Research On Ultrasonic Preparation Process And Interface Bonding Mechanism Of Diamond/Copper Composites

Diamond/copper composites with high thermal conductivity can achieve complementary and synergistic performance among components,and have excellent comprehensive performance,playing a crucial role in important fields such as national defense,aerospace,and electronic information.In response to the current dependence of diamond/copper composites on high-temperature and high-pressure processing conditions and green environmental protection issues during the manufacturing process,this paper proposes an ultrasonic preparation method for diamond/copper composites.This method achieves the stable existence of diamond reinforced phase particles in laminated composites through surface metallization treatment and spatial position constraints,and the free forming and processing preparation of the composites using ultrasonic additive manufacturing technology.In this paper,the preparation process of diamond/copper composites prefabricated strip by resistance welding and the ultrasonic preparation method of composites with prefabricated strip as the manufacturing unit are introduced.It provides a theoretical and experimental basis for the application and promotion of the ultrasonic fabrication technology of particle reinforced metal matrix composites.Firstly,the three-dimensional grid structure was designed to realize the spatial constraint and fixation of diamond particles between composite layers,and the diamond was closely embedded in copper matrix through the size matching of diamond particles and copper grid structure,which created the basic conditions for the resistance welding preparation process of diamond/copper composites prefabricated strip.The strategy for constructing a "sandwich" structure diamond/copper composites prefabricated strip was proposed,and the conductivity of the diamond particles was improved by surface modification.In addition,by applying the joule thermal effect of graphite electrode,the control of heat distribution and temperature rise and fall rate in the preparation process of composites prefabricated strip resistance welding was realized,and the interlayer bonding performance of composites prefabricated strip was improved.The role of diamond surface metallized coating in the preparation process of composite prefabricated strip was observed and studied through high-speed photography and infrared temperature monitoring.It was found that the metallized coating not only guides current and improves the interlayer bonding performance of the preforms,but also serves as a bridge connecting the copper matrix and diamond.The response surface methodology was used to take the average thickness of the composite prefabricated strip as the response value.The processing parameters of diamond/copper composites resistance welding under the particle size of 60 μm,100 μm and 150 μm were optimized,and the optimal combination of processing parameters was obtained.Secondly,based on the diamond/copper composites prefabricated strip prepared by the graphite electrode thermal compensation resistance welding method,and taking it as the raw material structural unit of the diamond/copper composites,the ultrasonic preparation of Cr-coated-diamond/copper composites was realized.The influence of key process parameters such as ultrasonic amplitude,normal pressure and preheating temperature on the interlayer bonding performance of the composites was studied through single factor variable test.Research has confirmed that ultrasonic amplitude and normal pressure have a significant impact on the distribution of diamond and interlayer bonding properties in diamond/copper composites.Large welding parameters can lead to displacement and mutual contact of diamond particles between the Cu layers.Finally,Cr-coated-diamond/copper composite material with a thermal conductivity of 428.07 W/m·K was successfully prepared.Finally,a simulation model for the ultrasonic preparation process of Cr-coateddiamond/copper composites was established using finite element method.The interface evolution process between diamond particles and copper matrix was simulated and analyzed using a ductile damage model.The plastic deformation process,behavior,temperature field distribution,and stress distribution of the matrix during the preparation process were studied,It was found that the gap area between diamond and copper mesh structure is prone to the formation of gap defects and under bonding interfaces.The ultrasonic energy transfer process and interface evolution mechanism during the preparation process were analyzed.It was found that the ultrasonic preparation process of Cr-coated-diamond/copper composites can be divided into oxide film crushing and deformation initiation stage,surface bonding stage,volume bonding and recrystallization stage.Under high-frequency ultrasonic shear,dynamic recrystallization occurs at the interface based on the Bauschinger effect,resulting in an increase in dislocation density and grain refinement.The simulation results of equivalent plastic strain and the interface EBSD test results have been mutually confirmed.