Chemical driving force,shear moduli of ferrite and metastable austenite,and strain energy for γ→α transformation in pure iron

The chemical driving force/unit volume ∆G_v for the γ→α.transformation. in pure iron is computed as a function of undercooling. Similarly, the strain δ accompanying the transformation at different temperatures is also calculated from lattice parameter measurements. Shear moduli μ_α of ferrite and metastable austenite μ_γ are derived from various sources. At temperatures down to the Curie temperature (768°C), μ_α and μ_γ are very similar, and enable the strain energy/unit volume W to be calculated from the expression W=2 (μ_α+ μ_γ)δ². The data give the metastable equilibrium temperature T;′₀ for the massive ferrite transformation as 1156 K. The distinction between equiaxed ferrite, massive ferrite, and Widmanstätten ferrite is discussed.

MST/3138