Control of annealing texture and earing in non-hardenable aluminium alloys

Abstract

Factors affecting textures in non-hardenable aluminium alloys are considered on the basis of published results and some new experimental results. Emphasis is placed on conditions relevant to industrial scale rolling and annealing of sheet products. The most commonly observed texture components in these alloys are summarised, together with available evidence regarding their origins. Hot rolling conditions have a powerful effect on subsequent annealing textures, which is attributed to the microstructural state of the material before cold rolling. This can influence the relative frequency of different nucleation mechanisms. Heat treatment of the hot rolled band can also bring about marked changes in texture and earing for the same reason. The effect of cold rolling reduction on texture is complex and depends on the initial microstructure; increasing reduction promotes an increasingly heterogeneous substructure. The main impurity in these alloys is iron, which plays several different roles in controlling texture and earing level. Iron, both in solid solution and as coarse precipitates, can weaken the cube texture and promote 45° earing tendency. However, fine scale precipitation in the deformation substructure before recrystallisation may contribute to a strengthening of the cube texture. For high contents of iron and heavy rolling reductions, where continuous recrystallisation occurs, the rolling texture is retained or may even become strengthened. Influences of silicon, manganese, and magnesium are also discussed.

MST/1295