Numerical Simulation And Optimization Of Technological Parameters For Horizontal Continuous Casting Of Slab Metallic Glasses

Horizontal continuous casting?HCC?process of glassy alloy plate is very complicated,which still remains at the start-up stage so far with plenty of problems to be solved,especially lacking of general theories for interactions between glass transition process,complexity and elastic-plastic deformation of glassy alloys.In addition,it is also difficult to make real-time detections of process parameters.Trial-and-error or redundant methods are widely adopted currently to solve problems,but variation trend of the solidification front cannot be obtained herein.This paper,based on the self-developed HCC equipment,established the mathematical model of 3D temperature field in HCC process using finite element analysis software of ProCAST.The solidification process and heat transfer characteristics during HCC process were analyzed to determine impacts of approximate treatment of thermophysical parameters.Influences of parameters on solidification process is also analyzed and optimized by orthogonal and variable-controlling method.Glassy alloy forming ability was primarily characterized by Rc criterion,i.e.,the critical cooling rate.It's generally acknowledged that glassy alloys can be formed if the instantaneous cooling rate is higher than Rc.The results of calculation and experiment confirmed that criterion.Simulation results showed that the thermal conductivity could be calculated approximately among thermophysical parameters used in numerical simulation of the glassy alloy HCC,revealing negligible impacts of numerical value of the similar amorphous alloy on calculation results.The specific heat,by contrast,affects the results significantly.Thus,assumptions,boundary conditions and thermophysical parameters set in this investigation were reliable.Simulation analysis illustrated that it,when the pull-stop cycle mode was adopted,was reasonable to control the drawing speed,casting temperature and starting position of the casting within 2-4 mm/s,1000-1200?and 0-6 mm to the mold inlet,respectively,to meet critical conditions for glass formation.When the uniform speed drawing mode was employed,the drawing speed should not exceed 3 mm/s in order to meet critical conditions of glass formation.Furthermore,it was preferable to draw with 2 mm/s at uniform speed drawing mode than draw with 3 mm/s at pull-stop cycle mode.To summarize,factors influencing the shape of the solidification front followed the order of drawing speed>pouring temperature>starting position of drawing;factors influencing the equilibrium state of the solidification front as well as glassy contents in plate followed a different order of drawing speed>starting position of drawing>pouring temperature.The optimal combination of process parameters included casting speed of 4mm/s,casting temperature of 1080?,and starting position of casting located at the 14 mm position of the mold inlet.(Cu₄₇Zr₄₅Al₈)_98.5Y_1.5 plate with high glassy contents was successfully manufactured in experiments on the basis of numerical simulation results.