Research On Calculation Of Phase Diagram For Fe-1.0Mn-0.1V-0.2C And Fe-1.5Al-1.5Cr-C Alloy

Computational Materials Science is a new subject, which came into being with the large development of thermodynamics, statistic mechanics, the solution theory and computing science and technology. As a part of Computational Materials Science, Calculation of Phase Diagram(CALPHAD) technology have guide meaning for new materials development and heat treatment process. Today, many developed countries have owed their commercialization software in this field, which has been put into application. CALPHAD research in our country started much later, but in the past decade considerable progress has been made in the field. Although there is still not commercialization software in our country, much exploration work has been done and put into application. In the paper, based on the principle of phase diagram calculation and CALPHAD technique, a program of a kind of CALPHAD has been finished using Borland C + + Builder6.0 language.On the foundation of the basic principles of phase diagram calculation, we calculated the mole fraction of each element of each phase of Fe-1.0Mn-0.1V-0.2C and Fe-1.5Al-1.5Cr-1.5C four-component alloy using two methods, one called equal chemical potential, and another free energy minimization method. Our calculation model is: using regular solution model to describe liquid(L) phase, and using sub-lattice model to describe body-centered cubic(BCC) phase, face-centered cubic (FCC) and cementite (CEM). According to our physical model, for each phase we construct an expression equation of free energy. Then, settling the thermodynamic data of the two quaternary alloys in above equation, the equation is solved by Newton method and Simplex method in C++language code on our computer.In addition, because contraction coefficient and punishment coefficient must be chosen by experience, but small changes of these two values will greatly influence the results, in this study, a mathematical method called Uniform Design Method is selected to get the optimal value, and the values of contraction coefficients areα=1,β=0.5,γ=2.0, the value of punishment coefficients areμ1=1×106,μ2=1×108.