Semi-solid Billets Preparation And Its Deforming Numerical Simulation Of 6xxx Aluminum Alloy

Semi-solid Metal Forming (SSM) is a new process because of its low consuming energy, high forming precision and high properties, which is considered as the most potential one of metal forming in the 21st century. In this paper Liquidus Semi-continuous Casting (LSC) was presented to produce the semi-solid billets of 6063 and 6061 aluminum alloys. LSC is a process that obtains the fine, uniform rosette-shaped or net-globular grains microstructures which are suitable for SSM, the process is simple and the producing efficiency is high.The grain size and roundness extent of the as-cast microstructures were analyzed with the Image-Pro Plus. The grain size and roundness in the center of billets were smaller than the edge. With the increase of the casting velocity, they became large. It gained good non-dendritic microstructures that LSC was performed at a little high liquidus temperature and low casting velocity. The mechanics of the nucleation near liquidus LSC and the growth mechanics of the formed grain were analyzed.A furnace was used to investigate the reheating microstructures of the 6063 and 6061 alloys cast by LSC at the different temperature and the different isothermal holding time. It was analyzed that liquid fraction, effective liquid fraction, grain average diameter and round extent of the reheated microstructures with the Image-Pro Plus, gained the results of the reheated microstructures evolvement rule. The reheating experiments showed that after holding 20min at 615℃or 10min at 635℃,6063 aluminum alloy and after holding 10min at 620℃,6061 aluminum alloy could be reheated into semi-solid state with microstructure which was suitable for SSM.Visco-plasticity finite element analysis technology and the deformation mechanics of the semi-solid state were utilized in this paper. It was simulated that 6061 aluminum alloy extrusion at 620℃by the finite element software Deform-3D. The influences of extrusion velocity, die structure and die temperature on the punch force and temperature field, effective strain field, effective stress field of forward extrusion bars at the semi-solid state were investigated. Comparing with the results of extrusion simulation at 450℃. The different deformation mechanics worked the simulated results differences of solid and semi-solid state extrusion. It is that 3mm/s extrusion velocity,200℃die temperature,600℃extrusion tools temperature is reasonable semi-solid state extrusion process of 6061 aluminum billets at 620℃.