Pearlite

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

Achieving a desirable combination of mechanical properties in HSLA steel through step quenching

Abstract: Step quenching and tempering (SQT) treatment was applied on HSLA steels to achieve a multi-phase microstructure with a superior deformation performance. Intercritical quenching and tempering (IQT) as well as direct quenching and tempering (DQT) were also processed for comparison. Moreover, effects of intercritical temperatures before quench for different treatment methods on microstructure evolution and mechanical property were also investigated. Compared with IQT and DQT, SQT treatment produces a fine microstructure composited of soft ferrite/pearlite and hard martensite, with precipitates distributed along boundaries to maintain a large quantity of dislocations on deformation. Experiments involving tension and impact tests show that SQT samples with such multi-phase microstructure exhibit a desirable combination of mechanical properties. With increasing the intercritical temperature, the phase fraction of martensite is increased, which improves the strength but weakens the impact toughness in regardless of heat treatment type. Meanwhile, the yield ratio (YR) is found to be increased by higher intercritical temperature in all samples, due to the larger phase fraction of martensite with a large dislocation density and a finer grain structure. Such scenario is elucidated by using a model proposed through Swift's equation. That indicates that the content of multi-phase microstructure can be efficiently controlled via adjusting the intercritical temperature using SQT, which enables the optimization of phase composition according to the requirements of actual productions in engineering.

Kinetics of Reverse Transformation from Pearlite to Austenite in an Fe-0.6 Mass pct C Alloy and the Effects of Alloying Elements

Abstract: Substitutional alloying effects on reversion kinetics from pearlite structure at 1073 K (800 °C) in an Fe-0.6 mass pct C binary alloy and Fe-0.6C-1 or 2 mass pct M (M = Mn, Si, Cr) ternary alloys were studied. Reverse transformation in the Fe-0.6C binary alloy at 1073 K (800 °C) was finished after holding for approximately 5.5 seconds. The reversion kinetics was accelerated slightly by the addition of Mn but retarded by the addition of Si or Cr. The difference of acceleration effects by the addition of the 1 and 2 mass pct Mn is small, whereas the retardation effect becomes more significant by increasing the amount of addition of Si or Cr. It is clarified from the thermodynamic viewpoint of carbon diffusion that austenite can grow without partitioning of Mn or Si in the Mn- or Si-added alloys. On the one hand, austenite growth is controlled by the carbon diffusion, whereas the addition of them affects carbon activity gradient, resulting in changes in reversion kinetics. On the other hand, thermodynamic calculation implies that the long-range diffusion of Cr is necessary for austenite growth in the Cr-added alloys. It is proposed that austenite growth from pearlite in the Cr-added alloys is controlled by the diffusion of Cr along austenite/pearlite interface.