Transactions of Materials and Heat Treatment

Title：Diffusion phase transformation test of ultra high strength steel and its kinetic model

Authors： Zhang Qian Zeng Fanjing Jia Zhuohan Zhang Wentao Wu Dongsen Quan Guozheng

Unit： Chongqing University

KeyWords： steel BR1500HS diffusion phase transformation thermal expansion test kinetics model isothermal phase change

ClassificationCode：TG131

year,vol(issue):pagenumber：2018,43(8):178-183

Abstract：

The experiments of isothermal phase transformation for a series of steel BR1500HS round bar samples were conducted by thermal simulated test machine Gleeble 3500, and the thermal expansion curves of diffusion phase transformation were obtained. Combined with the observation results of sample microstructure, the species of diffusion phase were ascertained, and the time-temperature-transformation(TTT) curves of diffusion phase transformation of steel BR1500HS were drawn. Moreover, the TTT curves presente as ‘double C’ type, and the ‘nose temperatures’ are 480 and 640 ℃ respectively which exhibite the shortest incubation stage. In the end, the diffusion phase transformation kinetics model was established by introducing the Johnson-Avrami kinetics equation, which could predict the relationship between transformed volume fraction and time in the complete diffusion transformation temperature region of UHSS under any transition conditions. Thus, for transformation temperature, the transition velocity is fast at lower temperature, and for transformation stage, the transition velocity is fast at the middle stage. Finally, the specific quantitative relationship was given by the expressions in the model.

Funds：

重庆大学大学生科研训练计划项目(CQU-SRTP-2017166;CQU-SRTP-2017162;CQU-SRTP-2016132)

张谦（1998-），男，本科，E-mail：1137691086@qq.com；通讯作者：权国政（1980-），男，博士，副教授，E-mail：quangz3000@sina.com

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