Research On Dragon Rolling And Heat Treatment Of7055Aluminum Alloy

Abstract:Dragon rolling is a new technique, which is achieved by an offset distance of upper roll in outlet direction on the basis of asynchronous rolling. In this paper, the OM、TEM and mechanical property of dragon rolling with two different speed ratio(1.1and1.3) were compared with the symmetrical rolling to research the difference between symmetrical rolling and dragon rolling. At the same time, the effect of solid solution treatment and cooling method of regression on7055aluminum thick plate were studied, the microstructure of the thick plate have been investigated by optical microscopy(OM), scanning electron microscope(SEM) and transmission electron microscopy(TEM) respectively. The main conclusion are as follows:(1) Dragon rolling has changed the strain state of the center layer of7055aluminum alloy rolling plate after80%total deformation degree, and then changed its texture configuration the center layer texture are formed a rotating cube texture ({001}<110>), and a typical rolling deformation textures(Cu texture ({112}<111>), B texture ({011}211>) and S texture ({123}<634>)) were weaker than conventional rolling. Dragon rolling fast roller side of7055aluminum alloy rolling plate texture for stronger for C texture, texture and S texture; And slow roll side in addition to the popular C texture, texture and S texture, also has a strong cube texture ({001}<110>).(2) Conventional symmetrical rolling led to small fraction of recrystallization, and the tensile strength was624MPa; The deformation energy storage after dragon rolling with speed ratio1.3is higher, so the plate recrystallization fraction after solid solution is larger, leading to lower tensile strength of only600MPa; The pate recrystallization fraction after dragon rolling with speed ratio1.1was moderate, but the tensile strength was highest, which was634MPa. This difference of the mechanical properties may be impacted by both the degree of recrystallization and texture of each layer.(3) Compared with the conventional two-stage solid solution, the plate recrystallization of each layer after slow multi-stage solid solution was significantly reduced, the mechanical property of each layer is greatly increased, the tensile strength an average increase of25MPa, interface average increase30N*mm-1, aKv average increase1J/cm2, The exfoliation corrosion resistance of multi-stage solid solution have greatly increased than the two-stage solution also.(4) Three different cooling rate of7055aluminum alloy pre-stretching plate regression in RRA were used:17.5℃/s (water quenching)、10℃/min(the natural air cooling) and3.5℃/min(fan blowing cold), the study found that the samples’cooling time of natural air cooling was too long, the precipitated phase were serious coarsened, so the strength and toughness of surface, subsurface layer and center of decreased a lot, its center fell, the most serious intensity down30MPa than water quenching, interface down90N*mm1; Compared with water quenching, mechanics performance of fan blowing cold samples degradation is lesser, both strength and interface within20, but the tensile strength of fell from center to the surface layer was only5.57%, but the sample of water quenching was7.11%. through fan cooling reduces the tensile strength of7055aluminum alloy thick plate but can effectively improve the mechanical properties thickness direction uniformity.