Crystallization of amorphous Fe- P- C alloys

The transformation of amorphous Fe-P-C alloys from the amorphous state to crystalline state was studied by differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and transmission electron microscopy (TEM). Compositions included iron and phosphorus rich alloys and alloys with compositions near the eutectic composition. The crystallization of Fe-P-C alloys proceeded by the following processes: for the iron rich alloy, bcc α Fe precipitated first; for the phosphorus rich alloy, Fe₂P and iron carbide precipitated first; for the alloys near the eutectic line, the eutectic reactions dominated, although some α Fe or Fe₂P plus iron carbide crystals were observed. The composition dependence of the transformation can be explained successfully by a free energy model with the help of the phase diagram. From DSC and TEM results, the nucleation rate of the α Fe precipitate decreased with time in the Fe rich alloys according to the recrystallization theory of Avrami. Formerly Research Fellow in the Department of Metallurgy and Materials Science, University of Pennsylvania This paper is based on a presentation made at a symposium on “Recovery Recrystallization and Grain Growth in Materials” held at the Chicago meeting of The Metallurgical Society of AIME, October 1977, under the sponsorship of the Physical Metallurgy Committee.