Estimation of point defect formation energies in the L1{sub 2}-type intermetallic compound Ni{sub 3}Ga

• Published in: Scripta materialia 2000-02, Vol.42 (6)
• Main Authors: Semenova, O.P., Yuan, W., Krachler, R., Ipser, H.
• Format: Article
• Language: English
• Subjects: CRYSTAL DEFECTS; GALLIUM ALLOYS; INTERMETALLIC COMPOUNDS; MATERIALS SCIENCE; NICKEL ALLOYS; STATISTICAL MODELS; THERMODYNAMICS
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/S1359-6462(99)00391-7

There has been considerable interest in recent years in the properties of intermetallic compounds with the cubic L1{sub 2}-structure. One prominent example is the compound Ni{sub 3}Al which has gained technological importance in the development of the so-called superalloys due to some of its unique properties like high temperature strength and excellent corrosion resistance. Much less is known about the properties of the isostructural compound Ni{sub 3}Ga which may have similar interesting properties even if its (peritectic) melting point is considerably lower. This lack of information is certainly caused by the much higher cost of metallic gallium, nevertheless, Ni{sub 3}Ga might still be of interest for specific applications. Unfortunately, the number of experimental data points to be used for the evaluation was extremely limited, and the possible existence of vacancies on the two sublattices was a priori completely neglected. Therefore, it was considered worthwhile to determine carefully the composition dependence of the gallium activity in the Ni{sub 3}Ga-phase and to apply a newly developed statistical-thermodynamic model; this would not only yield a more accurate disorder parameter (since it would be based on a higher number of experimental data points) but also values for the energies of formation of the various point defects.