The effect of surface roughness on the diffusion weldability of Al, Al-Sn and Al-Sn-Mg alloys in the atmosphere and in a vacuum (about 0.1Pa) have been investigated. Welding surfaces were polished either with #800 grinding paper, or with 3μm diamond powder, or electrolytically. The welding was carried out at 773K for 3.6ks under a pressure of 2MPa. Results obtained are summarized as follows:
1) Magnesium reduces a part of the oxidation film at the interface during welding, being contained in liquid tin phase. The degree of reduction is high and the best weldability is obtained when Mg distributes homogeneously at the welding interface.
2) Grinding of surface with 3μm diamond powder is best for the homogeneous distribution of Mg.
3) Weldability is better in the atmosphere than in the vacuum. This behavior is prominent in A1-0.5Sn-lMg/Al-0.5Sn-1Mg couple polished with diamond powder.
4) When the couple mentioned above is welded under the applied experimental condition where the temperature is much lower than melting point of Al, nearly complete weldability is obtained even in the atmosphere.
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