Research on the Microstructures and Mechanical Properties of Bainite/Martensite Rail Treated by the Controlled-Cooling Process

Jiajia Qiu; Min Zhang; Zhunli Tan; Guhui Gao; Bingzhe Bai

doi:10.3390/ma12193061

Research on the Microstructures and Mechanical Properties of Bainite/Martensite Rail Treated by the Controlled-Cooling Process

Materials (Basel). 2019 Sep 20;12(19):3061. doi: 10.3390/ma12193061.

Authors

Jiajia Qiu¹, Min Zhang², Zhunli Tan³, Guhui Gao⁴, Bingzhe Bai^{5

6}

Affiliations

¹ School of Mechanical, Electronic and Control Engineering, Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044, China. 17121353@bjtu.edu.cn.
² School of Mechanical, Electronic and Control Engineering, Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044, China. zhangm@bjtu.edu.cn.
³ School of Mechanical, Electronic and Control Engineering, Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044, China. tzli@bjtu.edu.cn.
⁴ School of Mechanical, Electronic and Control Engineering, Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044, China. gaogh@bjtu.edu.cn.
⁵ School of Mechanical, Electronic and Control Engineering, Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044, China. bzbai@bjtu.edu.cn.
⁶ Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China. bzbai@bjtu.edu.cn.

Abstract

A bainite/martensite multiphase rail is treated by the controlled-cooling process with different finish-cooling temperatures. The simulated temperature-time curves of the position of 5 mm and 15 mm below the rail tread (P5 and P15) express different trends. P5 has greater impact toughness and lower tensile strength than P15. Microstructural characterization was carried out by conducting scanning electron microscopy, X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. The greater tensile strength is due to the dispersed ε-carbides hindering the movement of dislocations. The greater impact toughness is attributed to the filmy retained austenite and the smaller effective grain with high-angle boundary. Finite element modeling (FEM) and microstructural characterization reasonably explain the changes of mechanical properties. The present work provides experimental and theoretical guidance for the development of rail with excellent mechanical properties.

Keywords: bainite/martensite multiphase rail; controlled-cooling process; crack initiation; decomposed martensite; high-angle boundary.

Abstract

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