Abstract: Recrystallization behavior under different conditions (different temperatures and times) of AA 7075 alloy processed by new short-cycled thermo-mechanical processing was investigated to design a suitable recrystallization schedule. With acquiring recrystallization activation energy by DSC, the recrystallization behavior was successfully verified by theoretical calculation. Experimental results of recrystallization response and re-dissolution of precipitates during isothermal annealing reveal excellent agreement with DSC prediction. The results show that the obtained activation energy of recrystallization can be used to establish the relationship between recrystallization temperatures and times. It is proposed that an appropriate recrystallization treatment (703-753 K/1-5 min) could be used to acquire completely recrystallized grains with size <10 μm, contributing to better formability/ductility. The coarsening rate of these fine recrystallized grains is fairly low even though extending the solution treatment times at 753 K. Therefore, it indicates that the recrystallization dynamical equation would be a useful method to adjust recrystallization temperatures and times to satisfy various requirements of structures and properties.
Abstract: The development of aviation industry demands hot rolled aluminium alloy extra thick plates. However, it is quite difficult to obtain sufficient and uniform deformation of extra thick plate by conventional hot rolling process. The asymmetric hot rolling can generate an additional shear deformation and significantly improve the equivalent strain at the centre of the plate and consequently the uniformity of the microstructure, and mechanical properties. In the present work, the asymmetric rolling (ASR) was achieved by adjusting the diameters of the upper roll and the lower roll and was used to prepare hot rolled thick plate of an aluminium alloy. The effect of the asymmetric hot rolling process on the deformation, shape control, microstructure and mechanical properties was experimentally studied. The results showed that the ASR has a significant effect on metal deformation and can somehow refine microstructure and improve the uniformity of microstructure and properties although plate bending often happens during rolling process. This paper presents these results and gives corresponding discussions.