Defect lattices in some ternary alloys

Abstract In the work on ternary alloys with which the authors have been associated (Bradley, Goldschmidt, Lipson and Taylor 1937), the most outstanding feature has been the large range of composition over which the β (body-centred cubic) structure exists. This was not unexpected in the system Fe-Ni-Al (Bradley and Taylor 1938), where FeAl and NiAl both have this structure and thus may be expected to be isomorphous; but CuAl has quite a different structure, and it was therefore surprising to find the β phase-fields extending towards this composition in the systems Cu-Ni-Al (Bradley and Lipson 1938) and Fe-Cu-Al (Bradley and Goldschmidt 1939). These extensive phase-fields provide an opportunity for a more detailed examination of the phenomenon of the occurrence of defect lattices which takes place in the Ni-Al system (Bradley and Taylor 1937). In the β phase-field of this system a maximum occurs in the lattice-spacing curve almost exactly at the composition NiAl, the reduced spacing with the addition of aluminium being associated with the omission of nickel atoms from the lattice points. The present paper is an account of an investigation into the effect on this phenomenon of the addition of iron and copper.