The Effect of ZrO2 Addition and Thermal Treatment on the Microstructure and Mechanical Properties of Aluminum Metal Matrix Composites (AMMCs)

Abstract

Aluminum metal matrix composites (AMMCs) were obtained using the stir-casting method, adding 0.15, 0.25, and 0.50 in vol.% of ZrO2. Microstructural observations made using scanning electron microscopy (SEM) indicated that oxide addition modified grain size. X-ray diffraction analyses revealed that mainly ZrAl3 and Al2O3 phases had formed. Hardness evaluation indicated a maximum value of 63 HV for the zirconia-reinforced samples, representing an increase of approximately 70% compared with pure aluminum. This hardness increase was mainly attributed to the zirconia distribution in the aluminum matrix promoting lattice distortion, which promoted the inhibition of dislocation mobility. Wear tests indicated that the samples with 0.50 vol.% of ZrO2 added presented the lowest wear rate because of the hardness they acquired. The results are discussed considering composite strengthening due to ZrO2 addition and the thermal treatment applied (cooling rate).