Solubility of O and Ca in molten Ti-Cu alloys equilibrated with a CaO-MgO-CaCl₂ flux at 1473 K

Solubility of Ca and O in molten Ti-Cu alloys equilibrated with a CaO-MgO-CaCl₂ ternary flux in CaO or MgO crucibles at 1473 K was analytically investigated. The Equilibrium constant of deoxidization reaction by dissolved Ca can be determined as follows: CaO_{(s)in CaO crucible} = Ca_{in Metal} + O_{in Metal}, - 3.25 = logK, K= (a_ca · a_O) / (a_CaO) Moreover, from the investigated partial pressure of O around the reaction cell, an equilibrium constant of dissoluble reaction of O in the molten alloys can be determined as follows: 1/2O₂ = O_{in Metal}, 16.08 = logK, K= [a_O in Metal]/(P_O2^1/2) If it is possible to use an equilibrium constant of calcia formation published as a thermodynamic data book, an equilibrium constant of dissolution reaction of calcium into molten alloys can be determined as follows, Ca_{in Flux} = Ca_{in Metal}, -2.29 = logK, K= [a_{Ca in Metal}] / (a_{Ca in Flux}) The activity of CaO in the CaO-MgO-CaCl₂ ternary flux equilibrated with a MgO crucible is determined as 0.76 compared to the normal state (a_CaO = 1) using a CaO crucible. This is obtained from the difference of the equilibrium constants of CaO formation using CaO and MgO crucibles, as expressed by the relation: logK = logK′ + loga_CaO.