Abstract Two Zn–27Al–3Cu–3Al 2O 3 (wt.%) composites with different particle size (approximately 12 and 250 μm) of Al 2O 3 powder were produced by a compocasting process, i.e. Al 2O 3 particles were continuously added to a semi-solid melt which was vigorously stirred. Comparative investigations of microstructure [scanning electron microscope (SEM), energy dispersive spectrometry (EDS)] and compression strength (from room temperature to 170 °C) of as-cast alloy and composites were carried out. Composites exhibit higher strength than the as-cast alloy. The strengthening effect of smaller Al 2O 3 particles is more pronounced than the effect of much larger particles.