The ferrite and austenite lattice parameters of Fe–Co and Fe–Cu binary alloys as a function of temperature

Abstract

The lattice parameters of Fe–1% Cu, Fe–2% Cu, Fe–1% Co, and Fe–2% Co binary alloys were determined by means of neutron diffraction at temperatures around the austenite–ferrite phase transformation (860–1350 K). While the thermal expansion coefficients prove to be similar to those of Fe for all alloys, Cu and Co have an opposite effect on the lattice parameter of Fe. Addition of Cu increases the lattice parameter in both ferrite ( α) and austenite ( γ), while Co decreases the lattice parameter. For all alloys, the α↔ γ phase transformation introduces a volume change of 1.0%. Evidence is found that both ferrite and austenite are slightly strained ( ε<8×10 −4) when both phases are present simultaneously.