2(a) and 2(b) show a bright-field TEM image of twinned martensite and corresponding selected area electron diffraction (SAED) pattern along α-Fe zone axis (ZA), respectively. 2 presents further TEM observations of twinned martensite structure, as shown in Fig. 1(d) exhibits an obvious twin contrast compared to Fig. By tilting the specimen, different diffraction contrasts of the martensite have been obtained, as shown in Figs. 1(c) shows the bright-field TEM image of individual martensite structure without twin contrast. 16–18 Due to the diffraction conditions, the twin contrast of some martensite in Fig. In high carbon steel, twins represent a common substructure in martensite. The martensite phase exhibits a plate-like morphology, whereas the retained austenite can be identified from the dislocation contrast close to the martensite. 1(b) shows a bright-field TEM image of the quenched specimen, which also confirmed the presence of two phases, martensite and retained austenite. 1(a) shows the XRD pattern of the quenched specimen, which indicates that martensite and retained austenite are the primary constituents of the specimen. 1 presents the crystallography and morphology of a water-quenched Fe-1.4C specimen, austenitized at 950 ☌ for 30 min. 11,12,22–25 During tempering, the ω-Fe phase could transform into θ-Fe 3C cementite. 22–25 In carbon steels, carbon atoms occupy the octahedral interstitial sites in ω-Fe phase and stabilize fine particle-like ω-Fe phase. 19,20 Moreover, cementite is usually aligned along the α-Fe directions on the ⟨111⟩-type body-centered cubic (bcc) twin boundaries in a twinned martensite structure. Most of the carbides prefer to nucleate and precipitate on twinning planes instead of other kinds of boundaries or dislocations in tempered carbon steels. 16–18 Earlier transmission electron microscopy (TEM) observations have revealed that carbides are significantly influenced by the presence of fine twins. In high carbon steels, twins are usually observed as the substructure of martensite. The current study provides a baseline to understand the microstructural evolution in high carbon steels during heat treatment processes. Furthermore, the orientation relationships between θ-Fe 3C cementite and α-Fe are indexed as: θ// α-Fe, θ// α-Fe, θ// α-Fe and θ// α-Fe, which are related to the transformation of ω-Fe to θ-Fe 3C cementite. The TEM and electron diffraction analysis reveals that diffraction spots of θ-Fe 3C cementite phase are located at 1/6, 2/6, 3/6, 4/6 and 5/6 (22 2 ¯) α-Fe and (2 1 ¯ 1) α-Fe along α-Fe and α-Fe ZAs. Moreover, martensite decomposes into a lamellar structure and ω-Fe(C) phase transforms into θ-Fe 3C cementite during tempering. When specimens are in-situ heated in TEM, few additional diffraction spots are observed at 1/6, 3/6 and 5/6 (2 1 ¯ 1) α-Fe positions along the α-Fe ZA. In quenched specimens, the ω-Fe(C) phase is a common substructure in twinned martensite and its diffraction spots are located at 1/3 and 2/3 (2 1 ¯ 1) α-Fe positions along the α-Fe zone axis (ZA). In the present study, transmission electron microscopy (TEM) and selected area electron diffraction (SAED) are used to examine the microstructural evolution in quenched and tempered high carbon steels. You can browse and sort reflexions in the list double-click any reflexion to instantly locate it in the plot.Quenching and tempering are mostly employed to tune the mechanical properties of the high-carbon steels. Search, Browse ReflexionsĪn integrated Search field lets you quickly find simulated reflexions: in the plotted pattern, or in the Reflexions List. ![]() Patterns can be sorted according to various criteria and auto-stacked on screen. You can also specify a precise plot range, use the Scroller tool or use the toolbar's scale and scrolling commands. Just "pinch-to-zoom", and slide to scroll horizontally, or scale vertically. Scaling and scrolling your diffraction pattern is a breeze with CrystalDiffract's trackpad support. You have extensive control over the display, including pattern colours, line and marker sizes/styles, transparency, shadows, peak overlays, gridlines, film styles and colours, peak labels (including content, positioning and alignment), Legend display, plot title - plus your text fonts and sizes. The Loupe gives a high-resolution view of yourĭata, without the need to keep changing scale.
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