The Research On Organization Structure And Property Of Interfacial Diffusion Layer Of Cu-Al Composite Plate

This research was on the micro-structure characteristics and combination properties of interfacial diffusion layers of cold rolled copper-aluminum laminated plate by annealing heat treatment.Through annealing heat treatment for the cold-rolled copper-aluminum laminated plate,it could eliminate inner-residual stress of laminated plate,and also make the connection from mechanical combination to metallurgical combination.However,it will form a diffusion layer by the elements diffusion at the interface and associate with the generated inter-metallic compounds in the conditions of heating treatment or long-term use of thermal state on the laminated plate.This kind of inter-facial structure could influence the laminated-strength,mechanical properties,thermal conductivity and electrical properties,etc.In this paper,the formation and variation of interface layer for Cu/Al composite plate during annealing process was systematically studied.According to thermodynamic analysis and experimental research,the relationship between the formation for interface micro-structure of Cu/Al composite plate and heat treatment process was analyzed.Based on theoretical analysis,a physical model was established to describe the formation for interface micro-structure of Cu/Al composite plate,and the kinetics of interface layers was analyzed.The relationship between heat treatment process and the thickness of interface layer was established.The effect of interface layer structure on the properties of Cu/Al composite plate was studied.The performance stability of Cu/Al composite plate under service conditions was also evaluated.Based on the relationship between micro-structure of Cu/Al composite plate and heat treatment process,it can be found that the order of intermetallic compounds formation at interface during annealing process at 300-500? is Al2Cu,AlCu,A14Cu₉,Al9Cu11 and Al2Cu₃.Al9Cu11 and Al2Cu₃ cann't be found cause of dynamics in this study.According to the experimental results,it is proved that Al2Cu,AlCu and Al4Cu₉ are formed in the interfacial diffusion layer of Cu-Al composite plate,and the sequence of formation should be Al2Cu,Al4Cu₉ and AlCu.The diffusion process at the interface is as following:a[(Cu?Al?]solid solution and x[Al?Cu?]solid solution ? aluminum side solid solution layer formed Al2Cu intermetallic compound ? copper side formation Al4Cu₉ intermetallic compound ? Al2Cu/Al4Cu₉ formed the third one of the compound layer?the AlCu phase?.Through the investigation on the microstructures of the Cu-Al composite plate by diffusion heat treatment at 300 ?,400 ? and 500 ? for 1h,2h and 5h respectively,it is found the thickness of the interfacial diffusion layer increases with the diffusion heat treatment time of the copper-aluminum composite plate at different temperatures,and the thickness of the interface diffusion layer increases with the temperature increasing at the same time node.According to the relationship between the thickness of diffusion layer and the changes of heat treatment process,the general growth dynamics equation of IMC?intermetallic compound?is deduced as:It show a similar changing relationship between interfacial diffusion layers and high temperature diffusion heat treatment by annealing heated on Cu-Al at 250 ? 300 ? and 350 ?.And the relation-model between peeling-strength of Cu-Al and process of diffusion heat treatment has been established.The best bonding strength at interface is in the heat treatment process at 300 ?/6h.Through testing mechanical properties and conductivity of Cu-Al composite plate,combining with the previous interface bonding strength and best heat treatment process?300 ?/8h?,the best conditions are concluded as follows:the interface bonding strength is 1786.3N/m,the conductivity is 95.8%IACS,the tensile strength and elongation are 133.3MPa and 24.3%respectively.In order to evaluate the stability of Cu-Al composite panels by this process,the simulation test at 80 ?/1000h has been carried out.The tensile strength,electrical conductivity and interfacial diffusion layer of Cu-Al composite plate haven' t been changed obviously,it indicated that the comprehensive performance of Cu-Al composite plate under heat treatment process is quite stable.