ABSTRACT
In the research of Kok (2005) 2024 Al alloys reinforced with Al2O3 particles in three different sizes of 16, 32 and 66 μm at weight fraction of 10 wt%, 20 wt%, 30 wt% was fabricated by a Vortex method or Stir casting (adding Al2O3 particles in the stirred Al alloy molten under the argon gas atmosphere) which it was a simple and inexpensive processing method in Figure 1 and subsequent casting with pressure e.g. sand or squeeze casting. As a result, the dispersion of coarse particles in composite was more uniform than that of fine ones. The composite with finer particles took place particle agglomeration and porosities and the hardness and the tensile strength of composites increased with decreasing alumina size and increased with increasing weight fraction of alumina. In work of Bhansali & Mehrabian (1982), Al MMC reinforced with Al2O3 was found to be superior to those containing SiC in abrasive wear resistance. This difference in wear resistance was
caused by the formation of silicon oxide, a brittle bonding layer at Al alloy/SiC interfaces. When compared at the same weight fraction of alumina (20 wt%), the wear resistance of composite with micro-scale Al2O3 (142 μm) was better than those containing smaller Al2O3 particles (63 μm, 16 μm). The hardness values of the composite with Al2O3 particle in size of 142, 63, 16 μm were 70, 66, 52 HRB respectively. The alumina particles of these casted composites were uniformly distributed in the metal matrix as shown in Figure 2.
