THE FE-ZN-TI SYSTEM AT 450-DEGREES-C

The drawback of overthicknesses of coatings when galvanizing silicon s teels may be overcome by adding titanium to the zinc bath. In order to understand reactivities between substrates and the alloyed zinc bath, the ternary phase system Fe-Zn-Ti at 450 degrees C was investigated u sing diffusion experiments. Three kinds of diffusion couples were used (solid/solid, solid/liquid and solid/vapour under controlled pressure ) to describe the whole isothermal section at 450 degrees C. The solid -liquid reaction accurately reveals the zinc rich corner of the diagra m in connection with galvanizing. The analysis of the different phases in each coating allows to determine Ti solubilities in the Fe-Zn inte rmetallic compounds and to new equilibria in the Fe-Zn-Ti system at 45 0 degrees C. Moreover, we show that the diagram obtained, characterize d by a huge Gamma(2) domain is metastable. The stable diagram, obtaine d with long time experiments is characterized by a more restricted Gam ma(2) solid solution which extends from the Gamma(2) - FeZn4 binary co mpound to the Gamma(2) - TiFe2Zn22 ternary dress.