A New Reversible Solid-State Transformation in Iron–Nickel Alloys in the Invar Range of Compositions

Abstract

UNUSUAL physical properties exhibited by alloys of the iron–nickel system in various ranges of composition have led to extensive investigations¹ of this system in the past. One group of alloys is that contained in the invar range, namely, 30–45 atom per cent nickel, and is characterized by unusual thermal expansion, magnetic and other physical properties. In spite of extensive investigations, the general sluggishness of solid-state transformations in the iron–nickel system has prevented true equilibria from being well established. The properties of these alloys, therefore, have remained largely unrelated to their structural and/or crystallographic features.