Effect of small additions of Ga on the structure of Fe-15 at.% Ni alloy

Impact that addition of 1%Ga to the Fe-15%Ni alloy exerts on the phase transformations and structure constituents has been studied by x-ray diffraction, scanning electron microscopy, Mössbauer spectroscopy, and magnetic susceptibility measurements. The results show that alloying with Ga changes the course and temperatures of forward and reverse martensite transformations and the very morphology formed after annealing in the two-phase region. In the Fe₈₅Ni₁₅alloy, polygonal Fe-Ni FCC precipitates enriched in Ni are observed at the boundaries of recrystallized BCC grains inhomogeneous in composition. At the same time, the microstructure of the Fe₈₄Ni₁₅Ga₁alloy consisting of martensite plates coherently connected with lath precipitates formed along the boundaries, with both structure constituents being homogeneous with respect to Ni content, is observed for the first time. Moreover, some indications are obtained to the ferromagnetic state of these lath precipitates.