The effect of heat treatment and strain rate on the mechanical behaviour of aluminium alloy 2024
摘要
Currently a reduction of carbon emissions is one of the key things in the automotive industry. Thanks to the development of aluminium alloys, which possess favorable weight to strength ratio the reduction can be performed. Therefore, this study is focused on the mechanical behaviour and formability of the heat-treated AA2024 in sheet form with a thickness of 1 mm, which was tested under different strain rates. The microstructure in as-received (T3) state exhibited a tendency to create preferential orientation along the rolling direction. The grain size yielded an 4.9 % and 4.4 % increase in longitudinal and transverse planes after heat treatment (solution treatment and water quenching), respectively. The microstructure of AA2024-T3 consisted of numerous Al-Cu-Mn-Fe and Al-Cu-Mn precipitates, which corresponded to higher mechanical properties. The mechanical behaviour tested imminently after heat treatment manifested by yield strength decrease of 52.3 % under strain rate 0.0008 s–1 and 54.8 % under strain rate 0.18 s–1, respectively. This phenomenon was caused by dissolution of precipitates and oversaturating α matrix with alloying elements. The heat-treated material featured a negative strain rate sensitivity, phenomenon that can be attributed to dynamic strain aging, which was further confirmed by the presence of the Portevin-Le Chatelier effect.