Grain Refinement of 7475 based Aluminum Alloy Sheets by Warm Rolling with Heated Rolls and Its Effect on Texture and Mechanical Properties

摘要

The effect of temperature of the rolls in the range from 2 deg C to 110 deg C in the warm rolling process was investigated in order to refine the structure of the 7475 based aluminum alloy sheets including Zr. It was found that lower temperature of the rolls led the alloy sheets to coarser grain structure after solution heat treatment. The {100} Diagonal Cube component appeared in the surface layer, which suggested that strong shear bands had been formed during the warm rolling in the layer. It was thought that these shear bands acted as nucleation sites for the recrystallized grains in solution heat treatment and contributed to the development of the coarse grain structure in the surface layer. Regarding the center region, low temperature condition on the rolls did not cause sufficient plastic deformation because of the cyclic occurrence of hardening and softening at the surface layer in the warm rolling process. Consequently, the center region also became coarse grain structure after solution heat treatment. On the contrary, in the case of a higher temperature of the rolls, the subgrain structure less than 3 mum was formed uniformly through the thickness of the plates after solution heat treatment with the strong Brass texture component. The warm-rolled sheets consisting of fine grain structure had a high Lankford value in 45 deg to the rolling direction.