In situ high-energy X-ray diffraction mapping of Lüders band propagation in medium-Mn transformation-induced plasticity steels

Abstract

Two-dimensional distributions of microstructural characteristics of austenite (γ ) around the Lüders band in medium-Mn transformation-induced plasticity (TRIP) steel were revealed by in situ highenergy X-ray diffraction. Lüders band propagation leads to significant changes in the volume fraction and lattice strains of austenite. The evolution of the lattice strain of γ -311 accords well with the true yield behavior model and is used to estimate the angle of the Lüders band front with respect to the tensile axis. The modified Williamson-Hall analysis shows that the dislocation density in austenite increased from 7 × 10 14 m −2 to 1.5 × 10 15 m −2 after Lüders band propagation. IMPACT STATEMENTThis in situ high-energy X-ray diffraction study unravels two-dimensional distribution of microstructural evolution during Lüders band propagation in medium-Mn TRIP steels.

Microstructure and Plasticity Evolution During Lüders Deformation in an Fe-5Mn-0.1C Medium-Mn Steel

“…Motomichi KOYAMA, 1,2,3) * Takayuki YAMASHITA, 4) Satoshi MOROOKA, 5) Takahiro SAWAGUCHI, 6) Zhipeng YANG, 1,2) Tomohiko HOJO, 1,2) Takuro KAWASAKI 7) and Stefanus HARJO 7) microstructure, and show a high work-hardening capability. 1,12) Furthermore, the Lüders deformation of medium-Mn steels is characterized by deformation-induced martensitic transformation, 13,14) microscopic strain partitioning, 15) and macroscopic plasticity discontinuity. 16) These three factors strongly correlate with each other.…”

“…Since the initial fraction of austenite was 21%, the microstructural change associated with the deformation band evolution was martensitic transformation from FCC to BCC or body-centered tetragonal (BCT) phases, which is the same as the other medium-Mn steels. 13,14) Hereafter, BCC or BCT martensite is referred to as BCC martensite. Hexagonal close-packed (HCP) martensite was also detected by EBSD, as shown in the phase map.…”

Hierarchical Deformation Heterogeneity during Lüders Band Propagation in an Fe-5Mn-0.1C Medium Mn Steel Clarified through <i>in situ</i> Scanning Electron Microscopy

“…12) In particular, cold-rolled and intercritically annealed medium-Mn steels show distinct Lüders and Portevin-Le Chatelier band propagations. 5,13,14) Furthermore, strain partitioning between austenite-ferrite 10) and deformation-induced martensitic transformation in austenite [15][16][17] during the propagation of the Lüders front also results in deformation heterogeneity at the microstructure scale. In other words, during Lüders band propagation in medium-Mn steels, hierarchical deformation heterogeneities exist, namely, strain partitioning, deformation-induced martensitic transformation in austenite, formations of the deformation bands and mesoscopic Lüders front.…”

Recent Progress of Synchrotron X-Ray Imaging and Diffraction on the Solidification and Deformation Behavior of Metallic Materials

“…High-energy X-ray diffraction microscopy (HEDM) is a monochromatic solution for diffraction contrast imaging [181][182][183][184][185][186][187]. The RisØ National Laboratory, the pioneer of this technique, set up relevant experimental configuration on 1-ID beamline of Advanced Photon Source at Argonne National Laboratory for the first time and developed the corresponding data processing software.…”