Microstructure evolution and mechanical properties of spray-formed 7055 Al alloy subjected to cryogenic rolling

Cryogenic rolling impacts on microstructure and mechanical properties of spray-formed 7055 (SF-7055) Al alloy were investigated. Results show that with the increase of the reduction from 20% to 80%, the grain of cryogenic rolled SF-7055 Al alloy is elongated to form a fiber texture. Numerous proliferating dislocations in the microstructure accumulate into dislocation walls and cells, and eventually form subgrains. These subgrain boundaries divide the original grain, thereby reducing the grain size. Under severe deformation conditions, they even enable the formation of nanograins. Meanwhile, the Cu-rich precipitates in the matrix are also broken and refined under the action of large rolling stress. In the process of cryogenic rolling, the tensile strength and hardness of SF-7055 Al alloy gradually increase, while the plasticity decreases. Moreover, the fracture morphology of cryogenic rolled SF-7055 Al alloy gradually transforms to the ductile and quasi-cleavage hybrid fracture characteristics with increased reduction.