Precipitation Behavior and Microstructural Evolution of Ferritic Ti–V–Mo Complex Microalloyed Steel
Precipitation behavior of (Ti, V, Mo)C and microstructural evolution of the ferritic Ti–V–Mo complex microalloyed steel were investigated through changing coiling temperature (CT). It is demonstrated that the strength of the Ti–V–Mo microalloyed steel can be ascribed to the combination of grain refinement hardening and precipitation hardening. The variation of hardness (from 318 to 415 HV, then to 327 HV) with CT (from 500 to 600–625 °C, then to 700 °C) was attributed to the changes of volume fraction and particle size of (Ti, V, Mo)C precipitates. The optimum CT was considered as 600–625 °C, at which the maximum hardness value (415 HV) can be obtained. It was found that the atomic ratios of Ti, V and Mo in (Ti, V, Mo)C carbides were changed as the CT increased. The precipitates with the size of < 10 nm were the V-rich particles at higher CT of 600 and 650 °C, while the Ti-rich particles were observed at lower CT of 500 and 550 °C. Theoretical calculations indicated that the maximum nucleation rate of (Ti, V, Mo)C in ferrite matrix occurred around 630 °C, which was consistent with the 625 °C obtained from experiment results.
KeywordsNano-sized precipitates Precipitation hardening Ti–V–Mo Coiling temperature Ferrite
This work was supported financially by the National Key Research and Development Program of China (Nos. 2017YFB0305100 and 2017YFB0304700), the National Natural Science Foundation of China (Nos. 51704008 and 51674004), the National Key Basic Research Program of China (No. 2015CB654803), the Science and Technology Foundation of China Iron & Steel Research Institute Group (No. 15G60530A) and the National Science Foundation of Anhui University of Technology (No. QZ201603). We are grateful to the Central Laboratory of Central Iron and Steel Research Institute, for HRTEM observation.
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