Calculation of superalloy phase diagrams: Part II
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AND HARVEY NESOR
Explicit descriptions of the Mo-A1, Fe-A1 and Ni-A1 systems have been developed and combined with descriptions of seven binary systems developed previously to compute significant numbers of isothermal sections in the Mo-A1-Cr, Ni-A1-Fe, Cr-Ni-A1, A1-Ni-Mo and Ni-A1-Ti systems. Comparison of these calculations with limited experimental data yields good results and provides considerable insight into the stability of the bcc phase in these systems. The computations provide detailed information on tie-line configurations and melting minima in these systems. U T I L I Z A T I O N of computer-based methods for calculation of ternary phase diagrams has been facilitated by developing explicit descriptions of the lattice stability of the pure components and the solution and compound p a r a m e t e r s of the component binary systems. ~-s The first paper of this s e r i e s 7 demonstrated the usefulness of this method by calculating the t e r nary phase diagrams for seven important superalloy systems based on binary systems defined earlier. In the current study, three additional binary systems (Mo-A1, Fe-A1 and Ni-A1) were analyzed in line with observed phase equilibria 8-1~ and thermochemical data n'~2 and combined with seven previously defined systems where explicit functions for the excess free energy of solution phases have been defined in conformity with experimental thermochemical and phase diagram data (i.e. Ni-Fe, Cr-Ni; s A1-Cr; 4 Mo-Cr, Ni-Mo and Ni-Ti; 5 and A1-Ti6). These descriptions have been employed to calculate significant numbers* *A substantial number of calculated isothermal sections submitted by the authors in the original manuscript were deleted at the request of the editorial review committee. These isotherms are listed for each of the systems in question.
of isothermal sections in five ternary superalloy systems. The systems in question are listed below along with references to experimental studies for each case: Mo-A1-Cr, Ni-A1-Fe, Cr-Ni-A1; is A1-Ni-Mo 14'~5 and Ni-AI-Ti.za'16
I. ANALYSIS OF BINARY SYSTEMS P r i o r studies of binary systems containing aluminum have been restricted to Ti-A1, 6 Cr-A14 and Cb-A1. 4 In addition, a complete analysis of the CbA1-Cr system has been c a r r i e d out. 4 However, expansion of the range of t e r n a r y systems containing aluminum which can be considered requires analysis of the Mo-A1, Fe-A1 and Ni-A1 systems. Accordingly the present work was initiated with a consideration of these binary systems. In all cases the binary analysis was c a r r i e d out to obtain the best agreement possible with phase diagram 8-z~ and thermochemical data. n'z2 1. The Mo-A1 System Table I and Fig. 1 s u m m a r i z e the description of the Mo-A1 system along the lines outlined previously. L A R R Y K A U F M A N and H A R V E Y N E S O R are Director o f Research and Senior Scientist, respectively, ManLabs, Inc., C a m b r i d g e ,
Mass. 02139. Manuscript submitted August 2, 1973. METALLURGICAL TRANSACTIONS
The limited phase diagram data and the absence
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