Effect of initial structure on grain refinement to submicron size in Al-Mg-Li alloy processed by severe plastic deformation

The influences of grain structure and precipitates on the formation of submicrocrystalline (SMC) state in 1420 alloy subjected to thermomechanical treatment including severe plastic deformation at room temperature were investigated. It was established that the deformed alloy (e=3.8) has a fragmented structure and a fragment size does not depend on both the initial grain structure and the presence and the size of precipitates. Subsequent annealing at 250 degrees C for 0.5h results in complete transformation of the fragmented structure to a grained one. Its formation occurs by the mechanism of primary continuous recrystallization. In the quenched alloy with single modal distribution of precipitates by size the initial grain structure does not almost affect the size of recrystallized grains. The formation of bimodal precipitate structure before the deformation results in obtaining of coarser grains. The revealed features of SMC structure formation are analysed in terms of their physical nature.