Directional Growth of Pearlite in Fe-C Eutectiod Alloys

摘要

The maximum temperature gradient which can be established in a 1/4 inch diameter eutectiod steel rod while maintaining a flat pearlite growth front perpendicular to the axis of the rod and not melting the surface of the sample has been determined to be approximately 2200 degrees C/cm. The experimental setup for these experiments provided such an efficient means of heating a sample that only a small fraction of the available power was required. The conditions for pearlite nucleation in a temperature gradient can be predicted from CCT data for gradients of 500, 1000, and 2000 degrees C/cm. At a gradient of 175 degrees C/cm, the conditions for nucleation can not be predicted from CCT data. The fact that ferrite nucleated ahead of the growth front, even at the slowest growth rate used, indicated that the system becomes more sensitive to composition and the nucleation of proeutectiod ferrite is more favorable than the nucleation of pearlite as predicted by CCT data. Although the results of the interlamellar spacing measurements wer inconclusive, there does appear to be a stress effect. The trend in the average spacings is towards increased spacing with increased tensile stress. (ERA citation 09:016885)