In-grain phase separation and structural ordering in Fe–Ga alloys seen from reciprocal space

Abstract

Single crystal synchrotron diffraction was used for detailed analysis of ordering effects in alloys with a nominal composition of Fe80.5Ga19.5 and Fe73.1Ga26.9. The first composition manifests a disordered average A2 structure with local fluctuations resembling a D03 ordering motif in the lengthscales of ~50 Å. In Fe73.1Ga26.9 alloy ordered over a long range, a D03 matrix coexists with ~100 Å inclusions of a new ordered phase, presumably hexagonal with lattice parameters a ≈ 8a0 and c ≈ 12a0, where a0 = 2.87 Å is the unit cell dimension of body-centered cubic Fe.