Sic_p/6061al Composite Fabricated By Liquid Phase Mechanical Stirring Casting

SiC particulate reinforced 6061 aluminum matrix(SiC_p/Al) composite having a high application potentiality in the fields of automobile,electronic,military and aviation industries,is regarded as one of the most important materials of the 21st century because of its high specific strength and stiffness,excellent wear resisting property,dimensional stability,low thermal expansion coefficient and low processing cost.Liquid phase mechanical stirring casting has the most promising manufacture method, by which aluminum matrix(SiC_p/Al) composite having good mechanical and physical properties can be prepared.Moreove,its equipments and technological operation are simple and the cost is lower compared with some other main processing methods,such as powder metallurgy,spray deposition,pressure infiltration,stirring casting,ect..Therefore, studies on the process of liquid phase mechanical stirring casting would make sense to composites' popularization and application.In this paper,SiC_p/6061Al composite was fabricated by liquid phase mechanical stirring casting with the protection of Ar.The effects of stirring process parameters,adding alloys,auxiliary stirring equipments and pretreatments of SiC particles on the distribution of SiC_p and interface reaction between SiC_p and Al,were investigated systematically by using optical microscopy(OM),scanning electron microscopy(SEM) with spectrum analysis(EDS),X-ray diffraction(XRD).The origins of casting defect were analyzed,and the mechanical properties of composite were also tested.The results show that when the Ar flow-rate is 0.4 m~3/h,stirring temperature is 740℃, stirring speed is 1200 r/min and with short stewing time after stirring,SiC particles tend to an uniform distribution with slight interface reaction and few casting defect.With the content of Mg or Si in matrix alloy increasing,interface reaction between SiC particles and Al is limited effectively,but leading to a disadvantageous increase in aggregating of SiC_p and porosity.Using eight-layer propellers with screw thread and adding spiral steel ring as auxiliary stirring equipments,the distribution of SiC particles is uniform relatively,and conglobation,partial aggregation,chain and annular distributions of SiC particles reduce, as well as casting defect.When SiC particles are coated with Ni-P on their surface,and heat-treated in low temperature in vacuum,the wetting property between SiC particles and Al becomes better. This would lead to a more uniform distribution of SiC particles and limit the interface reaction between SiC_p and Al.With the improvement of uniformity distribution of SiC particles and mitigation of interface reaction,mechanical properties of composites were enhanced evidently,and 218MPa of tensile strength was obtained,reinforcement effectiveness of SiC particles is also marked.