STUDY ON DISSIMILAR METAL BONDING WITH NANO-METER SIZE CRYSTAL INTO BOND INTERFACE AND REACTION AT BOND INTERFACE BY HEAT TREATMENT

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We made clad materials such as Al/Ti, Al/Steel and Al/Cu using the vacuum roll bonding apparatus developed by us. Effects of roll reduction and bond temperature on bond tensile strength of these clad materials, optical microstructures and high resolution TEM structures on the bond interfaces between dissimilar metals have been investigated. And also, changes of microstructure on the bond interface between the dissimilar metals have been observed after heat treatments. Main results obtained are as follows. (1) Bond tensile strength of these clad materials increased with increases of reduction and bond temperature. (2) Amorphous, nano-meter crystal structure and inter-metallic compounds in very thin thickness were observed using TEM. (3) The bond mechanism of the vacuum roll bonding method is considered as below. The softer metal composed the clad material is elongated largely compared with the harder metal during the bonding and friction heat is generated at the bond interface. The bond interface is abruptly cooled and the amorphous and nano-meter crystal are formed after bonding. (4) Inter-metallic compounds grew up accordingly by the diffusion controlled after heat treatments.