Pearlite

About: Pearlite is a research topic. Over the lifetime, 6028 publications have been published within this topic receiving 65695 citations.

An assessment of the additivity principle in predicting continuous-cooling austenite-to-pearlite transformation kinetics using isothermal transformation data

Abstract: The limits of applicability of the Additivity Principle, necessary for the prediction of continuous-cooling transformation kinetics from isothermal transformation data, are clarified based on an analysis of recently measured austenite-to-pearlite transformation kinetics in a eutectoid, plain-carbon steel. It has been found that additivity holds for the transformation event, exclusive of the incubation period, in this steel. But the isokinetic condition defined by Avrami, and the early site-saturation criteria postulated by Cahn as sufficient conditions for additivity are not satisfied. Thus a new condition, termed “effective site saturation”, is proposed in which the growth of pearlite nucleated early in the transformation dominates the overall kinetics of austenite decomposition. A criterion for effective site saturation has been established.

Investigation of orientation gradients in pearlite in hypoeutectoid steel by use of orientation imaging microscopy

Abstract: For steels and related ferrous alloys containing pearlite, the precise microstructural characterization of pearlite is of great importance since it significantly contributes to the mechanical properties of the material. The yield strength of pearlite depends on its interlamellar spacing. Refining that spacing entails an increase in strength which follows a HallPetch type relation [1,2]. Beyond the contribution of the interlamellar spacing, the strength of pearlite was reported to depend as well on the prior austenite grain size and on the pearlite colony size although these effects were considered to be small [3]. In contrast to these findings Ray and Mondal [4] observed that the strength of pearlite in hypoeutectoid steels does not follow a Hall-Petch type relation. They reported that the strength of pearlite in the hypoeutectoid steels varied considerably even when the interlamellar spacings in the pearlite colonies are almost constant. They attributed that variation in the strength of the pearlite in the hypoeutectoid steels to the influence of hydrostatic stresses exerted by the presence of proeutectoid ferrite in the material. Besides the morphological parameters such as interlamellar spacing, prior austenite grain size, and pearlite colony size, other microstructural factors such as the amount of elements in solid solution and the dislocation density in the ferrite have been commonly taken into account when evaluating the strength of pearlite. The influence of the substructure and of the crystallographic texture of the pearlite, however, have not been sufficiently considered in that context yet. The contributions of these influencing factors were up to now only evaluated on the basis of regression analysis by which possible scattering of the strength of the pearlite constituents due to the presence of microstructural heterogeneities was simply averaged over the whole pearlite volume rather than studied in detail. It is a common observation though that the lamellar structure in a pearlite colony is not always homogeneous, but rather contains various types of substructures even in the astransformed state. Puttick [5] has identified several kinds of growth faults in the lamellae of the pearlite colonies. These include linear discontinuities in the cementite lamellae; branched crystallization; deviations of lamellar orientation; rod-like growth; and growth of round cementite inclusions. Bramfitt and Marder [6] have also studied the substructural faults of pearlite colonies. They showed that areas with higher dislocation densities and extended dislocation substructures in the pearlitic ferrite were sometimes associated Investigation of Orientation Gradients in Pearlite in Hypoeutectoid Steel by use of Orientation Imaging Microscopy