ELECTRON MICROSCOPY AND DIFFRACTION STUDY OF THE CARBIDE PRECIPITATED AT THE FIRST STAGE OF TEMPERING OF MARTENSITIC MEDIUM CARBON STEEL.

Abstract

The crystal structure and precipitation mode of the carbide in a martensitic 0. 45%C (2. 06 at. %) steel tempered 1 to 40 days at 120 C and 1 to 3 hr at 200 C were investigated. In both platelike and lath martensite, the precipitated carbide was the eta Fe//2C previously found in high carbon (1. 13%) steel. Crystal morphology and the orientation relationships between carbide and matrix were also the same. In general, precipitation occurred along dislocations, but grain boundary precipitation was also observed in the nonparallel lath region.