Title: The effect of particle content and sintering time on the properties of Al Al9Co2-Al13Co4 composites, made by powder metallurgy

Abstract

In the current study, aluminum matrix composites made of Al-Al9Co2-Al13Co4 are developed using powder metallurgy with a flow of N2 at a temperature of 600°C. In this study, the impacts of process variables such cobalt concentration (0.5, 1, 3, and 5%at.) and sintering time (4, 8, 24, 48, and 72 hours) on hardness were examined. X-ray diffraction analysis, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy were used to evaluate the crystalline phase and microstructure of the composites made using the powder metallurgy process. A micro-Vickers hardness tester was used to test the mechanical properties. During heat treatment, mixed products Al13Co4 and Al9Co2 were generated in the aluminium matrix through reactive diffusion in solid state. The results show, on the one hand, that the obtained alloys have microhardness values that are significantly higher than those of pure aluminum (49 ± 4 HV). In contrast, the microhardness of alloys based on the compositions ‘Al-0.5% Co’ and ‘Al-1%Co’ increases with the sintering time and achieves a maximum value of 153.89 ± 4.85 HV and 141.49 ± 7.81 HV, respectively, at a sintering time of 72h. Nevertheless, the microhardness decreases with longer sintering times of 72h for the higher compositions that were studied ‘Al-3%Co’ et ‘Al-5%Co’. After 48 h of sintering, the microhardness of the ‘Al-3% Co’ alloy falls from 131.88 ± 2.50 HV to 102.67 ± 4.33 HV. For the alloy ‘Al-5%Co’, it decreases from 93.87 ± 2.50 HV to 64.65 ±2.50 HV after 24 h of sintering. This decrease in hardness is explained by the generation of a large amount of pores during the sintering of the alloys with large compositions. The electrochemical behavior of these composites was studied in this work.