Effect of Al_3Sc precipitate on the microstructural evolution during accumulative roll bonding in Al-0.2 wt. percent Sc alloy

摘要

The cold-rolled Al-0.2wt. percent Sc alloy sheets were conducted the following two preliminary heat treatments: (1) as solution treatment at630 deg C for 1 h, and (2) as artificial aging at 300 deg C for 5 h. The accumulative roll bonding (ARB) was followed up to eight cycles at ambient temperature. The stored energy release caused by annihilation of dislocation and recrystallization in aged alloy was higher than that in solution treated one in the 2-cycle sample, and this aspect was reversed with increasing cycles. The fraction of high-angle grain boundaries (HAGBs) in both alloys was increased gradually with increasing equivalent strain. However, the alloy of aged and ARBed had relatively higher fraction of HAGBs than the alloy of solution treated and ARBed at the same strain level. The former formed lamellar structure faster1 than the latter. This variation can attribute to the fact that the nanosized and semi-coherent Al_3Sc precipitates hinder the migration of boundaries and dislocations. However, those precipitates cannot generate the sufficient pinning effect because the driving pressure for recrystallization surpasses the Zener pinning pressure.