Thermodynamic Calculation Of The Al-Zr-(Li,V)Ternary System

Aluminum is the most abundant metal in the earth and it is widely used for aviation,aerospace and etc.Recrystallization process of aluminum alloys can be hindered by adding Zr element,which can improve the mechanical properties.It is reported that adding lithium element to Al-Zr alloy can improve its specific strength and specific rigidity and adding vanadium element to Al-Zr alloy can reduce the number of discontinuous precipitations.With the development of computers,them have had a strong ability for computing.This make computers can be used for predicting the performance of materials and material design.However,this process must be supported by a sound database.Therefore,it is necessary to establish Al-Zr-(Li,V)system thermodynamic database to guide alloy design for aluminum and its alloys.The Al-Zr and Al-Li binary systems have been reassessed based on the latest experimental data from literatures using the CALPHAD method and the Thermo-Calc software package.On this foundation,together with the thermodynamic assessment of the Li-Zr,Al-V and V-Zr binary system and the experimental phase relations of the Al-Zr-Li and Al-Zr-V ternary system,these two ternary systems have been assessed.The excess Gibbs energies of solution phases,including liquid,bcc,fcc and hcp,were described by sub-stitutional solution model and expressed by the Redlich-Kister polynomial.The stoichiometric compounds,i.e.Al4Zr5,Al2Li3,A14Li9,Al21V2,Al45V7,Al23V4 and AlLi2Zr,were modeled as stoichiometric model and the non-stoichiometric compounds,Al32r.Al2Zr、Al3Zr2、AlZr、Al3Zr4、Al2Zr3、AlZr2、AlZr3、AlLi2、Al8V5、Al3V、V2Zr and AlLix+yZr5-x,were described with different sublattice models.Due to the atomic occupancy of the ternary compound T is not certain,stoichiometric model has been used to describe the T compound.Basing on the recent experimental results in literatures,the Al-Zr binary system has been reassessed and the thermodynamic parameters of the Al-Li binary system from the current literature has been revised in this work.New thermodynamic parameters of the Al-Zr and Al-Li binary systems have been obtained.The Al-Zr and Al-Li binary phase diagram calculated through the parameters mentioned above agree well with the experimental ones.In addition,the calculated formation enthalpies of the compounds in Al-Zr binary system,the mixing enthalpies of liquid phase in Al-Zr binary system and the formation enthalpies of the compounds in Al-Li binary system are also in good agreement with the literature data.The isothermal section at 470K of Al-Zr-Li system and the isothermal section at 1073K of Al-Zr-V system have been calculated in this work,which were reasonable agreement with the experimental isothermal sections reported by literatures.In the assessment of the Al-Zr-Li ternary system,new phase regions,i.e.Al4Li9+AlLi2+Al2Zr,Al2Li3+AlLi2+Al2Zr and AlLi2+Al2Zr,have been found,because of the addition of AlLi2 phase in the Al-Li binary system.The predicted liquidus projection of the two ternary system was also calculated in the present work.Finally,the parameter of Al-Zr-Li and Al-Li-V ternary system have been integrated and the database of Al-Zr-(Li,V)system.A set of theoretical guidance is provided to study the designing alloy compositions and processing methods.