Abstract. As a matrix, aluminum has been widely studied because of its wide range of applications and outstanding properties. Scientists of material science usually face some challenges regarding the mechanical and tribological properties of aluminum because of its poor behavior with respect to these aspects. Therefore, the main objective of this work is to enhance the corrosive resistance and mechanical properties of aluminum by strengthening it by the addition of nickel and aluminum oxide through stir casting by using the vortex technique. Al-Ni-Al2O3 composition was prepared by adding a fixed value of Ni (20%) and mixed with different values of Al2O3 for a range of (4-8%) within 2 wt.% increments. The vortex technique was used for the stir casting required for the composite material preparation. It is noted that increasing of Al2O3 percentage increases the hardness of the composite of the aluminum matrix. The maximum increment of the hardness values (about 55%) was found at 8% Al2O3 composite. The erosion-corrosion, general corrosion for the alloy of Al-20%Ni base, and the prepared composite material were achieved within 3.5wt% NaCl solution used as a corrosive medium for the general corrosion. Whereas, for the erosion-corrosion at 90° as the impact angle, the slurry solution (1wt%SiO2 sand in 3.5wt% NaCl solution as the erodent) was used. It was noted that the rate of the general corrosion of the specimen of the composite is smaller than that corresponding to the base alloy (Al-20%Ni). Regarding the results of the erosion-corrosion, the resistance of erosion-corrosion of the composite was enhanced considerably with increasing Al2O3 percentages values. A noticeable improvement in the resistance of corrosion of the aluminum composite as compared to the pure aluminum specimen was noticed due to the effect of nickel addition. However, the rate of corrosion was declined with increasing the percentage of Al2O3. The great reduction of this rate was 26% (measured by mpy) noticed at 8% Al2O3 composite. In addition, this value was smaller than that corresponding to the base alloy.
Conclusions This study optimized the composites fabricated from 4% Ni and 4, 6, & 8% of Al2O3 particle as a reinforcement within the base matrix of pure aluminum using stir casting. The hardness of the Al 20% Ni matrix composites showed an increasing trend with increasing the content of Al2O3; a maximum increase of 55% was obtained for samples fabricated from 8% Al2O3 composite. There was a noticeable decrease in the general corrosion rate or weight loss rate of the composites compared with pure Al owing to the existence of Ni. Furthermore, the increase in Al2O3 content decreased the general corrosion rate in 3.5 wt% NaCl solution for 20 hours at a 2-hour cycle. The corrosion rate or weight loss rate increased continuously with the immersion time for base alloy and composite specimens. The erosion-corrosion rate in slurry solution (1 wt.% SiO2) in 3.5 wt% NaCl solution is decreased with the addition of Al2O3 particles by 14%, 20%, and 26% for specimens of 4, 6, & 8% Al2O3, respectively. In erosion-corrosion media, the removal of material was attributed to the combined effect of corrosion and erosion; therefore, the weight loss rate was significantly higher.