EFFECT OF NITROGEN ON MARTENSITIC TRANSFORMATION AND MECHANICAL PROPERTIES OF TWIP STEEL
HUANG Baoxu1, 2), WANG Changzheng1), WANG Xiaodong3), RONG Yonghua3)
1) School of Materials Science and Engineering, Research Institute of Non--ferrous Metals, Liaocheng University, Liaocheng 252059
2) State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000
3) School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200240
Cite this article:
HUANG Baoxu WANG Changzheng WANG Xiaodong RONG Yonghua. EFFECT OF NITROGEN ON MARTENSITIC TRANSFORMATION AND MECHANICAL PROPERTIES OF TWIP STEEL. Acta Metall Sin, 2012, 48(7): 769-774.
Abstract Twinning induced plasticity (TWIP) steels show large elongation and high tensile strength,
exhibiting a super balance between strength and plasticity. Until now, the effects of Mn, Si and Al on stacking
fault energy (SFE) and phase transformation of TWIP steel had been investigated, but the effect of N on phase
transformation, especially martensitc transformation in TWIP steel has not been reported. In the present paper, the
mechanical properties of TWIP steel with the addition of N were tested. The phases were analyzed by XRD and
the microstructure was characterized by TEM. The average and local probabilities of stacking faults were also
calculated by using shifts of X-ray peak and electron diffraction spot, respectively. Compared with the
conventional TWIP steel, the results showed that at a lower SFE level, when fcc austensite or hcp martensite
transformed to bcc martensite, the largest interstice decreased from 0.1047 to 0.0725 nm. The lattice distortion
energy of bcc martensite was greatly enlarged by N, which situated in the interstices, leading to the suppression of the bcc martensitic transformation. As a result, the content of hcp martensite increased, causing the increase of
strength and decrease of plasticity. Besides, the results also showed that deformation increased stacking faults and
hcp or bcc martensitic transformation consumed a large number of stacking faults.
