In order to clarify the interfacial reactivity between A6061 and pre-coated metals in surface-activated pre-coating technique, the bond interface of diffusion-bonded joints of A6061 to Ag, Cu or Ni was analyzed. Diffusion bonding of A6061/Ag, Cu or Ni was carried out at 660-723K for 0-3.6ks applying 9.8MPa in vacuum. Eutectic temperature of A6061-Ag, Cu or Ni alloy was measured preliminarily by DTA technique. The lowest eutectic temperatures of A6061-Ag, A6061-Cu and A6061-Ni systems were 680±10K, 700±10K and 720±10K, respectively. SEM observation revealed that the reaction layer was formed at the bond interface. The Ag-Al, Cu-Al and Ni-Al intermetallic compounds were identified in the reaction layer. It was elucidated that the reaction layer growth could be expressed by parabolic growth law, and that the incubation time for reaction layer formation was increased in the order of Ag
