In Situ Neutron Diffraction Study of Phase Transformation of High Mn Steel with Different Carbon Content

• Main Authors: Youngsu Kim, Wookjin Choi, Hahn Choo, Ke An, Ho-Suk Choi, Soo Yeol Lee
• Format: Article
• Language: English
• Published: MDPI AG 2020-02-01
• Series: Crystals
• Subjects: high mn steel; phase transformation; carbon; stacking fault energy; neutron diffraction
• Online Access: https://www.mdpi.com/2073-4352/10/2/101

In situ neutron diffraction was employed to examine the phase transformation behavior of high-Mn steels with different carbon contents (0.1, 0.3, and 0.5 wt.%C). With increasing carbon contents from 0.1 C to 0.5 C, the austenite phase fraction among the constituent phases increased from ~66% to ~98%, and stacking fault energy (SFE) increased from ~0.65 to ~16.5 mJ/m². The 0.1 C and 0.3 C steels underwent phase transformation from &#947;-austenite to &#949;-martensite or &#945;&#8217;-martensite during tensile deformation. On the other hand, the 0.5 C steel underwent phase transformation only from &#947;-austenite to &#949;-martensite. The 0.3 C steel exhibited a low yield strength, a high strain hardening rate, and the smallest elongation. The high strain hardening of the 0.3 C alloy was due to a rapid phase transformation rate from &#947;-austenite to &#949;-martensite. The austenite of 0.5 C steel was strengthened by mechanical twinning during loading process, and the twinning-induced plasticity (TWIP) effect resulted in a large ductility. The 0.5 wt.% carbon addition stabilized the austenite phase by delaying the onset of the <i>&#949;</i>-martensite phase transformation.