The β Iron Controversy Revisited

Abstract

Early twentieth century Fe–C phase diagrams designated the paramagnetic BCC iron phase (ferrite) as β iron. By the third decade of the last century this designation all but disappeared from the literature. Why was this? Should the β phase of iron be brought back to phase diagrams? What effects on the phase diagram would arise if we differentiate the ferromagnetic magnetic phase (α) from the paramagnetic phase (β)? In this paper I will discuss some of the history of this β iron controversy and discuss the effects on the Fe–C binary phase diagram. I will urge that β iron should be returned to iron phase diagrams so as to better represent a proper view of magnetic phase equilibria, magnetic symmetry and magnetic phase transformations.