Abstract:In the organic light-emitting diode display industry, Invar exhibits anomalously low thermal expansivity and is, therefore, used as a material for fine metal masks, which are necessary components for the evaporation process of diode materials. We present an electroforming method for fabricating Fe-Ni alloys with a coefficient of thermal expansion lower than that of conventional Invar. The principle of controlling the thermal expansivity of electroformed Fe-Ni alloys is clarified in terms of the behavior of the phases constituting them. The cause of the Invar anomalies, which has not yet been fully elucidated, is explained by combining the Weiss model based on the electron configurations of Fe atoms and a model that we propose based on atom configurations.