Homogenization of 7050 plates by a novel differential temperature rolling

ABSTRACT

Inhomogeneity in thickness direction has hindered efforts to produce ultra-thick aluminum plates. To overcome the challenge, we adopted a novel differential temperature rolling method by controlling the surface and the center temperature in a pre-cooling step. Compared with conventional temperature rolling, the improvement in inhomogeneity was revealed directly by tensile properties testing, hardness testing, Scanning Electron Microscope and Electron Back-Scattered Diffraction. The results show that the designed temperature field improved the deformation of the center layer. Therefore, the precipitates were rolled to be considerably smaller in the center layer. The smaller size also made it easier to dissolve the precipitate into the matrix in the following solution treatment, which improved the mechanical properties. However, the lower temperature in the pre-cooling step caused increased recrystallization, which decreased from the surface to the center and resulted in worse mechanical properties. The full effects of solution recrystallization and quenching are observed in the ultimate tensile strength inhomogeneity decrease from 9.0% to only 0.65%.

Keywords:

• Rolling
• temperature
• ultra-thick
• 7050
• microstructure
• mechanical properties
• homogenization

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [51375503]; the BaGui Scholars Program of China’s Guangxi Zhuang Autonomous Region [2013A017]; the National Basic Research Program of China [2012CB619500]; the Major State Research Program of China [2016YFB0300901].