Pearlite

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

The influence of thermomechanical treatment on the transformation behaviour of steels

Abstract: The effect of thermomechanical treatment on the γ – α-transformation in steel has been reviewed. It has been shown that the thermo-mechanically conditioned austenite significantly influences the kinetics of transformation due to the differences in the formation of product phases. An enhanced nucleation during the diffusion controlled transformation, as a result of austenite grain refinement and/or austenite strengthening, leads to a substantial refinement of the microstructure (ferrite grains, pearlite nodules). The deformation substructure of austenite may strongly affect the shear mechanism of the diffusionless transformation, which leads to finely fragmented martensite crystals. Such differences in the transformation characteristics result in different formation temperatures of transformation products and so to the changes in CCT diagrams.

Microstructure and texture evolution in fully pearlitic steel during wire drawing

Abstract: The evolution of morphology of pearlite and crystallographic texture of ferrite matrix in fully pearlitic steels during wire drawing were quantitatively investigated. The study revealed that a fiber structure of the pearlite morphology and a fiber texture of the ferrite matrix begin to take shape and develop gradually with increasing strain. The growth rates of the fiber structure and the texture are different in different regions within the wires with increasing drawing strain. There is a close relationship between the pearlite morphology and the crystalline texture during wire drawing. The pearlite interlamellar spacing (ILS) and thickness of cementite lamellae (Tθ) decrease gradually both in longitudinal and transverse sections. The definition of pearlite colony should be reconsidered for describing microstructure of the wire drawing deformed pearlitic steels.

Al as solid solution hardener in steels

Abstract: Aluminium in solution in the ferrite in ferrite/pearlite steels has been found to have little influence on strength of the ferrite probably because up-till recently it has been added in very small amounts (0˙02–0˙08 wt-%Al) as a grain refining addition. There is indeed some doubt in the literature as to whether Al can solid solution harden. This lack of knowledge has not been important while Al additions are small but recently Al has been added in much greater amounts 0˙5–2% in some new grades of transformation induced plasticity (TRIP) steels. These steels have often an essentially ferritic structure with retained austenite and bainitic ferrite. The main thrust of the paper has therefore been to determine the solid solution hardening effect of Al in ferritic structures. Steels with varying Al levels from 0˙02 to ∼2% at two C levels, 0˙02 and 0˙1% were tensile tested after hot rolling so as to determine the solid solution hardening effect of Al. It was found in the 0˙1%C steel that some of the pea...

Effect of step quenching on microstructures and mechanical properties of HSLA steel

Abstract: Step quenching and tempering (SQT) for HSLA multi-phases steel was designed to obtain the desirable multi-phases microstructure with the superior mechanical properties. Quenching and tempering (QT) and intercritical quenching and tempering (IQT) was also conducted as controls. Besides, Effects of austenitizing temperature for the different treatment routes on microstructural characteristics and mechanical properties were also investigated. Due to the cooperation of the “soft” ferrite/pearlite and “hard” martensite, the samples undergoing SQT possess the relatively high tensile strength and impact toughness, and the lowest yield ratio. Increase of austenitizing temperature results in the coarse austenite grains, and thus significantly decrease of tensile strength and impact energy, in spite of the heat treatment paths. Higher austenitizing temperature also leads to lower density of dislocations and higher grain size, which reduces the yield ratio for all samples.

Study of dislocation cell structures from uniaxial deformation of AISI 4340 steel

Abstract: A considerable interest has focused on the role of substructure during the uniaxial deformation of pure metals and alloys. To elucidate this role further, the evolution of dislocation cell structures during the tensile straining of AISI 4340 steel was investigated by transmission electron microscopy. It was found that substructural evolution reflects the inhomogeneous distribution of stress and strain in a composite material consisting of ferrite and pearlite. Cell formation occurs at different stages in the phases, with a more advanced state of cell development in ferrite grains indicating higher dislocation mobility. The strength of 4340 steel appears to be largely due to the pearlite. Work hardening by cell mechanisms occurs in the ferrite only after stresses exceed the pearlite strength. The dependence of dislocation cell size on flow stress σ was also studied and σ is found to be linearly related to the inverse cell size, indicating the operation of similitude in the “meshlength” theory of work hardening over most of the strain range. The breakdown of this relationship at higher strains is related to the transition to stage IV hardening behaviour, where increased dislocation mobility through profuse cross slip results in a very low hardening rate and nearly constant cell size.