Ternary alloys formed by aluminium, transitional metals and divalent metals

Abstract

A general survey has been made, by metallographic and X-ray methods, and by the examination of extracted crystals, of the constitutions of the alloys of aluminium and zinc with iron, cobalt and nickel, of aluminium and magnesium with cobalt, and of aluminium and beryllium with manganese and iron. In the latter two systems, new ternary compounds Mn 3Be2Al 15 and Fe 3Be7Al 7 have been discovered in equilibrium with the aluminium-rich solid solution. No ternary compounds in equilibrium with the aluminium-rich alloys occur in the other systems studied; an unidentified ternary phase separates from zinc-rich alloys in the system Al-Ni-Zn, but does not enter into equilibrium with the zinc-rich solid solution. The outstanding feature of the system Al-Co-Zn is the deposition from zinc-rich melts, at low temperatures, of the high-melting phases CoAl and Co 4Al 13 in addition to Co 2Al 9; these phases persist in equilibrium with the zinc-rich solid solution. Similarly in the system Al-Ni-Zn, Ni 2Al 3 as well as NiAl 3 is found in zinc-rich alloys, while in the system Al-Co-Mg the high-melting phase CoAl enters into equilibrium with the magnesium-rich solid solution. By contrast, only a phase derived from FeAl 3, and none of the more iron-rich aluminium-iron compounds, is found in equilibrium with zinc in the system Al-Fe-Zn. The main features of the equilibria are discussed in terms of the free energies of phases present, and the data, taken together with the results of previous work, lead to a better understanding of the factors affecting the formation of aluminium-rich ternary compounds.