Effects of Natural Aging Treatment on Mechanical, Microstructural and Forming Properties of Al ۲۰۲۴ Aluminum Alloy Sheets

In this study, the microstructural variations, mechanical properties and forming limit diagrams (FLD) of Al ۲۰۲۴ aluminum alloy sheet with the thickness of ۰.۸۱mm are investigated during natural ageing (T۴) treatment. The most formability in Al ۲۰۲۴ can be achieved just after solution treatment, and it is better to perform the forming process, on this aluminum alloy sheet, in this condition. However, in industrial applications, there is usually a postponement for some hours after solution treatment to begin the forming process that it means the forming process should be done at the natural ageing condition. This condition decreases the formability of Al ۲۰۲۴ sheets. To monitor the properties variations in natural ageing condition, FLDs are determined after specific times (e.g., ۰.۵, ۱.۵, ۴ and ۲۴ hours). The variations in micro-hardness, yield strength, ultimate tensile strength and elongation at break are observed with changing the ageing time. The scanning electron microscope (SEM) investigations illustrated that density and size of precipitates are changed with ageing time. Moreover, the Nakazima test is utilized to study the forming limits considering the natural ageing condition. Results show by increasing the ageing time, up to ۴hr, the majority of properties variations could be seen, and from ۴hr to ۲۴hr, the variations are changed slower.

کلیدواژه ها:

Aluminum alloys ، Natural aging ، Solution ، Forming limit diagrams