Lattice constant of iron and austenite including its supersaturation phase of carbon

Electrolytic iron powder was heated into gamma-iron phase and carburized in austenite and its supersaturation phase under the gas mixture of CO and CO, with carbon activity of 0.1 to 1.0. The spacing of lattice planes of iron was measured using a high temperature X-ray diffractometry (XRD), which gradually increased with time and arrived at a constant value. The carbon concentration in samples after experiment was measured by a combustion-infrared absorptiometry. The lattice constants, a(0) (nm), of alpha-iron, gamma-iron and austenite including its supersaturation phase of carbon have been determined as follows; (alpha-iron: a(0)=1.602X10(-9)T(2)+2.059X10(-6)T+0.2860 (295to1183K) gamma-iron: a(0)=8.1593X10(-6)T+0.35519 (1183 to 1550K) Austenite: a(0)=0.35519+8.1593X 10(-6)T+1.7341 X 10(-3)C (0 to 3.35 masss% and 1452 to 1 550 K) where T and Care temperature (K) and carbon concentration (mass%), respectively.