Interface Structure And Properties Of Cu/Al Prepared By Ultrasonic Additive Manufacturing Assisted Pulse Current

As a new manufacturing method,ultrasonic consolidation technology has attracted more and more attention and research in recent years.Although the current ultrasonic transducer technology can achieve the maximum output power of 9-10k W,it still can not achieve the ideal effect for some high strength metal to metal consolidation of the same and different species.Therefore,in order to achieve the purpose of rapid prototyping manufacturing and increase the selection range of ultrasonic consolidation technology in materials,this paper will use the joint manufacturing of ultrasonic wave and pulse current to carry out the experimental research on ultrasonic consolidation of Cu/Al Laminated Composite under the condition that it is difficult to obtain better interface bonding by traditional forming process The interface and bonding properties of the samples were characterized and analyzed by means of linear welding density measurement,microhardness,scanning electron microscope observation and peeling test.The role of pulse current in the process of interface consolidation was analyzed by EBSD and TEM,so as to obtain the action law and interface bonding mechanism of pulse current in ultrasonic consolidation process.At the same time,the effects of pulse current parameters and cumulative consolidation on the interfacial bonding properties of Cu/Al layered composites were studied.In the experiment,the double-layer structure was used to prepare the composite material,which was Al6061(base plate)-Al/Cu-Al/Cu-,based on this structure,the prepared Cu/Al layered composite material included the Al/Cu interface not affected by the indenter and the Cu/Al interface affected by the compressive head.The optimal consolidation parameters of Cu/Al laminated composites were determined by experiments:normal pressure is 175 kgf,amplitude is 30?m,consolidation speed is 20 mm/s,consolidation temperature is 170?.At the same time,the technological range of voltage and frequency of pulse current in the process of auxiliary consolidation is determined:voltage range from50 V to 100 V,frequency range from 100 Hz to 300 Hz.The results show that the low density and high density pulse current can reduce the average value of consolidation defects from 6.4%to 5.5%and 3.1%respectively.The addition of pulse current can effectively reduce the interface line welding defect density.In addition,the energy consumption in the process of ultrasonic consolidation is reduced by adding pulse current.XRD results show that there is no obvious intermetallic phase in the process.Hardness test shows that high density pulse current assisted ultrasonic consolidation has work hardening effect on Cu.The results of peel test show that the maximum peel force of Al/Cu interface increases from 76.3N to 118.9N,and the consolidation effect is obviously improved.It is found that there are many tearing edges on the fracture surface and the fracture surface is quasi cleavage fracture.EBSD results show that the dislocation density of Cu/Al interface increases and that of Al/Cu interface decreases during ultrasonic solidification assisted by pulse current.At the same time,the grain volume fraction of Cu/Al interface changes little before and after the addition of pulse current;however,it is obvious that the volume fraction of recrystallized grains on the side of Cu and Al increases greatly after the addition of pulse current,while the volume fraction of deformed grains decreases greatly,and a layer of fine sub grains can also be seen at the interface;The results of texture analysis show that the original Cu belt cubic texture rotates under the action of strong energy of pulse current to generate copper texture and R texture.The{211}<011>texture of the original al band is transformed into cubic texture under the action of pulse current.Under the action of pulse current,the r-texture of the far interface al band region without abnormal grain growth transforms into cubic texture and rotational cubic texture,while in the IZ region,the texture type is similar to that of the upper and lower Cu band and Al band.TEM results show that the elements at the Cu/Al interface and Al/Cu interface are not diffused,but the oxides at the interface are broken and dispersed in different degrees.The oxide dispersion at the Al/Cu interface is larger than that at the Cu/Al interface,and the metallurgical bonding at the interface is stronger than that at the Cu/Al interface during the consolidation process,which is consistent with the peel test results Accordingly,the mechanism of surface oxide removal by ultrasonic consolidation is further proved.However,after the introduction of pulse current,there is obvious element diffusion at the Cu/Al interface and Al/Cu interface.At the same time,the Al/Cu interface recrystallizes under the action of pulse current,forming a fine-grained layer of Cu,which further enhances the interface bonding.It can be seen that pulse current can enhance the interface bonding of Cu-Al layered composites by promoting atomic diffusion and grain growth.The results of single factor test show that the maximum peeling load decreases with the increase of voltage range from 50 V to 100 V and frequency range from 150 Hz to 300 Hz,and then increases with the increase of voltage.With the increase of frequency,the maximum peel load increases and then decreases.By using the surface optimization method,the equation model between the pulse current voltage and frequency and the maximum peeling load at the interface of Cu Al layered material is obtained:y=137.64-4.22₁+18.45₂+22.79₁²-32.89₂²(₁-voltage,₂-frequency).The reliability of the modified model is verified by experiments.At the same time,the optimized process parameters of pulse current assisted ultrasonic consolidation of Cu/Al Laminated composite were obtained:voltage 50 V,frequency 240 Hz.In addition,through the double factor interaction analysis and significance analysis,it can be seen that the impact of pulse current and voltage on the interface bonding quality is more significant.The cumulative consolidation test shows that ultrasonic has little effect on the interface cumulative consolidation of Cu/Al layered composites,while pulse current cumulative consolidation can enhance the interface bonding.