Interfacial phases in diffusion bonded joints of Al X alloys (X=Mg, Si, Mn, Zn, Cu) - Diffusion bonding mechanism of Al alloys by transmission electron microscopy (Report 5)

The effects of alloying elements on the morphology of interfacial oxides in the diffusion-bonded joint have been investigated mainly by TEM observations for Al binary alloys containing 0.06 2.0 at%Mg, 1.0 at%Si, 0.5 at%Mn, 1.0 at%Zn, and 1.0 at% Cu. At the joint interfaces of the Al binary alloys except for those of the Al Mg system, continuous amorphous oxide films were observed at all bonding temperatures employed in this investigation. At the joint interfaces of the Al-Mg alloys, as described in a previous paper, the oxide at the joint interface altered gradually from amorphous films to crystalline particles 10-100 nm in size as the bonding temperature was increased. The difference in the behavior of interfacial oxide between the Al-Mg alloys and those of the other alloys can be explained thermodynamically by assuming that crystalline oxides were formed through reductive reactions of the superficial oxide film of Al by Mg. EDS analyses of the amorphous oxide film at joint interfaces of the alloys revealed that Mg atoms were concentrated in the amorphous oxide film of the Al-Mg alloys prior to the formation of the crystalline oxide particles, whereas no concentration of other alloying elements could be detected in the amorphous oxide film of the other alloys.