An X-ray analysis of the nickel-aluminium system

Abstract

An X-ray analysis of the nickel-aluminium system has been made. A comprehensive series of powder photographs were taken of slowly cooled alloys, and in addition some quenching experiments were made on the nickel-rich alloys. In several important particulars the results differ from the phase-equilibrium diagram published by Gwyer (1908) (fig. 1 a ). This diagram has therefore been modified in the direction indicated by our work (fig. 1 b ). The solid solution of aluminium in nickel shown by Gwyer has been found to contain a miscibility gap at room temperatures. The α -phase, which is a face-centred cubic solid solution of aluminium in nickel, extends to 89 atomic % of nickel at room temperatures. The α' -phase, which is a facecentred cubic solid solution closely corresponding to the composition Ni 3 Al, has a superlattice (Westgren and Ekman 1930), nickel atoms occupying centres of cube faces and aluminium atoms cube corners. Quenching extends the range of the α -phase until in alloys quenched from 1100° there is no break between the α and α' structures.