Research On The Preparation Of High Silicon Aluminum Alloys Based On Friction Stir Processing Technology

High-silicon aluminum alloy has been widely used in many industrial domains such as automobile,aircraft,tank and marine engine due to its small specific gravity,good thermal conductivity,good corrosion resistance,high strength and hardness,and easy recycling.However,the preparation methods of high-silicon aluminum alloy have their advantages and disadvantages,which limited its preparation and usage.Therefore,the research area of preparing high-silicon aluminum alloy is to choose an appropriate preparation technics,in order to obtain fine silicon particles distributed uniformly with less edges.Friction stir processing(FSP)could enable the densification,homogenization and refinement of the microstructure by severe plastic deformation,mixing,crushing and thermal exposure of the material in the processing area through the stir tool.On the one hand,friction stir processing can be used to prepare aluminum-silicon alloy.On the other hand,it can also be used to eliminate defects of casting aluminum-silicon alloy.In this paper,based on the study of the properties and the common used preparation methods of high silicon aluminum alloys,adding silicon powder by friction stir processing and casting combine with friction stir processing were used to prepare high silicon aluminum alloy through the self-designed stir tool and fixture.The results showed that both the adding silicon powder by friction stir processing and casting combine with friction stir processing could be used to prepare the high-silicon aluminum alloy with uniform distribution of silicon particles and there were no defects in the material by cone threaded tool.The optimal process parameters are 950 rpm,47.5 mm/min,stirring 4-pass with changing the stirring direction alternately.However,the content of silicon in the Al-Si alloy which was prepared by the adding silicon powder by friction stir processing method can only reach 14.2% and it could not meet the experimental qualification.The microstructure and properties of Al-40 Si materials,which was prepared by the casting combine with friction stir processing method were analyzed.The silicon particles were significantly refined after the casting combine with friction stir processing method,and the average diameter of silicon particles was about 3 ?m.Both the micro-hardness value and the macroscopic hardness value were increased from 70 HV of the base metal to about 120 HV,raised about 60%.In the mean time,the tensile strength was increased from about 50 MPa of the base metal to about 270 MPa,which was almost 5 times than that of the base metal.During the tribological test,the amount of abrasion of friction stir processed material remain stable with the increase of loading force,and the wear properties has been improved significantly.