Effect Of Diffusion Heat Treatment On Structure Of Cold-rolled Cu-Al Composite Laminate Interface

Copper and aluminum composite laminate has well heat conduction and electricconduction, so that it is widespread used in electric power, electronics, electrical appliances,machinery, metallurgical equipment, construction, automotive, energy and everyday life invarious fields. Diffusing heat treatment is used to achieve the purpose of metallurgicalbonding due to cold-rolled composite only has mechanical bond. Interface element mutualdiffusion can form diffusion interface layer with the intermetallic compound production inthe diffusion heat treatment process. This interface layer has important influence on thebonding strength of composite laminate, mechanical properties, thermal conductivity,electrical properties etc. This experiments study the effect of the diffusion heat treatmenttechnology on cold-rolled Cu-Al composite laminate interface diffusion process andintermetallic compounds generated system,then systematically analyzes the relationshipbetween composite interface diffusion layer thickness, morphology and the diffusion heattreatment technology parameters by SEM, EDS, XRD and TEM analytical tools.Experiments show that at the same heat treatment temperature, the thickness ofdiffusion layer has parabolic relation with diffusion time with diffusion time extending andthickness of diffusion layer increasing. The thickness of diffusion layer is increasing at thesame heat treatment time, and the thickness of diffusion layer has exponential relation withdiffusion heat treatment temperature increasing. Among these, annealing temperature is themajor factor that affects the diffusion layer.Intermetallic compound growth sequence: First, early in the diffusion layer, Al-Cusolid solution will be formed at aluminum side and Cu-Al solid solution will be formed atcopper side; Secondly, as the further spread, the concentration of solid solution reaches theformation of the intermetallic compound, Al₂Cu（θ） phase appears in the composite boardinterface; And then Al₄Cu₉（γ₂） phase appears in the interface close to the Cu side; Finally,AlCu（η₂） phase appears between the interface of the Al₂Cu（θ） phase and the Al₄Cu₉（γ₂）phase. That is, form the third diffusion layer. According to the Arrhenius equation, we calculate that the reaction activation energyof the Al₂Cu（θ） phase is97.44kJ/mol, the reaction activation energy of the Al₄Cu₉（γ₂）phase is182.11kJ/mol and the AlCu（η₂） phase is187.44kJ/mol, respectively. The totalreaction activation energy of the interface structure is150.91kJ/mol. And formulas todescribe the interface layers thickness and diffusion heat treatment temperature and timecan be established.