1982 Volume 51 Issue 12 Pages 1028-1035
The early process of diffusion welding of aluminum, titanium and copper whose faying surfaces have been finished by polishing with emery papers of various grades (600-1500 grade) have been investigated with the electric resistance measurement. A couple of the base metal was placed in vacuo with their faying surfaces in contact and the electric resistance ρ across the bonding interface was measured while the couple was heated at a constant rate of 15°C/min. The obtained electric resistance in the heating process is analyzed by using the contact parameter W(=nSM/S) which is derived on the basis of the constriction resistance theory. Here Sat is the total area of true metal-to-metal contact spots, N their number per a unit area and S the apparent contact area.
For all the bonding interfaces of aluminum, titanium and copper, the value of ρ decreased in its initial value and approached the resistivity of the base metal more rapidly in the heating process, as the faying surface became rougher. According to an analysis based on the constriction resistance theory, the contact parameter in the heating process for all the base metals was larger when the rough faying surfaces were used.
These results indicate that the disruption of oxide film on the faying surfaces, which prevents true metal-to-metal contact at the bonding interface (as reported in a previous paper), is promoted and so the area and/or number of true metal-to-metal contact spots increase as the faying surface becomes rougher. This fact can be accounted for by the model that the deformation of microasperities on the faying surface leads to the disruption of the oxide film and the degree of the deformation increases as the faying surface, becomes rougher.
