Transition from the twinning induced plasticity to the γ-ε transformation induced plasticity in a high manganese steel

Q. Xie, Z. Pei, J. Liang, D. Yu, Z. Zhao, P. Yang, R. Li, M. Eisenbach, K. An

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

Neutron-diffraction investigation on the deformation of a Fe-18Mn-3Si-0.6C-0.4Al steel reveals that the twinning is mainly dominant at a stress below 900 MPa, above which the twinning behavior is largely outweighed by phase transformation from the face-centered-cubic (FCC) γ-austenite to the hexagonal-close-packed (HCP) ε-martensite. In the deformed grains, the distribution of ε-martensite is parallel with the twin boundary. Both the well-known {111}γ//{0001}ε relationship and an additional {111}γ//{11–21}ε orientation relation were identified. After the phase transformation, both phases deformed further with the lattice rotating around an axis perpendicular to the tensile direction. Transition from the twinning dominant behavior to the phase transformation induced plasticity effect is explained by the grain orientation dependence of the effective stacking fault energy (ESFE). An asymmetric and inverse relationship between the width of stacking faults (SF) and the ESFE is obtained from the density functional theory (DFT). The tensile stress always increases proportionally with the SF width in the twinning favorable grains and thus a decreasing ESFE. The replacement of twinning activities by phase transformation could be due to both the nucleation site of ε-martensite at the SF of the twin boundary and the decrease of the ESFE in grains which originally favors the twinning.

Original languageEnglish
Pages (from-to)273-284
Number of pages12
JournalActa Materialia
Volume161
DOIs
StatePublished - Dec 2018

Funding

QX thanks the funding from the Natural Science Foundation of China (grant no. 51571025 ) and the sponsor by the Laboratory Directed Research and Development (LDRD) Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy. Resources at the Spallation Neutron Source, U.S. DOE Office of Science User Facilities operated by ORNL, were used in this research. First principle calculations (ZP and ME) were sponsored by the U.S. Department of Energy , Office of Science , Basic Energy Sciences , Materials Science and Engineering Division . This research used resources of the Oak Ridge Leadership Computing Facility, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725 .

Keywords

  • DFT
  • Effective stacking fault energy
  • Stacking fault probability
  • TRIP
  • TWIP

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