Optimization Of The Semi-solid Formation Technology For Al-Si-Fe Alloy

Aluminum alloy with high Si content has high wear resistance and low thermal expansion properties,which is the very potential structure and function integration material. However,silicon phase coarse problem can not be solved by the conventional preparation process,so that the mechanical properties of the alloy are very low,and its application has been seriously hampered.Semi-solid formation process can refine the first precipitates phase by electromagnetic force stirring the alloy melt,and increases the mechanical performance of the alloy.Furthermore,the Semi-solid formation technical cost far lower than spray deposition rapid solidification technology.Therefore,Al-20Si-5Fe-3Mn-4Cu-1Mg alloy is studied in this paper and every stages of semi-solid forming process has been simulated and tested.The influence of the semi-solid forming to the alloy microstructure has been analyzed,then the main factors of the second phase crushing and fining has been explored.Semi-solid extruding formation process of Al-20Si-5Fe-3Mn-4Cu-1Mg alloy has been simulated by DEFORM-3D.The influence of blank shape,deformation temperature, friction and extrusion ratio to the equivalent strain,equivalent stress and extrusion force has been analyzed.Simulation results show that Al-20Si-5Fe-3Mn-4Cu-1Mg alloy has good plastic,deformation uniform,the most favorable crushed when the heating temperature is 580℃,soaking time is 40min,and the friction factor is 0.2.As a basis for comparison,the semi-solid forming process and die system has been optimized.The experimental results indicate that the laminated structure eutectic Si phase of Al-20Si-5Fe-3Mn-4Cu-1Mg alloy is broke,size decreased,and the distribution became more uniform after the electromagnetic stirring.The microstructure of Al-20Si-5Fe-3Mn-4Cu-1Mg alloy is changed obviously after semi-solid formation.Coarse tabular and needle-like primary phases are replaced by round grainy phases,whose grain size is reduced largely.Eutectic Si phase also becomes finer and more even.The higher the extrusion ratio is,the more obvious the effectiveness of refining and breaking,and the more uniform of distributing.At the same time,the experience results prove that the simulated results are very reasonable.Semi-solid formation can improve the mechanical property of Al-20Si-5Fe-3Mn-4Cu-1Mg alloy.The maximum tensile strength is 251MPa,increased 128.2%comparing with as cast condition,the elongation percentage could reach 1.4%,increased 180% comparing with as cast condition.