アルミナ粒子分散マグネシウムの機械的性質に及ぼすアルミナ含有率の影響

Abstract

To enhance the mechanical properties of magnesium (Mg) alloys, powders of pure Mg (A1 2 03/Mg) dispersed with over 10 vol% alumina (Al 2 O 3 ) particles were made by ball milling powder mixtures of pure Mg and Al 2 O 3 particles with particle sizes of 0.3 and 1 μm. The effect of the Al 2 O 3 content of hot-pressed discs formed from the A1 2 03/Mg powders on the mechanical properties of the discs was investigated. The Al 2 O 3 particles were found to be uniformly dispersed in the Al 2 O 3 /μg discs. The hardness of the discs increased sharply at an Al 2 O 3 content of 20vol%. This is considered to be because of the excellent interfacial bonding between Mg and A1 2 0 3 when the Al 2 O 3 /μg discs contain a sufficient amount of A1203 particles and have a sufficient interparticle distance. The maximum hardness of a 20vol% Al 2 O 3 /Mg disc (with an Al 2 O 3 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 A1 2 03/Mg discs increased from 0 to 10vol% Al 2 O 3 and then decreased from 20vol% Al 2 O3. It is considered that the 0 and 10vol% discs have similar fracture deflections and that the 10 vol% discs with Al 2 O 3 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% Al 2 O 3 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.