Study On Brazing And Friction Stir Welding Of High Silicon Aluminum Alloy

High silicon aluminum alloy with a low density,high thermal conductivity,good wear resistance and so on,which has a wide range of application in the automotive,military,electronics industry materials,etc.The Si content of the high silicon aluminum alloy is high,and the structure of the primary Si and the eutectic Si is relatively coarse without degeneration,resulting in a low mechanical property and difficult to satisfy the requirement of the structural member.With the continuous optimization of alloy composition and the development of preparation technology,the comprehensive performance of high silicon aluminum alloy has been significantly improved,in the aerospace aircraft electronic systems,satellite base stations,mobile communications systems and transportation and other fields are also increasingly high Silicon aluminum alloy structural parts.Therefore,the attendant high silicon aluminum alloy connection technology has become an urgent problem to be solved.In this paper,Zn-5Al brazing filler metal was added to the surface of high silica aluminum alloy by hot-dip plating,and then brazed in the furnace.The influence of connection temperature and holding time on the microstructure and properties of the joint was studied.The results show that the brazing method of hot-dip Zn-5Al brazing filler metal to the surface of the base metal can complete the connection between the base metal and the brazing filler metal,and realize the flux-free connection of the high silicon aluminum alloy.In the holding time of 10 s,with the increase of the connection temperature,the mechanical properties of the joints with good mechanical properties were obtained when the connection temperature reached 395?,the shear strength was 66 MPa,the fracture was tough and the temperature was increased and the joint strength decreased.At the temperature of 395 ?,the AlSi14 high silicon aluminum alloy brazing was carried out by using Zn-5Al brazing filler metal.With the increase of the holding time,the Al content in the weld increased,and the transition layer of the B-side transition layer was close to the high silicon aluminum substrate.For the 25 s,the Si phase,which is uniformly dispersed in the central region of the brazing seam,has an effective pinning effect on the joint structure,which was helpful to improve the joint performance.The joint shear strength reached 119 MPa.AlSi14 high silica aluminum alloy was subjected to welding test by friction stir welding.The results show that the friction stir welding of AlSi14 high silica aluminum alloy can be achieved by using different welding parameters.The weld nugget zone is very small due to the dynamic recrystallization;thermo-mechanically affected zone is close to the weld nugget zone and the elongated tissue appears at higher speeds;the grain size of the ? and the eutectic Si grains in the heat affected zone increases with respect to the base metal.When the rotational speed of the stirrer is 1300 r / min and the welding speed is 100 mm / min,the tensile strength of the joint can reach 92%;the fracture occurs in the front heat affected zone,and the fracture is a mixture mode of brittle fracture and ductile;the micro-hardness of the joint is approximately "saddle" shape distribution,the hardness of the base metal is high,and the hardness is low near the heat affected zone.