Influence of heat treatment on the fatigue behaviour of two aluminium alloys 2024 and 2024 plated

摘要

In the present work, the influence of the heat treatment on the evolution of oligocyclic fatigue life on two types of aluminium alloys was studied. The two alloys (2024 and 2024 plated by 1050) are largely used in the aircraft industry because of their good mechanical characteristics and their lightness. The main factor of heat treatment influencing fatigue behavior in these two types of alloys is the precipitation of Al2Cu in the 2024 alloy and diffusion of cupper from the middle to the surface in the 2024 plated one. Our work is to locate the effect of heat treatments on different microscopic characteristics and their influence on the evolution fatigue damage, the idea of using heat treatments is based on their role to change the precipitation and the direction of diffusion on those alloys. The results obtained showed that we can increase the fatigue performance in 2024 alloy of about 34 % just by using different age hardening, so this process of age hardening can be envisaged to increase the fatigue life of aluminium components when these are submitted to fatigue loading, however, in the case of 2024 plated alloy, the diffusion phenomenon has made their surface very fragile, what led to the reduction in their lifespan. Microstructural investigations, such as scanning electron microscopy and micro hardness, were carried out in order to observe the microstructural evolution due to heat treatment and fatigue.