Study On Surface Modification Technology Of Aluminum Alloy Based On Ultrasonic

Nowadays,the oxide film of Al alloys become the key constraints to use this alloys more widely.Electroplating is often used in industry to modify Al alloys,but electroplating waste can cause environmental pollution.Ultrasonic propagation in liquid solder causes cavitation and acoustic effects,which can be used to smash the surface oxide film of Al alloy,promote wetting of the liquid solder on it and form the metallurgical bond.Sn-based solder is widely used in the electronics industry.However,the solubility of Sn-Al is very small and it can not form the metallurgical combination,which limit the application of the Al alloy in the field of the electronics industry.Baseed on this,ultrasound-assisted fluxless brazing of Al/Al joints with Sn-based filler metals was achieved in this study.The influence of the ultrasound process on Sn-Al bonding was studied,the microstructure and mechanical properties of the joint was also studied.At the same time,the Sn-based brazing filler metal was coated on the surface of the Al alloy by ultrasonic assisted brazing,and the most excellent plating process parameters were obtained.The results showed that all the three kinds of Sn-based solder could get the good quality of the Al alloy joints at the temperature of 300 ℃ and the ultrasonic time of 10 s.The microstructure of pure Sn solder brazing joint was α-Al and β-Sn,and the maximum shear strength of joint was 38 MPa.What’s more,the fracture position of joint was the interface,and the fracture way was the ductile fracture mode.Sn-9Zn solder joint was composed of Sn-9Zn eutectic,α-Al and rod-like Zn-rich phase.The maximum shear strength of the joint was 61 MPa,and the fracture position was in the weld,and the fracture way was the ductile fracture mode.The microstructure of Sn-3Ag solder brazing joint was Sn-3Ag eutectic,α-Al and Ag2 Al.Its highest joint strength was 48 MPa,and the fracture position was in the weld,and the fracture way was the intergranular fracture mode.Increasing the temperature and the ultrasonic action time will increase the Al content in the weld and improve the bonding effect.The Al content in the weld was 10.03% at 400 ℃.The addition of Zn can promote the wetting and spreading of Sn on the Al surface,promote the dissolution of Sn into the matrix,and enhance the interfacial bonding of Sn-Al.The Al substrate surface can be coated with pure Sn in order to achieve the surface modification of Al substrate,at the temperature of 300 ℃ and the ultrasonic interval of 12 s.The hot-air leveling process resulted in a flattened Sn layer and a smooth transition of the antenna solder joints.Sn-9Zn layer was coated on the Al substrate surface successfully at the temperature of 300 ℃ and the ultrasounic time of 10 s.Using high-power ultrasonic welding machine,a comprehensive modification of large area Al substrate can be achieved.What else,increasing the ultrasonic power and enhancing the ultrasonic action time can increase the surface plating effect.At last,no cracks and holes were found in the Al substrate interface coated with pure Sn,during Al/Cu reflow soldering process.