Influence of initial microstructure on texture and earing in aluminium sheet after cold rolling and annealing

Abstract

Achievement of good formability in aluminium sheet requires control of the final texture. Earing in deep drawing is a common problem in aluminium sheet and can be minimised by careful texture control. In practice, this means the control of recrystallisation during thermomechanical processing as well as control of particle size distributions and elements in solid solution within the material. Experiments have been carried out using aluminium alloyed with various amounts of iron and silicon. The alloys were characterised in terms of the size distributions of second phase precipitates and elements in solid solution. The materials were hot rolled at a rather low final temperature which resulted in a deformed structure after coiling. They were then heat treated to give different amounts of recrystallisation before further cold rolling and annealing. Earing measurements were made following a wide range of cold reductions in both cold rolled and annealed states. Texture development and recrystallisation behaviour were studied carefully in a few selected samples. The results showed that the presence of second phase iron rich particles is a dominant factor governing the texture and earing behaviour. Furthermore, it is of the utmost importance to control the hot worked structure before cold rolling and annealing. The reasons for this are discussed in more detail using well known theories for nucleation of recrystallised grains considering particle size distributions, deformed microstructure, and elements in solid solution.MST/1366