Effect of Heat Treatment Parameters on Hardness of Al–Fe Alloy Mixed with Recycled Aluminum Cans

This research investigated the effect of factors on the hardness of hypereutectic Al-Fe alloys mixed with 75 wt% recycled beverage cans, which are treated by a heat-treatment process. The hypereutectic Al-Fe alloy is a new and interesting aluminum alloy that combines aluminum (Al) and iron (Fe) and exhibits good compatibility. The mixed cans also contain alloying elements such as magnesium (Mg), manganese (Mn), silicon (Si), copper (Cu), and more, strategically chosen to enhance the alloy's mechanical properties. As the proportion of these alloying elements increases with the mixed cans, the 75 wt% recycled beverage cans are crucial in revealing the influence of minor alloying elements on the alloy's structure and properties. Notably, elements like Mg, Si, and Cu have the potential to enhance hardness through heat treatment. Following casting, the samples were analyzed, revealing the following composition: 94.27wt% Al, 3.81wt% Fe, 0.81wt% Mg, 0.52wt% Mn, 0.33wt% Si, 0.14wt% Cu, and other elements at 0.12wt%. In this experiment, a 24 full factorial design was used, consisting of a total of 4 factors (solution heat treatment temperature (SHTTemp), solution heat treatment time (SHTTime), aging temperature (AgingTemp), aging time (AgingTime)) at two levels. The factors included SHTTemp at 460 and 560 ºC, SHTTime at 1 and 4 hours, AgingTemp at 150 and 200 ºC, and AgingTime at 2 and 8 hours. The response variable is the Brinell hardness (HB) and this experimental set was utilized by using the principle of analysis of variance (ANOVA) for the result analysis. The results indicated that the factors significantly affecting the hardness with a confidence level of 95% are the aging temperature and aging time. Due to the addition of magnesium and silicon components from the aluminum alloy by mixing with recycled beverage cans, the precipitation of fine particles of Mg2Si occurred within the aluminum matrix during the aging process. This precipitation hardening contributes to enhancing the hardness of this alloy. Furthermore, statistical analysis revealed that both the solution heat treatment temperature and time were found to be statistically insignificant factors in influencing the hardness of this alloy. The optimized significant factors resulted in the increase in hardness from 49 HB to 57 HB after testing at a solution heat treatment at 560 ºC for 1 hour and aging at 200 ºC for 8 hours.