![]() ![]() ![]() Cohen, “ Microstructural changes on tempering iron-carbon alloys,” Transactions of the ASM 46, 851– 877 (1954). Krauss, Steels: Processing, Structure, and Performance ( ASM International, 2005). In general, heat treatments, such as tempering or aging, are carried out to obtain a desirable combination of strength and toughness. Quenched high carbon steel renders excellent strength but suffers from high brittleness. 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. Quenching and tempering are mostly employed to tune the mechanical properties of the high-carbon steels. ![]()
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