Equilibrium phases in the miscibility gap of the Fe-NiAl system in connection with the physical properties of the alloys.

A determination of the alpha(1) and alpha(2) phase compositions at low temp eratures in the miscibility gap of the Fe-NiAl partial system is presented. For this purpose, a study of this two-phase al and at region is carried ou t. The chemical compositions of the investigated alloys were selected along the NiAl-Fe line. This study is performed using physical property measurem ents: density, saturation magnetization and lattice parameter. The identifi cation of the phases and of the microstructural changes of these alloys wer e carried out by X-ray diffraction and transmission electron microscopy. Th e variations of physical properties related to alloy chemical composition w ere analyzed by means of models based on the law of mixtures. This analysis clearly reveals that alloys are constituted of two phases alpha(1) and alp ha(2) whose respective chemical compositions are constant, only the proport ions are variable. These two phases were characterized. The low temperature part of the Fe-NiAl vertical section can be considered as a quasi-binary s ystem. The two boundaries of the miscibility gap on the Fe-NiAl tie-line ar e thus accuratly determined.