Processing and Properties of Magnesium-Based Composites Reinforced with Low Levels of Al2O3

Lightweight structural metals such as magnesium are gaining extensive interest due to the increasing global demand for reducing greenhouse gas emissions. In order to promote the use of magnesium, its mechanical properties must be improved. Reinforcement with hard ceramic particles is an effective means for improving the properties of Mg alloys. The current study examined the effect of 1 mu m alpha-Al2O3 particles on the microstructure and mechanical properties of AZ91E Mg alloy using permanent mold stir casting. The results were evaluated through optical microscopy, scanning electron microscopy and tensile testing. Experimentally obtained tensile results were compared to theoretical strengthening mechanism models. The findings suggested that the addition of Al2O3 led to improvements in both microstructure and tensile properties. Through the addition of 1 wt% Al2O3, the grain size and yield strength improved by 61% and 11%, respectively. The highest levels of improvement for ultimate tensile strength and ductility, achieved through 0.5 wt% Al2O3 addition, were 15% and 79%, respectively. In addition, refinement of the alloy secondary phases was also observed. These findings were attributed to a combination of grain refinement and coefficient of thermal expansion mismatch between the matrix and the reinforcement particles. As well, the experimental results were in good agreement with the theoretical models sometimes affected by agglomeration of particles. This research demonstrated that the addition of Al2O3 resulted in a novel and effective method for improving the properties of Mg alloys for use in consumer electronics, aerospace applications and the transportation sector.

Automated summary

This study investigated the effect of adding 1μm α-Al2O3 particles on the microstructure and mechanical properties of the AZ91E magnesium alloy. The results showed that the addition of Al2O3 improved the grain size, yield strength, ultimate tensile strength and ductility of the alloy. The refinement of the alloy secondary phases was also observed. These improvements were attributed to a combination of grain refinement and coefficient of thermal expansion mismatch between the matrix and the reinforcement particles.