This research aims to compare the surface roughness of AA7178 reinforced with 5% fly ash and 5% nano zirconium oxide (ZrO₂) hybrid composites fabricated using a novel encapsulation process to that of as-cast AA7178 alloy. Group 1 consists of AA7178 as-cast samples without any composite material, whereas group 2 comprises AA7178 metal matrix composite prepared using a hybrid composite of fly ash (5%), nano ZrO₂ (5%), and AA7178. The samples for both groups are fabricated by stir casting using a novel encapsulation technique. The samples of both groups were created by following the ASTM E92 guidelines, and a Mitutoyo surface roughness tester (SJ-410) was used to measure the sample’s surface roughness. The G-power used for this process is 80%, α = 0.05 per set for calculating sample size and the total sample size is 40; each group contains 20 samples. The samples filled with reinforcement of (5% and 5%) fly ash and nano ZrO₂ exhibit a more excellent surface finish than samples of as-cast AA7178 without any reinforcement. Based on t-test statistical analysis, it is obtained that there is a significant p = 0.00 (p < 0.05) difference between group 1 and group 2 in the mean variance of surface roughness. Within the limitations of this study, it proves that the reinforcement of AA7178 with 5% fly ash and 5% nano ZrO₂ considerably decreases 29.90% of surface roughness compared to as-cast AA7178 alloy.

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