Formation of solid solutions of gallium in Fe–Cr and Fe–Co alloys: Mössbauer studies and first-principles calculations

• Structure features of the formation of quasibinary solid solutions Fe–Co–Ga and Fe–Cr–Ga are found.
• The first-principles calculation of mixing and solubility energies for Ga in an Fe–X alloy are given.
• Ga handicaps the processes of phase separation in the Fe–Cr system and ordering in the Fe–Co system.
• Preference of Ga entering in the neighborhood of a second element can help study multielement alloys.

Investigation of Ga influence on the structure of Fe–Cr and Fe–Co alloys was performed with the use of Mössbauer spectroscopy and X-ray diffraction methods. The experimental results are compared with results of first-principles calculations of the mixing and solubility energies for Ga in an Fe–X (X = Co, Cr) alloy both in ferromagnetic and paramagnetic states. It is shown that Ga mainly goes into the solid solutions of the base alloys. In the alloys of the Fe–Cr system, doping with Ga handicaps the decomposition of solid solutions, observed in the binary alloys, and increases its stability. In the alloys with Co, Ga also favors the uniformity of solid solutions. The results of the first-principles calculations testify in favor of a preferable dissolution of Ga in the FeCo regions of a multicomponent structure rather than FeCr regions, both types of regions being in the ferromagnetic state at the temperature of annealing. The analysis of Mössbauer experiments gives some grounds to conclude that if, owing to liquation, clusterization, or initial stages of phase separation, there exist regions enriched in iron, some amount of Ga atoms prefer to enter the nearest surroundings of iron atoms, thus forming binary Fe–Ga regions (or phases).