Research On Microstructure And Mechanical Properties Control Of Variable-cavity Liquid Forging ZL205A Alloy

ZL205A alloy is widely used in various fields of industrial production because of its excellent mechanical properties.However,its crystallization range is as high as about 100?C,which is easy to bring hot crack,shrinkage cavity,porosity and porosity during solidification and crystallization,which greatly limits its application space.The casting defects can be eliminated to a great extent by improving the undercooling degree and modification strengthening,which provides ideas for practical production.After the conventional liquid forging process,only a small amount of plastic deformation occurs,which can not meet the actual production requirements.In order to further improve the properties of ZL205 A alloy billet after composition modification,the liquid die forging process of deformation chamber was adopted.The alloy solidified and crystallized under pressure,and applied more pressure to produce large plastic deformation after a period of time,which can shape the workpiece and improve the properties.In order to exhaust and eliminate defects,the alloy blank preparation die is designed and manufactured.Based on the principle of large plastic defo rmation,the liquid die forging forming die with deformation cavity is designed and manufactured.The melting process window of ZL205 A alloy is determined,and the ZL205 A alloy and the deformed cavity parts were prepared by the integrated process of melting material,modification,impurity removal,heat preservation,pouring and pressure maintaining.The effect of Zr and Sc on the microstructure of ZL205 A Alloy was studied by OM and SEM.After adding a certain amount of Zr element on the basis of SC element in ZL205 A aluminum alloy,the microstructure and properties of Al 3(Sc,Zr)composite particles formed during solidification and crystallization of billet are better than al3 sc particles.Proper amount of Zr and Sc elements can refine the grain,optimize the structure and improve the comprehensive mechanical properties of the alloy.However,excessive Zr and Sc elements will make Al 3(Sc,Zr)particles aggregate,which will reduce the comprehensive mechanical properties of aluminum alloy.It is found that the comprehensive mechanical properties of ZL205 A Alloy Containing 0.4% Sc and 0.15% Zr are the best.The elongation reaches 15.7% at room temperature,the tensile strength can reach 398.5MPa,the elongation reaches 24.1% at 150?C,the tensile strength reaches 217.8MPa,and the elongation at 150?C after T5 heat treatment slightly decreases to 15.8%,and the tensile strength increases to 345.1MPa.The principle and process of the liquid forging of the deformation cavity are expounded.The filling and deformation process of the liquid forging of the deformation cavity is simulated by Pro CAST and DEFORM-3D numerical software.The die and process parameters are designed by the numerical simulation results.When the aluminum liquid is poured at 750?C,the mold is preheated at 250?C,and the pouring time is 7s,the aluminum liquid is filled in the mold stably and flows in layers,which will not cause problems such as scouring and inclusion.When the secondary pressure temperature increases,the denaturation ability increases and the load increases;when the loading speed increases,the plasticity ability increases and the load decreases;when the lateral pressure is applied to the workpiece,the punch load increases by 80%,the stress-strain also increases by about 50%,the workpiece maintains the three-dimensional compression stress state,and the grain is also obviously refined.