Study on Bainitic Transformation by Dilatometer and In Situ LSCM

Xiaoyan Long; Fucheng Zhang; Zhinan Yang; Ming Zhang

doi:10.3390/ma12091534

Study on Bainitic Transformation by Dilatometer and In Situ LSCM

Materials (Basel). 2019 May 10;12(9):1534. doi: 10.3390/ma12091534.

Authors

Xiaoyan Long^{1

2}, Fucheng Zhang^{3

4}, Zhinan Yang^{5

6}, Ming Zhang⁷

Affiliations

¹ State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China. longxiaoyanlxy@163.com.
² Key Laboratory of Mechanical Reliability for Heavy Equipments and Large Structures of Hebei Province, Yanshan University, Qinhuangdao 066004, China. longxiaoyanlxy@163.com.
³ State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China. zfc@ysu.edu.cn.
⁴ National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao 066004, China. zfc@ysu.edu.cn.
⁵ National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao 066004, China. zhinanyang@ysu.edu.cn.
⁶ State Key Laboratory of Aviation Precision Bearings, Luoyang 471039, China. zhinanyang@ysu.edu.cn.
⁷ State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China. zhm@ysu.edu.cn.

Abstract

This study investigates the bainitic transformation kinetics of carbide-free bainitic steel with Si + Al and carbide-bearing bainitic steel without Si + Al, as well as the phase transformation and microstructure through in situ high-temperature laser scanning confocal microscopy. Results show that bainitic ferrite plates preferentially nucleate at the grain boundary. New plates nucleate on previously formed ones, including two dimensions which appear on a plane where a three-dimensional space of bainitic ferrite forms. Nucleation on the formed bainitic ferrite is faster than that at the grain boundary in some grains. The bainitic ferrite growth at the austenite grain boundary is longer and has a faster transformation rate. The bainitic ferrite growth on the formed bainitic ferrite plate is shorter and has a slower transformation rate. The location and number of nucleation sites influence the thickness of the bainitic ferrite. The higher the number of plates preferentially nucleating at the original austenite grain boundary, the greater the thickness of the bainitic ferrite.

Keywords: bainite; in situ LSCM; kinetics; microstructure; phase transformation.