Effect of the Microsegregation on Martensitic and Bainitic Reactions in a High Carbon-High Silicon Cast Steel

摘要: Casting processes show some weaknesses. A particular problem is presented when the workpiece needs to be subjected heat treatments achieve a desired microstructure. This arises from microsegregation phenomena typically present in cast parts. The effect of on martensitic and bainitic transformations has been investigated high carbon-high silicon steel, with approximate composition Fe-0.8C-2Si-1Mn-1Cr (in wt. %), which was poured into 25 mm keel block-shaped sand molds. maps Cr, Si, Mn characterized by electron probe microanalysis (EPMA) that interdendritic regions are enriched while dendrites impoverished these elements, implying their partition coefficients lower unity (k < 1). As-quenched austempered microstructures (at 230 °C) were obtained analyzed after applying an austenitization treatment at 920 °C (holding for 60 min). thermal etching method used reveal prior austenite grain size showed bimodal distribution, larger grains dendritic (≈22.4 µm) than ones (≈6.4 µm). likely due both presence small undissolved cementite precipitates. Electron Backscatter Diffraction (EBSD) analysis carried out microstructure do not unveil any differences misorientation distribution frequency block between zones related bimodality size. On contrary, transformation starts earlier (incubation time 80 min), proceeds faster ferrite plates longer zones, impoverish solute. pattern leads non-uniform development reaction parts, modifying its kinetics resulting microstructures, would probably have major impact mechanical properties.