CHEMICALLY-INDUCED MIGRATION OF LIQUID-FILMS AND GRAIN-BOUNDARIES IN TIN-NI-(TIC) ALLOY

Liquid films and grain boundaries in the TiN-Ni system migrate when carbon atoms are added as TiC. Ti(NC) solid solution grows at the expense of TiN solid through liquid film migration (LFM), and its general characteristics are similar to those of the previously investigated Mo-Ni and W-Ni systems. But, in this system, precipitating solid-liquid interfaces of migrating liquid films show faceting, which is caused by orientation-dependent interface-controlled reactions. With an increase of added TiC, the migration rate increases parabolically with the observed lattice parameter difference between the TiN and Ti(NC) solid, which is in agreement with the prediction of the coherency strain model. Chemically induced grain-boundary migration (CIGM) also occurs, together with LFM. The results in this study show that LFM and CIGM occur in a system having relatively strong covalent bonding.