Thermodynamic Database Development for the ZrO 2 -MgO-MnO x System
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Thermodynamic Database Development for the ZrO2-MgO-MnOx System Ivan Saenko1 • Olga Fabrichnaya1
Submitted: 29 April 2020 / in revised form: 24 June 2020 The Author(s) 2020
Abstract Thermodynamic description of the ZrO2-MgOMnOx was derived for the first time using available experimental data on phase relations in air and protective gas atmosphere. Solid solution phases were modelled using compound energy formalism. The liquid phase was described by the modified two-sublattice model for ionic liquid. Solubility of ZrO2 was modelled in cubic spinel and MgO-MnO solid solution (halite structure) and therefore the Gibbs energies of Zr-containing endmembers were introduced. Ternary interaction parameters were introduced for halite, cubic spinel and cubic ZrO2 to reproduce the stabilization of cubic ZrO2 at temperatures below its stability in bounding systems and stabilization of cubic spinel at temperatures above its stability limit in the bounding systems. The obtained thermodynamic database was used to interpret results of differential thermal analysis. Keywords magnesium oxide manganese oxides phase diagrams thermodynamic modelling zirconia
1 Introduction Phase equilibria in the ZrO2-MgO-MnOx system are of interest due to several possible applications. One of them is development of TRIP steel metal matrix composite material strengthened by particles of MgO partially stabilized
& Ivan Saenko [email protected]; [email protected] 1
Institute of Materials Science, Technical University Bergakademie Freiberg, Gustav-Zeuner-Str. 5, 09599 Freiberg, Germany
zirconia (Mg-PSZ).[1] Manganese provides good adhesion bonding between the steel matrix and the Mg-PSZ ceramics.[2,3] On the other hand, manganese is one of the main alloying elements of the steel matrix and can substitute Mg in Mg-PSZ during processing of this metal matrix composite[2,4,5] thus influencing the stability of the Mg-PSZ structure. It was shown that due to Mg diffusion from Mg-PSZ into precipitate sites or the steel matrix the Mg-PSZ was destabilized and transformed into the monoclinic phase, while due to diffusion of Mn into ZrO2 particles, grains at its boundary remained cubic or tetragonal.[5] Therefore, knowledge of phase relations in the ZrO2-MgO-MnOx system is important to improve the stability of Mg-PSZ and its bonding to the steel matrix. The other possible application of the ZrO2-MgO-MnOx system is for directionally solidified eutectic materials since both bounding systems ZrO2-MgO and ZrO2-MnOx are known to form directionally solidified eutectics.[6,7] The phase relations in the ZrO2-MgO-MnOx system were experimentally studied by Pavlyuchkov et al.[8] for the first time. The investigations were carried out in air and inert gas atmosphere. It was shown that relatively small additions of ZrO2 stabilize cubic spinel in the ternary system in air at temperatures exceeding its stability range in the MgO-MnOx bounding system and compositions substantially enriched by MgO. The addition of ZrO2 also significantly extends the homogene
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