Transmission Electron Microscope Study on Deformation and Fracture of Cementite in Cold-Rolled Steels

Abstract

In order to study the deformation behavior of cementite in carbon steels cold-rolled to various degrees of reduction, observations of dislocation structures were made by using a transmission electron microscope.The results obtained are summarized as follows:(4) The fracture of lamellar cementite proceeded in the following way: (a) The gliding of cementite crystals in the heterogeneous manner results in division of the original cementite crystal into several undeformed blocks. (b) The mutual gliding displacement between two adjacent blocks (height of slip steps) increases with a successive deformation of the cementite. (c) Finally, the cementite is completely broken away along the boundaries of the blocks probably due to the stress concentration at the slip steps.

Structure of several historic blades at nanoscale

“…This is in agreement with the finding of Keh [58], who identified (010) as the major slip and stacking fault plane of Cm. The same slip geometry has also been observed by Inoue et al [15]. They concluded that dislocation glide along (100), (010) and (001) was connected with plastic deformation of Cm.…”

Atom probe and transmission electron microscopy investigations of heavily drawn pearlitic steel wire

“…Electron microscopy studies by Maurer and Warrington, [5] Gil Sevillano, [6] and Inoue et al [7,8] established that cementite lamellae in pearlite deformed to somewhat lower strains contain numerous planar defects and slip bands. In this study, the drawing process reduces cementite lamellae to a thickness of about 2 to 5 nm and introduces numerous boundaries between the cementite nanocrystals.…”

“…The latter appear much like the stacking faults and slip traces seen in pearlitic cementite deformed to low strains. [5][6][7][8] These observations indicate that there is some internal strain in the as-transformed pearlite. Figure 2 shows cross-sectional TEM micrographs of a wire drawn to a true strain of 4.22.…”

“…Previous microstructural investigations have established a number of salient characteristics associated with the wire drawing process. [2,3,4] The strength of the wire increases exponentially with the drawing strain, and, despite the limited ductility of monolithic cementite crystals, [5][6][7][8] the cementite lamellae in pearlitic wire co-deform with ferrite. The ferritic component develops a strong ͗110͘ wire texture, [9] and the cementite lamellae appear to fragment into planar arrays of small particles.…”

Crystal Plasticity Analyses of Scale Dependent Mechanical Properties of Ferrite/Cementite Lamellar Structure Model in Pearlite Steel Wire with Bagaryatsky or Pitsch-Petch Orientation Relationship

“…1,2,4) These excellent mechanical properties are considered to come from strengthening of ductile ferrite layers 1,2) and at the same time some amount of stable plastic deformation of brittle cementite layers. 5,6) Dislocations needed for the plastic deformation of cementite layer are supplied from the ferrite layers 7) and the stable plastic deformation of cementite layer is realized when yield stress and strain hardening rate of the ferrite layers are increased. 8) Thickness of ferrite layer decreases with reduction of cross-section area of pearlite wire by drawing.…”