Experimental Investigation And Thermodynamic Description Of The Ni-V-Zn Ternary Phase Diagram

Silicon-containing structural steel is one of the most widely used steels in modern industrial production and construction.The common method to reduce the corrosion of steel is the application of hot dip galvanizing technology.However,in the case of structural steel hot-dip galvanizing,silicon reactivity occurs,resulting in a decrease in coating quality and corrosion resistance.Adding a certain amount of alloying elements in the zinc bath can improve the microstructure and properties of the coating.Among them,the metal vanadium?V?and nickel?Ni?are effective in inhibiting the addition of silicon reaction elements in silicon-containing steel,but the inhibiting effect on the silicon reaction of active steel with higher silicon content?Q235,Q345,etc.?is not good.Related research shows that the synergistic effect of Ni-V on active steel silicon with high silicon content was significant,which not only made the coating thinner,but also significantly improves the corrosion resistance and oxidizing resistance of the coating.In this work,the phase equilibrium relationship of Ni-V-Zn ternary system was measured by experimental method,and the ternary system was optimized and calculation by CALPHAD method.Thus,it is possible to provide scientific foundation for the composition design and process parameters optimization of active steel hot dip galvanized coating of active steel.The samples of equilibrium alloy of the Ni-V-Zn ternary system have been analyzed by means of scanning electron microscope with energy dispersive spectrometer?SEM-EDS?,and x-ray power diffraction?XRD?,and the isothermal sections of the Ni-V-Zn ternary system at 450? and 600? have been measured.There are ten three-phase equilibrium regions in the isothermal section of Ni-V-Zn ternary system at 450?,namely:L+?+VZn₃,?+VZn₃+?,VZn₃+?+V₄Zn₅,?+V₄Zn₅+?-V,Ni₂V₇+?+?-V,Ni₂V₇+?+?,?+?+?₁,?+?₁+Ni₂V,?₁+Ni₂V+Ni₃V,?₁+Ni₃V+?Ni?.Nine three-phase zones in the isothermal section at 600?,i.e.L+VZn₃+?,VZn₃+?+V₄Zn₅,?+V₄Zn₅+?-V,Ni₂V₇+?+?-V,Ni₂V₇+?+?,?+?+?₁,?+?₁+Ni₂V,?₁+Ni₂V+Ni₃V,?₁+Ni₃V+?Ni?.No ternary compounds were found in the either isothermal section.In the 450? isothermal section,the solubility of V in?,?and?₁ are 1.28,3.29and 4.1 at.%,and the solubility of Zn in Ni₂V₇,Ni₂V,?and Ni₃V are 0.48,1.2,4.3and 2.9 at.%,respectively.In the 600? isothermal section,the solubility of V and Ni in the liquid phase L??-Zn?are 2.2 at.%and 0.9 at.%,respectively,and the solubility of V in?and?₁ are 2.5 and 4.3 at.%,Zn The solubility in the Ni₂V₇,Ni₂V,?and Ni₃V phases are 0.5,1.2,9.48 and 3.2 at.%,respectively.In the isothermal section at 450? and 600?,the solubility of Ni in VZn₃ and V₄Zn₅ is very small,less than 0.2at.%.In combination with the experimental phase diagram of this work,the experimental data and thermodynamic parameters of the three binary systems reported in the literature were collected and sorted out systematically,and the thermodynamic optimization calculation of the Ni-V-Zn ternary system was carried out by using CALPHAD technology:substitutional solution model was used for the solution phase,and sublattice model was used for compounds?and Ni₃V to simulate?Ni,V?₁₀?Zn,V?₄?Zn,Ni,V?₁₆6 and?Zn,Ni,V?₃?Ni,Zn,V?₁,?₁ is described by sublattice?V,Ni,Zn?₁?Ni,Zn?₁ to adapt to multi-component systems.A set of self-consistent thermodynamic parameters for the Ni-V-Zn ternary system was obtained with a reasonable agreement between the experimental and calculated results.In addition,the liquid phase surface projection of the Ni-V-Zn ternary system is predicted by using the Ni-V-Zn ternary thermodynamic databas.