Abstract No.:	966
Scheduled at:	Tuesday, June 19, 2007, Brüssel 4:20 PM Diffusionsschweißen, Mikro- und Nanotechnologie, Korrosion und Korrosionsschutz, Integrierte Fertigung Diffusion bonding, micro- and nanotechnologies, corrosion and corrosion protection, integration of brazing into the production process
Title:	The Influence of Metal Surface Roughness on the Diffusion Welding of Carbon Steel to Aluminum
Authors:	M. Kamal Karfoul* / Al- Baath University, Homs, Syria, Syria Gordon Tatlock / The University of Liverpool, UK Robert Murray/ The University of Liverpool, UK
Abstract:	The standard processing conditions for the diffusion welding of carbon steel to aluminum involve the pressing together of the two metals below the yield point of aluminum while heating in a vacuum or reducing atmosphere for a calculated time to induce the diffusion process at the interface between the welded surfaces. The process temperature and other conditions during the diffusion welding of this couple, cannot on their own, release the aluminum oxide layer from the aluminum surface, which prevents the diffusion process at the interface. In this paper, the diffusion welding of carbon steel to aluminum was studied under normal ambient atmosphere conditions. By using electron microscopy and EDX analysis to observe the samples after different stages of welding, it was found that the aluminum oxide layer on the aluminum surface was broken down as a result of plastic deformation of the roughened surface. This plastic deformation is caused by the welding pressure on the metal welding couple. By calculating the critical strain on a thin aluminum oxide layer caused by the roughness of the steel surface during welding, the limits on the smoothness of a carbon steel surface, which could be welded successfully, were determined. Hence the necessary conditions for the successful diffusion welding of a carbon steel/aluminium couple are a minimum surface roughness of the carbon steel and plastic deformation of the aluminum at a diffusion temperature which should be less than 660oC, and a vacuum or reducing atmosphere in the welding chamber would appear to be unnecessary.

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