The influence of grain structure and texture on formability and toughness of extruded aluminium alloys

The main focus in this work is to investigate the effect of crystallographic texture, grain structure and dispersoids on formability and toughness in some industrial 6xxx and 7xxx series alloys. Materials of these alloys showing strong cube textures or beta-fibre deformation textures in as extruded condition have been compared with the same alloys processed by rolling and heat treatment to obtain a random texture. It is found that the formability depends on the temper and the texture and that the effect of the latter is path dependent. Materials with a random texture have a significant higher formability in terms of uniform elongation than materials with cube texture when deformed in the W-temper condition. Forming in other deformation modes shows less difference between the cube and random texture. However, a fibrous grain structure with a sharp beta-fibre texture shows an anomalous behaviour when deformed in the biaxial deformation regime. Toughness, in terms of Charpy energy and local strains in the necking area, is significantly higher for materials with a cube texture as compared to materials with random textures. This difference is explained by variations in the dispersoid levels, grain structures (size and grain boundary misorientation) and the texture.