alloys, 20/0/20 vol% laminated SPS compacts sandwiching a lightweight 0 vol% Al 2 O 3 /Mg (0 vol%) layer between two 20 vol% Al 2 O 3 /Mg (20 vol%) layers were fabricated by a mechanical milling/SPS process, and their microstructures and mechanical properties were investigated. The density of the 20/0/20 vol% laminated SPS compacts was 1.88 Mg·m , and they could be lightened to approximately 80% of the weight of equivalent 20 vol% SPS compacts. The 20/0/20 vol% laminated SPS compacts had a slightly higher hardness than the 20 vol% SPS compacts and a much higher hardness than AZ91 alloys. The bending strength of the 20/0/20 vol% laminated SPS compacts was almost the same as that of the 20 vol% SPS compacts, and was higher than the value calculated from those of the 20 and 0 vol% SPS compacts using the rule of mixtures. A new phase appeared at the at interface between the 20 and 0 vol% layers with excellent adhesion to the adjoining layers, so this phase probably had a strong effect on the bending strength of the 20/0/20 vol% laminated SPS compacts. The new phase generated a monotonically decreasing hardness gradient from the 20 vol% layer to the 0 vol% layer and was formed by diffusion of Al and O from the 20 vol% layer and diffusion of Mg from the 0 vol% layer. The new phase most likely consisted of αMg, MgO, and Mg 17 Al 12 , and the concentrations of Al in the αMg, MgO, and Mg 17 Al 12 components of this phase were considered to decrease from the 20 vol% layer to the 0 vol% layer.