No abstract

No abstract

No abstract

No abstract

The iron meteorite Santa Catharina (35 wt% Ni) is studied by transmission electron microscopy and Mössbauer spectroscopy in order to establish the equilibrium state for FeNi Invar alloys. Three magnetic phases are identified by Mössbauer spectroscopy; TEM reveals two co‐existing orientations of the parent γ phase. Annealing experiments on the meteorite at temperatures of 200 to 400 °C produce readjustments of the proportions and compositions of the magnetic phases and result in the disappearance of one of the parent γ‐orientations. The implications of these changes for the equilibrium state of FeNi Invar alloys are discussed in terms of the presence of a miscibility gap at low temperatures in addition to the FeNi ordering reaction. It is shown that a metastable equilibrium state is actually achieved in FeNi alloys with ≈︁ 30 to 40% Ni that comprises γ + ordered FeNi.