Effect of the chemical composition of aluminium alloy EN AW-2024 on the strengthening state after T6 and T6I6 treatment.

Purpose: The work focuses on comparing three EN AW-2024 aluminium alloys with different chemical compositions within the standard limits to understand the influence of the chemical composition on the mechanical properties obtained. The study discusses the correlations between intermittent ageing processes and the improved strength, hardness, and fatigue resistance of some alloys compared to traditional aging processes. Design/methodology/approach: To understand how the chemical composition affects the mechanical properties, each alloy underwent T6I6 treatment (intermittent ageing with a weekly break) compared to traditional T6 treatment. The study involved SEM and TEM microscopic observations, as well as EDS tests to analyse the chemical composition, hardness, and uniaxial tensile testing. Findings: In the research conducted, both SEM and TEM microscopic observations revealed a similar percentage of intermetallic phase particles in the alloys. However, there were significant differences in the size and distribution of the particles. The alloy with the maximum Fe and Si content showed the highest particle refinement. Despite the observed differences in microstructure, the tests for Young's modulus, yield strength, and strength were found to be the same or very similar and were not influenced by the alloy processing process. The only notable difference in the strength parameters was the parameter marked as elongation in the direction of tension, with its lowest value observed in the alloy with the highest Si content. Research limitations/implications: The issue that arose during the analysis is accurately evaluating the alloy's morphology, particularly defining the three-dimensionality of the resulting phases using TEM. To conduct a more comprehensive analysis, additional tests need to be performed for statistical significance. In the future, SEM and TEM analyses and real-time tensile tests on specially prepared samples under the microscope would be beneficial. Practical implications: The work presented addresses whether the chemical composition of the standard area plays a crucial role in achieving consistent mechanical properties of the aluminium alloy after the ageing processes. Despite the observed structural differences, the material's mechanical properties remained unchanged. This information is valuable for process design. Originality/value: Comparison of mechanical properties, morphology, and phases formed after the ageing process of alloys of the same grade with minor differences in chemical composition. [ABSTRACT FROM AUTHOR]