Papers by Author: Hirotaka Imaeda

Abstract: Dissimilar joining of Al alloys and steel was carried out using diffusion bonding process. The effects of Si and Mg contents of Al alloys and bonding parameters on the interfacial reaction were fundamentally investigated. While the reaction layers consisting of Fe-Al type intermetallic compounds (IMCs) formed at the interfacial region, in the joint with Al alloys including 1mass% Si or more a ternary Fe-Al-Si IMC layer formed at the Al alloy side. The growth of the reaction layers followed the parabolic growth low. A maximum joint strength was obtained at an average reaction layer thickness ranging from 0.5 to 1μm. The thicker reaction layer caused the fracture of the joints at a lower stress because of brittleness of the IMCs, and the thinner reaction layer including un-bonded interface also resulted in a low joint strength. As a result a thin and uniform reaction layer including less un-bonded interface can realize a high joint strength. Since the Fe-Al-Si IMC layer uniformly formed more rapidly than the binary Fe-Al IMCs in the joint with Al alloys including 1mass% Si or more, a higher joint strength was obtained at a thinner average reaction layer. As a result, it was found that the chemical compositions of 6000 series Al alloy controlled to be Mg (0.6 to 1.0mass%) and Si (more than 1.0mass%) were appropriate to obtain the better bonding characteristics.

Abstract: In the present study, we fundamentaly analyzed the interfacial reaction and evaluated the joint strength in dissimilar diffusion bonding of Al alloys to steels. The growth of the reaction layer consisting of FeAl3 and Fe2Al5 intermetallic compounds followed the parabolic growth low. The joints with 5000 series Al alloys had a higher growth rate of the reaction layer than the joints with A6061 Al alloy. The joints of A6061 Al alloy to HT980steel had the lowest growth rate of the reaction layer. The joint strength depended on the thickness of the reaction layer. The A6061 Al alloy/steel joints had the maximum joint strength at around 1µm of average reaction layer thickness.