Solid- and Liquid-Solid Reactions in Aluminum-Coated Titanium Substrate Fabricated by Using Explosive Energy

抄録

A Ti plate coated with an Al foil with a thickness of 100 μm was prepared by using explosive energy. The bonding was momentarily achieved without breaking the Al foil. This Al-coated Ti plate was heated between 898 and 1273 K in the air to investigate interfacial reactions in solid Al/solid Ti and liquid Al/solid Ti states from the viewpoint of diffusion coating for Ti materials. At 898 K, a continuous Al₃Ti layer was formed along the interface. Although the Al foil was almost replaced by Al₃Ti in a holding time of more than 32.4 ks, many defects such as void and crack were observed in the Al₃Ti layer. It is noteworthy that the thickness of the Al₃Ti layer increases in proportion to the holding time in the early stage, and then, to the square root of the holding time. On the other hand, the specimen, which was heated at a temperature above the melting point of Al, showed a porous structure of Al₃Ti via an Al + Al₃Ti duplex state. The holding time to produce the porous structure became short with increasing heating temperature. It is expected that the Al + Al₃Ti duplex structure is more beneficial as a surface coating layer formed by the interfacial reaction. To replace the Al foil region by such a duplex structure, continuous heat treatment was performed between 1023 and 1073 K. There were no defects in the Al + Al₃Ti duplex region on the Ti plate, and its maximum Vickers hardness was approximately 3 times higher than that of the Ti plate.