Microstructure evolution and strengthening mechanisms of spray-formed 5A12 Al alloy processed by high reduction rolling

The extrusion preform of the spray-formed 5A12 Al alloy was hot rolled using high reduction rolling technology. By means of transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS), the microstructure evolution was studied and the strengthening and toughening mechanism was thereby proposed. The results indicate that discontinuous and continuous dynamic recrystallization occurred during the hot rolling deformation of the spray-formed 5A12 Al alloy. The grain size was significantly refined and the micro-scale grains formed. Partial dynamic recrystallization leads to a significant increase of dislocation density and cellular structure. The Mg atoms were distributed in the Al matrix mainly in the presence of solid solution rather than the formation of precipitate. High solid solution of Mg atoms not only hindered the dislocation motion and increased the density of dislocation, but also exhibited a remarkable solid solution strengthening effect, which contributes to the high strength and high toughness of the as-rolled sheets. The tensile strength and elongation of spray formed 5A12 Al alloy at room temperature after 3 passes hot rolling were 622 MPa and 20%, respectively.