Effect of isothermal cooling time on microstructure transformation and hardness of a Ti-V-Mo microalloyed steel

doi:10.13251/j.issn.0254-6051.2021.06.020

Abstract

Abstract: Effect of isothermal cooling time on microstructure transformation, precipitation behavior and hardness of a Ti-V-Mo microalloyed steel was investigated by means of OM, SEM, TEM and Vickers hardness tester, and the factors influencing the hardness change were discussed. The results reveal that when the Ti-V-Mo microalloyed steel after austenitization is isothermally cooled at 630 ℃ from 0 to 3 h, with the increase of isothermal time, the proportion of ferrite in the matrix increases while the proportion of martensite and bainite decreases. In addition, the hardness increases firstly and then becomes stable, then re-increases and finally declines slightly. At the isothermal time ranging from 60 s to 1200 s, the hardness plateau occurs because the precipitation strengthening effect of (Ti, V, Mo)C nano-particles can compensate for the hardness loss caused by matrix softening due to phase transformation. When the isothermal time is 3600 s, the maximum hardness is 457 HV, and the precipitation strengthening effect of (Ti, V, Mo)C nano-particles is the best.

Key words: Ti-V-Mo microalloyed steel, precipitation strengthening, ferrite, isothermal cooling time, hardness

CLC Number:

TG142.1

Yu Yinjun, Zhao Shiyu, Zhang Ke, Li Zhaodong, Chen Zihao, Zhang Qing, Wang Xinzhi, Qian Jianqing. Effect of isothermal cooling time on microstructure transformation and hardness of a Ti-V-Mo microalloyed steel[J]. Heat Treatment of Metals, 2021, 46(6): 95-101.

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