Pearlite

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

Solution of the Diffusion Equation Applicable to the Edgewise Growth of Pearlite

Abstract: The diffusion equation is transformed to a set of coordinates moving with the pearlite interface and a solution applicable to the problem obtained in the form of an infinite series of terms. Using the first three terms, the edgewise velocity of pearlite growth is calculated for a plain carbon eutectoid steel using data most of which are obtained by extrapolation. The values obtained show reasonable agreement with values for the rate of pearlite nodule growth determined by Hull, Colton, and Mehl. The velocity increases with decreasing temperature, as expected, and it is shown that this is caused by the change in the solubilities of ferrite and cementite in austenite with temperature. The theory predicts curved ferrite‐austenite and cementite‐austenite interfaces and the carbon concentration in austenite is shown to vary across each of these interfaces.

Thermal conductivity of cast iron: Models and analysis of experiments

Abstract: Cast iron can be viewed as a composite material. We use effective medium and other theories for the overall conductivity of a composite, expressed in the conductivities, the volume fractions, and the morphology of the constituent phases, to model the thermal conductivity of grey and white cast iron and some iron alloys. The electronic and the vibrational contributions to the conductivities of the microconstituents (alloyed ferrite, cementite, pearlite, graphite) are discussed, with consideration of the various scattering mechanisms. Our model gives a good account of measured thermal conductivities at 300 K. It is easily extended to describe the thermal conductivity of other materials characterized by having several constituent phases of varying chemical composition.

Microstructural Features of Austenite Formation in C35 and C45 alloys

Abstract: The microstructural evolution during continuous heating experiments has been studied for two C-Mn steels with carbon contents in the range 0.35 to 0.45 wt pct using optical microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). It is shown that the formation of the austenitic phase is possible in pearlite as well as in ferrite regions. Thus, a considerable overlap in time of ferrite-to-austenite and pearlite-to-austenite transformations is likely to occur. Another observation that was made during the experiments is that, depending on the heating rate, the pearlite-to-austenite transformation can proceed in either one or two steps. At low heating rates (0.05 oC/s), ferrite and cementite plates transform simultaneously. At higher heating rates (20 oC/s), it is a two-step process: first ferrite within pearlite grains transforms to austenite and then the dissolution of the cementite lamellae takes place. Several types of growth morphologies were observed during the experiments. The formation of a finger-type austenite morphology was noticed only for low and intermediate heating rates (0.05 oC/s and 20 oC/s), but not for the heating rate of 300 oC/s. The formation of this fingertype austenite occurs on pearlite-ferrite grain boundaries and coincides with the direction of cementite plates. The carbon inhomogeneities in the microstructure affect the formation of martensitic/bainitic structures on cooling.