The Influences Of Melt-treatment On The Flow Stress At High Temperature And Microstructure Of Aluminum Sheet Used For Easy-open-can

The relationship between the metallurgical quality of aluminum sheet used for easy-open-can and its deformation behavior at high temperature is systematically studied with aids of dynamic thermal/mechanical simulation technology, OM and TEM analysis methods. Otherwise, primary multi-path hot compression simulation is carried out to study the influence of hot deformation technics on pratical hot rolling. The main conclusions are as follows:① The metallurgical quality and the mechanical properties (especially plasticity) of aluminum sheet used for easy-open-can can be improved remarkably by adopting high-efficient melt-treatment and proper homogenization process (450℃×12h). The flow-stress curves at high temperature of the materials treated by various processes are different under different deformation conditions. At low temperature or high strain rate, the difference is great. With the increase of temperature or the decrease of strain rate, the dynamic softening is more obvious, and the flow stresses descend, and the difference of flow stresses among the materials treated by different processes becomes smaller and smaller. At high temperature or low strain rate, the difference is tiny. The function between stable flow stress and strain rate, temperature can be expressed more suitably by the Arrhenius relationship modified by hyperbolic sine function, which means that the hot compression deformation is controlled by thermal-activation. On the base of the result, the hot deformation material constants are computed. The thermally-activated energy Q value gets smaller with the elevation of the effect of melt-treatment, and proper homogenization (450℃×12h) also makes Q value decline, so the best deformation ability at high temperature is obtained. Besides, the influence of melt-treatment on Q value is greater than that of deformation conditions.② The influences of melt-treatment and deformation conditions on microstructures of this material during hot deformation are both remarkable. The recrystallization grains becomes smaller and more well-proportioned if the effect of melt-treatment is better, moreover, proper homogenization condition makes the distribution of grains more symmetrical. With the increase of temperature, the density of dislocation decreases, and the recrystallization grains are coarser. With the increase of strain rate, the density of dislocation increases obviously, the grains are elongated and the uniformity of microstructure gets worse.③ Melt-treatment has great influence on dynamic softening in the course of hot deformation. The reduction of metallurgical defects, such as inclusions and the thick second phases, restrains the progression of dynamic recrystallization to a certain extent. But small original grains provide advantageous conditions for the forming of dynamic recrystallization nuclear cores, so tiny and symmetrical microstructure can be obtained after hot deformation. And the small second phases separated out after homogenization will restrain the growth of recrystallization grains in the course of hot deformation. During the start and transition periods of hot deformation, subgrains are formed by repolygolization, and the dynamic recrystallization nucleation cores are formed by the congregation and growth of subgrains. Furthermore, the cores can also be formed by the way of the bow of grain boundry.④ The result of the primary multi-path hot compression simulation shows that for the aluminum sheet processed by high-efficient melt-treatment and homogenization (450℃×12h), under the suitable deformation that is at 400℃, 3 pathes, and 1.0~3.0min interval time, ideal deformation microstructure can be obtained when strain rate is equal to 0.1s-1, compression rate 50%.