Effect of the Roughness of Faying Surface on the Early Process of Diffusion Welding : Study of the Early Process of Diffusion Welding by Means of the Electric Resistance Measurement (Report II)(Materials, Metallurgy & Weldability)
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The early process of diffusion welding of aluminum, titanium and copper whose faying surfaces have been finished by polishing with emery paper of various grades (600〜1500) have been investigated with the electric resistance measurement. A couple of the base metal was brought into contact in a vacuum and the electric resistance across the bonding interface was measured while the couple was heated at the rate of 15℃/min. The obtained electric resistance in the heating process is analysed by using the contact parameter W(=n・S_M/S) which is derived on the basis of the constriction resistance theory. Here S_M is the total area of metal-to-metal contact spots, n their number per a unit area and S the apparent contact area. For all the bonding process of aluminum, titanium and copper, the electric resistance across the bonding interface decreased in its initial value and approached the resistivity of the base metal more rapidly in the heating process as the faying surface became roughened. According to an analysis based on the constriction resistance theory, the contact parameter in the heating process for all the base metals increased with roughening the faying surface. These results indicate that the disruption of oxide film on the faying surface, which prevents the formation of the metal-to-metal contact (as reported in a previous paper), is promoted and so the area and/or number of metal-to-metal contact spots increase as the faying surface becomes roughened. This fact can be accounted for by the model that the deformation of micro-asperities on the faying surface leads to the disruption of oxide film and the degree of the deformation increases as the faying surface becomes roughened.
- Transactions of JWRI
Transactions of JWRI 11(2), 49-56, 1982-12