A MICROSCOPIC PHASE–FIELD STUDY FOR THE INFLUENCE OF ORDERING ENERGY ON Cr SUBSTITUTION BEHAVIOR IN Ni75Al15Cr10 ALLOY

The microscopic phase–field model based on long range order (LRO) method was proposed to study Cr substitution behavior in Ni75Al15Cr10 alloy aged at 1073 K. This has been demonstrated by short range order (SRO) methods and experiments such as pseudo–potential, Monte Carlo method and Rutherford back scattering analysis (RBS). Adding ±4 meV to the ordering energy of Ni–Al, Ni–Cr and Al–Cr in 1st—4th nearest–neighborhoods is used to describe the influence of potential field on substitution. On the analysis of atomic images, the order parameters and Cr occupation probabilities, results show that there are coexisted Ni–Al anti–site and Cr substitution for Ni and Al in L12 ordered phase, and Cr substitution occurs much more often than Ni–Al anti–site. As the ordering energies of Ni–Al and Ni–Cr in 1st and 3rd nearest–neighborhoods increase, there is a more increasing tendency of substitution of Cr for Al than for Ni. For the 2nd and 4th nearest–neighborhoods, the ordering energy makes the tendency of substitution of Cr for Ni increase. Otherwise, with the 1st and 3rd nearest–neighborhoods ordering energies of Al–Cr increasing, the tendency of substitution of Cr increases for Ni but decreases for Al, which is opposite to the cases for the 2nd and 4th nearest–neighborhoods.