軸受鋼SUJ2 と Ti-6Al-4V 合金の拡散接合部の強度特性におよぼす界面形成相の影響

抄録

Diffusion bonding of SUJ2 and Ti-6Al-4V has been carried out in the bonding temperature range from 1173 to 1273K for 3.6 ks at the bonding pressure of 1.96MPa. The effects of the reaction phases formed at the bonding interface on the bonding strength were analysed. Main results obtained were as follows:
(1) With increasing bonding temperature, the species of the main reaction phases at the bonding interface change from FeTi₂ to Fe₂Ti via FeTi by the diffusion of iron atoms of the SUJ2 into the Ti-6Al-4V phase.
(2) With increasing the bonding temperature, tensile strength and elongation of the joints first increased and then decreased, whereas the maximum Vickers hardness of the reaction phase first decreased and then increased. Therefore the changes in the strength properties were well correlated with the change of the maximum Vickers hardness of the reaction layer.
(3) On the other hand, diffusion of Ti, Al and V atoms of the Ti-6Al-4V into the SUJ2 phase was comparatively small. It can be explained by the formation of a TiC phase at the bonding interface of the SUJ2 side which protects the diffusion of these atoms. In spite of its high Vickers hardness, fracture did not occur at the TiC phase because of its small width under 3μm.
(4) Fractured parts of the tensile tests of joints were the reaction phase part mainly composed of the above mentioned Fe-Ti intermetallic compound. Therefore, tensile strength and elongation of the joints were found to be influenced mainly by the species of intermetallic compound phase.