Abstract
The evolution of crystallographic texture during the thermo-mechanical processing of aluminium sheet is accompanied by the development of plastic anisotropy and, most notably, the well-known earing phenomenon. In the present paper we analyse the formation of texture and earing properties in sheets of the Al-Mg alloy AA 5050A (ISO AlMg1.5(D)) along a process route resulting in temper H16 after cold rolling and temper H44 after lacquering. This process route, which is characterized by interannealing in combination with a mild final temper rolling pass, was established for the production of Al packaging sheet with medium strength and very good earing properties. Besides a detailed characterization of the development of microstructure, texture and resultant earing properties during standard processing, measures to improve the earing properties by adapting the ratio of the relevant rolling and recrystallization texture components are addressed.
Highlights
Aluminium alloy AA 5050A (ISO AlMg1.5(D)) is a medium strength Al alloy with about 1.5% Mg which is used in household applications, as tubes for automotive gas and oil lines, welded irrigation pipes and in several packaging applications [1]
Cold rolling to an intermediate gauge of 0.61 mm led to a further refinement of the elongated band structure (Fig. 2(b)), in that the thickness of the deformed bands in the through-thickness direction was significantly reduced
In the present study it is demonstrated how texture control can be applied during industrial processing of Al alloy AA 5050A sheet in order to minimize earing through the interplay of rolling and recrystallization with the resulting textural effects
Summary
Aluminium alloy AA 5050A (ISO AlMg1.5(D)) is a medium strength Al alloy with about 1.5% Mg which is used in household applications, as tubes for automotive gas and oil lines, welded irrigation pipes and in several packaging applications [1]. Like all the AA 5xxx-series Al-Mg alloys, the strength of AA 5050A can be increased by cold working, typically by cold rolling, to the strain-hardened tempers H1x. Work hardening of Al alloy sheet is commonly accompanied by the formation of significant plastic anisotropy. It is well documented that plastic anisotropy, including the wellknown earing phenomenon, is attributed to the formation of preferred crystallographic orientation, or texture, during the thermo-mechanical production of the sheet [2,3,4,5]. The characteristic earing profiles of deep drawn cups form because the sheet texture gives rise to different radial elongations in different directions of the blank. In a rolled Al sheet with a pronounced deformation texture the ears are usually observed at the four positions ±45° to the rolling direction around the drawn cup. In the soft annealed, recrystallized state ears are often found at angles of 0° and 90° to the former rolling direction
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