抄録
Crystal structure and precipitation mode of the carbide in a martensitic 0.45 wt%C steel tempered at 120 and 200°C have been studied by means of electron microscopy and selected area diffraction. In both plate-like and lath martensites, the precipitated carbide is η-Fe2C like the previous case of high carbon steel (Acta Met., 20 (1972), 645). The crystal morphology and the orientation relationships between the carbide and the matrix are also the same. In general, the precipitation occurs along dislocations, but it has been found that grain boundary precipitation also takes place in the non-parallel lath region and that in fine grains in this region the carbide precipitation does not occur. Some discussions are given to the crystal structure and the precipitation mode of the carbide.
