Structures and phase transitions in Fe–Ga–Al alloys

Evolution of structural phases and microstructural cast state of Fe$_{100-(x+y)}$Ga$_x$Al$_y$ compositions in the range of 17 $\le(x+y)\le$ 39 at.% was studied in neutron diffraction experiments performed with high resolution and in continuous temperature scanning mode when heated to $\sim$ 900$^\circ$C and subsequent cooling. It is established that the structures of the cast states of triple alloys in the studied range of Ga and Al content basically repeat the structure of the double compositions Fe$_{100-x}$Ga$_x$ up to $x\approx$ 30 and Fe$_{100-y}$Al$_y$ up to $y\approx$ 50. Namely, only cubic phases (A2, D0$_3$ and B2) are observed in them, and hexagonal (A3, D0$_{19}$) and monoclinic (such as Fe$_{13}$Ga$_9$ or $\alpha$-Fe$_6$Ga$_5$) there are no phases characteristic of the Fe–Ga system. The expansion of the range of formation of cubic phases formed on the basis of the BCC cell in ternary alloys in comparison with Fe$_{100-x}$Ga$_x$ indicates the role of Al in the stabilization of these structures.