Research On Interface Heat Transfer Coefficient And Fluidity Based On Amorphous Alloy Casting

In recent years,amorphous alloys have a short-range order on a microscopic scale and a unique structure,which makes them have excellent mechanical properties and good mechanical properties.In addition,many amorphous alloy materials do not have a complete grain structure,so that they have excellent magnetic properties and good corrosion resistance.It is expected to become a material with broad application prospects in many fields such as biology,medical,aerospace,electronic technology,etc.However,if you choose to use the casting process to form an amorphous alloy,in order to obtain an amorphous alloy casting with a clear outline and a good shape,the alloy liquid is usually required to be cooled slowly,but,in order to obtain a completely amorphous structure,the alloy melt must also achieve a relatively large cooling rate,which is a long-standing contradiction in the process of forming an amorphous alloy using a casting process.Based on this,this article uses a combination of theoretical analysis and numerical simulation to study the effect of viscosity parameters on the wetting process,attempts were made to increase the surface texture of the mold to improve the fluidity,and changes in the casting process parameters to improve the casting ability of the higher viscosity amorphous alloy.The suitable process conditions for the Zr-based amorphous mirror forming process were initially given.Through the analysis of the related thermophysical parameters of ZL104 and Al87Ni10Pr3 and Zr41Ti14Cu12.5Ni10Be22.5 three different alloys,the relationship between viscosity and surface tension and the wetting characteristics of the molten metal on the mold were established.Through molecular dynamics theory and state The relationship between the wetting angle and the surface tension,(?),can be deduced by combining equations.When the base material of the mold is the same,the wetting angle between the melt and the mold is mainly determined by the surface tension of the melt.At the same temperature,the surface tension and wetting angle of the melt are related to the viscosity.The greater the viscosity,the greater the surface tension and wetting angle.Use Fluent simulation software to simulate the wetting process of the molten metal flowing through the micro-grooves on the surface of the mold.Due to the limitation of the viscosity of the molten metal,when the molten metal flows on the surface with the groove,when the groove is deep enough,the micro-groove cannot be completely wetted.As the viscosity of the molten metal increases and the temperature decreases,the length of the molten metal flowing into the groove gradually becomes shorter,and the greater the viscosity and surface tension of the molten metal,the less the effect of the molten metal wetting groove on the groove width changes.The influence of different micro-groove structure parameters on the flow state of the liquid metal was studied,and it was found that the temperature,viscosity,filling speed,groove width,groove shape and other parameters will affect the wetting process of the liquid metal.Due to the difference in the viscosity characteristics of the liquid metal and the process parameters,the slight difference of the gas gap layer at the bottom of the groove will have a great influence on the interface heat transfer between the liquid metal and the mold.The lower the filling rate of the liquid metal to the groove,the larger the width of the gas gap layer,resulting in a smaller interface heat transfer coefficient,and the better the flow capacity of the liquid metal in the mold.Adding micro-grooves on the surface of the mold will improve the fluidity by affecting heat transfer.The increase in the surface density of the groove will also increase the fluidity of the molten metal,and the greater the viscosity of the molten metal,the smaller the influence of the groove surface density on the fluidity of the molten metal..In addition,the improvement of process factors such as the increase in filling speed,the increase in pouring temperature and the increase in mold preheat temperature will have a positive effect on the fluidity of the molten metal,and under different process conditions,the fluidity of small viscosity alloys is significantly better than that of high viscosity amorphous alloys.The anti-gravity casting process of the amorphous mirror was numerically simulated,the influence of different casting schemes and mold cooling methods on the casting process was analyzed,and the original process parameters were optimized.The optimized process parameters are: groove density 1/2,mold preheating temperature 600?,filling speed 300mm/s,and forced w ater cooling during solidification.U nder this process condition,the liquid metal flow is relatively stable during the filling process,the liquid surface sloshing is small,the temperature field and flow field distribution in the casting are more reasonable,and the instantaneous cooling rate at the amorphous transition temperature is 15°C/s,which better achieves the shaping process of the amorphous mirror.