Microstructure and texture evolution of a high manganese TWIP steel during cryo-rolling

Abstract

The influence of rolling at 77 K and 293 K to a true strain of 2.66 on the microstructure and texture evolution and mechanical behavior of a TWIP Fe-0.3C-23Mn-1.5Al steel was quantified. The microstructure evolution at both temperatures of deformation was associated with an increase in the dislocation density and extensive twinning, following by the development of a cell structure and shear bands. Rolling at both temperatures was associated with a formation of the Copper-type texture in the beginning of deformation and transition to the Brass-type texture during further rolling. Intensive formation of ε-martensite was observed at 77 K. The transformation of twin boundaries into arbitrary high-angle grain boundaries due to interaction with lattice dislocations led to the formation of grains/subgrains with the size of 30-60 nm after cryo-rolling to a strain of 2.66. Rolling at both temperatures resulted in continuous increase of strength of the steel and decrease of ductility. The ultimate tensile strength was 1993 MPa and 1824 MPa after rolling to a true thickness strain of 2.66 at 77 K and 293 K, respectively. Qualitative analysis of contributions of different strengthening mechanisms was performed.

Evolution of Microstructure and Mechanical Properties of a CoCrFeMnNi High-Entropy Alloy during High-Pressure Torsion at Room and Cryogenic Temperatures

“…However, deformation twins are usually much thinner than annealing twins and intersect grains. The thickness of deformation twins in a single phase fcc microstructure is usually several tens of nanometers [12,21], whereas the thickness of annealing twins can reach several micrometers [22]. Some of the deformation twins are indicated with arrows in Figure 2b,c.…”

From High-Manganese Steels to Advanced High-Entropy Alloys

“…On the other hand, C-Mn short range ordered clusters contribute to the splitting of partial dislocations and ease the onset of deformation twinning [26]. In turn, in the C-free HEA, a more prolonged stage of deformation by dislocation slip retards the initiation of deformation twinning and delays the formation sequence of twin-matrix lamellae, their rotation into the rolling plane, and the subsequent onset of shear banding [27][28][29][30][31][32][33], which are thus shifted to higher strains. Hence, the related formation of a pronounced Brass-type texture with the typical texture components-Brass, Goss, CuT and γ-fiber-is shifted to higher degrees of thickness reduction during rolling of the HEA.…”

Substructure Development and Deformation Twinning Stimulation through Regulating the Processing Path during Multi‐Axial Forging of Twinning Induced Plasticity Steel

“…As is reported in Table , during conventional rolling the dislocation slip accommodates the strain at lower strains and at higher strains twinning becomes the predominant deformation mechanism. According to the previous researches, the deformation twinning would be suppressed at 60% reduction during rolling and the further strains are accommodated by shear bands without any contribution of twinning and slip . The deformation mechanism in severe plastic deformation processes such as HPT is quite different from rolling condition.…”

“…Therefore, deformation twinning and substructure development both contribute in strain hardening during the 3rd compression. It is worth mentioning that the previous works regarding the deformation behavior of TWIP steels through cold rolling, high pressure torsion, and equi‐channel angular pressing all reported the suppression of twinning at the early stage of processing; these are summarized in Table .…”

“…As is seen in Figure f, after one MAF pass the initial texture components distributions are reassembled to the new deformation texture. The most of researches on the deformation textures of low SFE TWIP steels subjected to the cold working, reported the formation of specified fibers texture . However, the new fiber texture in the ODF section is obtained after one MAF pass which is formed by the high intensity of the E {111} <011> and the Cube {001} <100> components.…”