Effect of Alumina Content on the Mechanical Properties of Alumina Particle Dispersion Magnesium

To enhance the mechanical properties of magnesium (Mg) alloys, powders of pure Mg (Al2O3/Mg) dispersed with over 10 vol% alumina (Al2O3) particles were made by ball milling powder mixtures of pure Mg and Al2O3 particles with particle sizes of 0.3 and 1 μm. The effect of the Al2O3 content of hot-pressed discs formed from the Al2O3/Mg powders on the mechanical properties of the discs was investigated. The Al2O3 particles were found to be uniformly dispersed in the Al2O3/Mg discs. The hardness of the discs increased sharply at an Al2O3 content of 20 vol%. This is considered to be because of the excellent interfacial bonding between Mg and Al2O3 when the Al2O3/Mg discs contain a sufficient amount of Al2O3 particles and have a sufficient interparticle distance. The maximum hardness of a 20 vol% Al2O3/Mg disc (with an Al2O3 particle size of 0.3 μm) was 220 HV, which is much higher than the hardness of AZ91 Mg alloys. The bending strength of the Al2O3/Mg discs increased from 0 to 10 vol% Al2O3 and then decreased from 20 vol% Al2O3. It is considered that the 0 and 10 vol% discs have similar fracture deflections and that the 10 vol% discs with Al2O3 particles can withstand higher compression and tension forces than the 0 vol% discs which do not contain any particles. The reason for the lower bending strength of the 20 vol% Al2O3 disc is thought to be because it is harder and more brittle, making it easier for voids to form in the discs, and thus making it easier for cracks to propagate on the specimen surface.