ok basically the titanuim is usally combined with boron, but not always. the titanium acts as seeding effect, on cooling the titanuim having a higher metling point colls down and acts as neucleating zones, the more titanium the greater the zones. These help promote smaller grains as they solidify,
Care has to be taken when using titanium in furnaces, as it has a tendancy to drop out of solution and sink to the bottom of the pot, a good mix with a dry stirrer should help avoid this.