Pearlite

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

Eutectoid decomposition mechanisms in hypoeutectoid Ti-X alloys

Abstract: A TEM study has been made of the bainite reaction in five hypoeutectoid Ti-X alloys, where X was successively cobalt, chromium, copper, iron and nickel. Rational orientation relationships were demonstrated amongst eutectoid α, eutectoid intermetallic compound and the β matrix in Ti-Ni, Ti-Co and Ti-Cr. Formation of Ti2Co at α:β boundaries was observed. Eutectoid α in bainite was found to be slightly misoriented with respect to proeutectoid α, indicating that it is separately nucleated, perhaps sympathetically, rather than the result of the continued growth of proeutectoid α. Eutectoid Ti2Co and Ti2Cu crystals in bainite were approximately equiaxed whereas Ti-Cr2 crystals were elongated, a result ascribed to a ledge height-to-spacing ratio ν/λ at intermetallic compound crystal: β boundaries approaching that of eutectoid (α:β boundaries in Ti-Cr but not in the other two systems. In the Ti-Fe alloy, eutectoid α and eutectoid TiFe were directly observed to have ledged interphase boundaries with their β matrix, but with different inter-ledge spacings and growth directions. Observation of pearlite lamellae growing normal to the broad faces of proeutectoid α plates in the Ti-Ni alloy indicates that this mode of eutectoid decomposition, like that of bainite, can develop from partially coherent interphase boundaries. The suggestion was offered that pearlite forms when λ approachesh at the nucleating proeutectoid α:β interface and that bainite develops when λ h at this interface.

A mathematical model for the phase transitions in eutectoid carbon steel

Abstract: A mathematical model for the austenite-pearlite-martensite phase change in eutectoid carbon steel is presented. The model is based on Scheil's additivity rule and the Koistinen-Marburger formula. Existence and uniqueness results are established. To confirm the validity of the model, the Jominy end quench test has been simulated numerically for the carbon steels C 1080 and C 100 W1. The results are in good agreement with measurements

Effect of Destabilizing Heat Treatment on Solid-State Phase Transformation in High-Chromium Cast Irons

Abstract: This work describes the influence of secondary carbide precipitation at destabilizing heat treatment on kinetics of austenite phase transformation at a subcritical range of temperatures in high-Cr cast irons, alloyed with 4 to 6 wt pct of Mn or by complex Mn-Ni-Mo (Mn-Cu-Mo). The samples were soaked at 1073 K to 1373 K (800 °C to 1100 °C) (destabilization) or at 573 K to 973 K (300 °C to 700 °C) (subcritical treatment); the combination of destabilization and subcritical treatment was also used. The investigation was carried out with application of optical and electron microscopy and bulk hardness measurement. Time-temperature-transformation (TTT) curves of secondary carbide precipitation and pearlite transformation for as-cast austenite and destabilized austenite were built in this work. It was determined that the secondary carbide precipitation significantly inhibited the pearlite transformation rate at 823 K to 973 K (550 °C to 700 °C). The inhibition effect is more evident in cast irons alloyed with complex Mn-Ni-Mo or Mn-Cu-Mo. The possible reasons for transformation decelerating could be austenite chemical composition change (enriching by Ni, Si, and Cu, and depleting by Cr) and stresses induced by secondary carbide precipitation.