Kinetics of formation and coarsening of nanoporous α-titanium dealloyed with Mg melt

The transition behavior from a Ti–Cu alloy to nanoporous α-Ti, the kinetics of the dealloying reaction, and the coarsening of nanoporous α-Ti were studied, and the mechanism of dealloying with a metallic melt was investigated. When a Ti50Cu50 alloy disk was immersed in a Mg melt, the Cu content decreased from the surface of the disk, and transition layers of α-Ti and Ti2Cu were formed. The growth of the transition layers followed a parabolic law and the activation energy was close to those reported for the diffusion of solute atoms in liquids, suggesting that diffusion of Cu in the Mg melt mainly contributed to the rate-controlling process for the dealloying reaction. The temperature and time dependences of the ligament size followed a power law with an exponent of 4, suggesting that surface diffusion plays an important role in coarsening. All of these results are consistent with those reported for dealloying in aqueous solution, indicating that the underlying dealloying mechanism in a metallic melt is similar to that in aqueous solution.