Effects Of Oxygen Contents In Copper On The Diffusion Bonding Interface Of Copper/Steel

In this paper, copper-steel bimetallic samples were made by a cold drawing and then a diffusing process. The microstructure and element distribution of the interface of copper/steel bar through diffusing process and the bonded surfaces after peeling were analyzed by means of optical microscope, scanning electron microscope, energy disperse analysis of X-ray and electron probe microscope analysis. The micro-hardness and the shearing strength of bonded interface were measured. The copper bars of different oxygen concentrations were used in the tests. The conclusions as follows:The oxide didn't formed when the oxygen content of copper was lower even if the diffusion time was very long. The dispersed oxide Fe₂O₃ near the interface in the side of copper formed because of higher oxygen content in oxygen-bearing copper. The size of oxide increased dramatically with increasing diffusion temperature and prolonging diffusion time and the dispersed zone became wider by diffused at 800⁹50℃ for 0.5-16h. The possibility of oxide formation was discussed by thermodynamics analysis and the shape of oxide was analyzed.When the bonded interface was tested after peeling, the facture formed at copper side of bonded interface, which approved that copper and steel were well bonded merely by a cold drawing and then a diffusing process and the bonding strength of interface was higher than that of copper. The facture near the interface formed at the position of oxide and propagated along the interface between the oxide and the matrix, which indicated that the oxide would affect the performance of bonded interface. The interface bonding strengths were measured by shear test. The data of bonding strength was higher than lOOMPa, which shows that the interface bonding strengths attained the atom bonding and the performance of bonded interface is high.The results of scanning electron microscope and energy disperse analysis of X-ray indicated that the iron atom diffusion distance was much greater than that of copper atom. The iron atom diffusion distance in the copper was measured and the diffusion activation energy of iron atom in the copper was computed of 210kJ/mol. The relationship in quantity of the diffusion distance between diffusion temperature and time was acquired according to the distribution of Fe₂O₃.