Experimental and first principle calculation study on titanium, zirconium and aluminum oxides in promoting ferrite nucleation

Double thermal diffusion bonding experiment, electron probe microstructure analysis and first principle calculation were used to investigate the potency of titanium, zirconium and aluminum oxides in steels in promoting ferrite formation. Oxides studied here include TiO, Ti2O3, Ti3O5 and TiO2 as well as ZrO2 and Al2O3. During thermal diffusion bonding experiment, the specimen was first held at 1200 °C for 10 min and then rapidly cooled to the dual phase region of the matrix steels for isothermal holding, followed by direct quenching to room temperature. The potency and/or efficiency of the oxides in promoting ferrite nucleation was differentiated by the choice of different matrix, the austenization temperature and the isothermal holding temperature within the dual phase region. Mn was found in the interior of all the oxides except TiO with Fe-C-Mn steel as the matrix. Ni was not found in the interior of all the oxides with Fe-C-Ni steel as the matrix. The promoting ferrite nucleation induced by Ti2O3 and Ti3O5 is explained by Mn-depletion zone formation. The promoting ferrite nucleation induced by TiO2 and ZrO2 can be explained by Mn and/or C-depletion zone formation. The promoting ferrite nucleation by Al2O3 can be explained by Mn depletion zone formation and/or lower interfacial energy theory.