純チタンと純鉄の拡散接合界面の微視的構造と接合強度

抄録

The microstructure and the interfacial strength have been studied for the diffusion bonding pairs between a commercially pure Ti and Fe-0.003 wt%C or Fe-0.015 wt%C.
The transformation of α-Ti into β-phase and the formation of intermetallic compounds (TiFe and TiFe₂) were induced by the interdiffusion in Ti/Fe-0.003 wt%C bonding pairs. During the cooling to room temperature, β-phase layer with higher Fe content retained in /β-phase, whereas β-phase layer with lower Fe content transformed into α'-Ti martensite. The specific crystallographic orientation relationship ; (0001)_TiFe2//(101)_α-Fe [1120]_TiFeTiFe₂//[111]_{α -Fe} (Burger's relationship) was obtained between TiFe₂ and α-Fe.The result indicates that TiFe₂ was formed in α-Fe by the diffusion of Ti-atoms.
In Ti/Fe-0.015 wt%C bonding pairs, /β-transformed layer and intermetallic compound layer were not observed at the bonding temperatures below 1 073 K. In this case, TiC precipitates formed along the interface and they hindered the interdiffusion of Ti- and Fe-atoms. However β-transformed layer and intermetallic compound layer formed at the bonding temperature above 1 123 K.
The interfacial strength of Ti/Fe-0.003 wt%C bonding pairs depended on the width of intermetallic compound layer ( W_IM). At the initial stage of bonding the strength was very low due to the inadequate diffusion, but it increased to the level of 300 MN m^-2 in the W_IM range between 0.4 and 1.2 μm. The strength decreased rapidly again after the growth of intermetallic compound layer thicker than 1.2 μm.