Abstract
Titanium and magnesium alloys have been applied as structural and biological materials because of their superior high specific
strength. However, since they are thermodynamically immiscible, effective bonding methods have not been established. We have
recently designed a dealloying bonding method to join thermodynamically immiscible metals. In the dealloying method using
metallic melt, only specific components are selectively leached from the precursor alloy into the metallic melt by differences
in chemical interactions, while the remaining components self-assemble into a porous form. When the metal melts solidifies,
bicontinuous microstructure of the residual phase and the solidified phase is formed, which mechanically bonds the immiscible
phase. We have already succeeded in bonding pure Fe and pure Mg by this method, and here we report the extension of the
usefulness of this technique to joining pure Ti and pure Mg in dissimilar materials. To avoid melting the entire Mg matrix, eutectic
melting of Cu and Mg was used to locally generate liquid metal dealloying at the bonding interface. Although precursor layers and
by-products of the dealloying can remain at the bonding interface, these can be eliminated by optimizing the bonding conditions,
such as bonding temperature, time, precursor layer thickness, and pressure. When these brittle layers are eliminated from the
bonding interface, the tensile fracture strength is highest, yielding a strong mechanical bonding strength that fractures with the
Mg base metal. This study offers the possibility of joining other two immiscible metals, and in addition may provide fundamental
knowledge for overcoming difficult bonding of practical alloys.
