Effect of chemical composition on the microstructure and hardness of Al–Cu–Fe alloy

Four Al–Cu–Fe alloys with compositions; a) Al65Cu20Fe15, b) Al64Cu22.5Fe13.5, c) Al61Cu26Fe13 and d) Al62Cu25.5Fe12.5, where the icosahedral phase is present, have been experimentally studied in both as-cast and annealed conditions in order to investigate the effect of chemical composition on the percentage of icosahedral phase and the changes in hardness of the alloy and each phase. It was found that the a) Al65Cu20Fe15 and b) Al64Cu22.5Fe13.5 alloys, which present the highest Fe content, showed the largest amount of λ-Al13Fe4 phase as well as the highest hardness in all phases. In contrast, the same alloys developed the lowest amount of icosahedral phase after heat treatment. The c) Al61Cu26Fe13 and d) Al62Cu25.5Fe12.5 alloys had a better response to heat treatment, reaching amounts of icosahedral phase up to 87% and 99% respectively. The hardness of phases after heat treatment increased with respect to alloys in as- cast condition, the hardness of icosahedral phase increased between 20% and 25%, while the hardness of λ-Al13Fe4 phase increased 9%. The icosahedral phase of annealed a) Al65Cu20Fe15 alloy was the toughest with a hardness value of 844HV.

► The D) Al62Cu25.5Fe12.5 alloy in cast condition had the highest amount of icosahedral phase.
► Alloys with higher Cu content and lower Fe content had a better response to heat treatment.
► The amount of icosahedral phase increased after heat treatment up to 87 and 99%.
► The hardness of icosahedral phase increased after heat treatment between 20% and 25%.