Study On Simulation Of Liquid Die Forging Process Of Aluminum Alloy And Its Performance

With lightweight conception proposed recently,liquid die forging has been used as an advanced forming process.The liquid or semi-solid metal is filled into the mold cavity at a relatively low speed,and solidified with sufficient pressure and deform slightly plastically.Finally,internal defects such as stoma,shrinkage cavity and loose in the castings were reduced or eliminated.As a result,casting production with fine grain,uniform organization,complex shape and excellent performance were obtained.However,the current production technology is inexperienced.Nowadays,mold design and process parameters are mainly determined via conducting mode-test,which not only increase the production duration,reduce production efficiency,waste resources,increase costs but also result in productions with inferior performance.Thus,in the present study,simulations of liquid forging filling and solidification process were performed using Anycasting to optimize the mold structure and process parameters.The main research contents and conclusions are as follows:(1)Numerous defects were detected when filling and solidification process were simulated according to the initial scheme.For instance,shrinkage and porosity were observed in the bonding parts of the castings;air-roll occurred easily during filling process;gas involving was easily formed outside the rim,resulting in oxide inclusion;the producing efficiency would be reduced due to the low cooling rate induced by the handle with a large volume.(2)The structure of the initial mold was optimized based on the numerical results.Particularly,the flow channels were added to reduce the risk of shrinkage;exhaust slots were added and the size of the slag bag was raised to improve gas involving;the temperature distribution inside the mold was increased by increasing the local cooling device and replacing core material,thereby achieving sequential cooling of castings;the time of the handle's solidification was reduced by adding cooling water.As a consequence,the producing efficiency was raised.(3)Orthogonal test was conducted to investigate the influence of the process parameters(pouring temperature,filling rate,preheating temperature of the mold and packing pressure)on the quality of the castings.Here,shrinkage area was used to assess the quality of the obtained castings.By range analysis,it was found that the descending order of the parameters was pouring temperature,preheating temperature,packing pressure and filling rate.And the optimized parameters were determined as pouring temperature 670?,filling rate 0.1 m/s,mold preheating temperature 180?,holding pressure 75 MPa via numerical results.(4)The simulation was performed again in this section.It was found that shrinkage,gas involving,high pressure and low cooling rate of the handle were improved.Castings were produced using the optimized mold and process parameters.Meanwhile,non-destructive inspection was conducted on the section of the produced castings.The results showed that the shrinkage defects and the gas involving inside the castings were improved significantly using the new scheme.82 percent of the castings met the national standard,and the numerical results were confirmed.(5)By comparing the performance of metal casting and liquid die forging,it is found that the performance of AlSi9Mg aluminum alloy wheel produced by liquid die forging process outperformed that of metal castings.The heat treatment process of AlSi9Mg aluminum alloy was 535? × 5h+160? ×4h,and the average performance of castings under this process can reach Rm=298MPa,RP=231MPa,A=3.32%,HBW=117.5.