LSPWES Cellular Automata Simulation Method In Semi-solid Microstructure Evolution

Low superheat pouring weak electromagnetic stirring(LSPWES) techniqueis a new kind of semi-solid slurry preparation technology and it has arousedpeople’s attention for its advantages of simple process, high productionefficiency and so on. Although researchers have carried out a lot of work on thistechnology, the simulation of microstructure evolution during the process hasnot been reported by the current.A macro-micro coupled model which combines finite element and cellularautomaton is established according to the characteristics of LSPWES method inthe paper. ANSYS software is used to calculate the macroscopic electromagneticfield and flow field, microstructure evolution is simulated by using the CAFEmodule of PROCAST software and self-complied programs. The microstructureevolution under different parameters is simulated and compared with theexperimental results to test the accuracy of the simulation results. The mainresults are as follows:(1)The change of primary grain morphology of A356aluminum alloy inLSPWES method is closely related to the process parameters and it need mutualcoordination between each parameter to obtain high quality semi-solid slurriesby using this method.(2)At the condition of electromagnetic stirring, when the power supplyfrequency is decreased from50Hz to30HZ and then to10Hz, the magneticintensity and magnetic force increase, the primary-Al grains in the slurry ofthe semi-solid A356aluminum alloy are finer and the spherical extent is better.The raising of electromagnetic stirring power can increase the magnetic intensityand magnetic force gradually, it is conducive to the formation of the semi-solidA356aluminum alloy slurry with globular microstructure, but after the stirringpower increasing to a certain value, the optimization effect of keeping increasingthe stirring power to the shape and size of globular grains is not much thatobvious.(3)As the extension of mixing time, the morphology of primary α-Al gradually transforms from rosiness to a ball, we can obtain ideal globularprimary α-Al grains by stirring6s, if increasing the mixing time to8s, the effectis not obvious. With the reduction of pouring temperature, primary-Al changesfrom rosette-like grains to spherical grains, the size is smaller and distribution ismore evenly.(4)The best conditions for LSPWES method to prepare semi-solid A356aluminum alloy slurry are as follows: the power supply frequency is10Hz, thestirring power is1.2kw, the stirring time is6s and the pouring temperature is630℃. Under optimal parameters, the primary grains are fine globularity andthey will preserve original shape until they contact with each other and thengrow up to be slightly larger crystals or rosiness crystal balls during thesubsequent growth process.