Al-Al
2O
3-MgO cast particle composites prepared by an MgO coating technique were investigated for their microstructural and mechanical property features. In all, sixteen compositions of the composite were subjected to this study. Generally, a uniform distribution of Al
2O
3 particles was observed in the composites. But in the upper half portion of the cylindrical castings, Al
2O
3 particles were found to segregate along the grain boundaries and also within the grain-forming chain-like structures. The microhardness of the base matrix revealed that the retention of submicrometre MgO particles causes dispersion strengthening. In the case of maximum strengthening, the microhardness of the base matrix rises to 35 kg mm
–2 from 19 kg mm
–2 for as-cast pure aluminium. The composites also displayed excellent high-temperature tensile properties up to 250°C (523 K). At the level of 21%
V
f retention of Al
2O
3, the composite displayed a UTS value of 110 MN m
–2 with corresponding 0.2% offset yield strength of 65 MN m
–2 and 12% elongation at ambient temperature. At 150° C (423 K) and 250° C (523 K), the composite retains 69% and 53%, respectively, of its room-temperature UTS value. This was the optimum retention of Al
2O
3 and the best composite obtained in the present work. The excellent high-temperature characteristics of the composite are thought to be due to the sum total effect of both the submicrometre MgO particles and the coarser Al
2O
3 particles retained in the aluminium base matrix.
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