Diffusion Welding of Copper to Aluminum(Materials, Metallurgy, Weldability)
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Diffusion welding of copper to aluminum has been carried out in a vacuum environment. The microstructure of the bonding zone is examined in detail with several metallographic methods to make clear the important factor which affects the mechanical properties of the joint. Results obtained are summarized as follows: 1) An intermetallic compound layer is observed which can be divided into three characteristic region I, II and III. The intermetallic compounds of θ and γ_2 are formed in I and II region, respectively. The hardness of region II is the highest of the regions. 2) The growth of the intermetallic compound layer is considered to be controlled by the atomic diffusion and the increase in the intimate contact area between the faying surfaces. The diffusion process becomes more important with the increase in welding temperature. 3) In the earlier stage of welding (shorter welding time), the tensile strength of joint increases with the rise of welding temperature, time and pressure. This stage is considered to be a process where the intimate contact between the faying surfaces is developed. 4) In the later stage of welding (longer welding time), the tensile strength of joint approaches to a constant value (2〜3kg/mm^2) much lower than that of aluminum base metal. This tendency is observed for the thickness of the intermetallic compound layer greater than 15〜20μm. In this case, fracture is developed in the intermetallic compound layer, but not at the welding interface. The strength of joint welded in this stage is considered to be controlled by the strength of the intermetallic compound layer.
- Transactions of JWRI
Transactions of JWRI 8(1), 77-84, 1979-06