The Influence of Warm Rolling Reduction on Microstructure Evolution, Tensile Deformation Mechanism and Mechanical Properties of an Fe-30Mn-4Si-2Al TRIP/TWIP Steel

Abstract

The effects of warm rolling reduction ratio ranging from 20% to 55% on microstructure evolution, the tensile deformation mechanism, and the associated mechanical properties of an Fe-30Mn-4Si-2Al TRIP/TWIP steel were studied. The warm rolling process resulted in the formation and proliferation of sub-structure, comprising dislocations, deformation twins as well as shear bands, and the densities of dislocation and twins were raised along with the increase in rolling reduction. The investigated steel, with a fully recrystallized state, exhibited a single ε-TRIP effect during the room temperature tensile deformation, on top of dislocation glide. However, the formation and growth of twin lamellae and ε-martensite were detected simultaneously during tensile deformation of the warm rolled specimen with rolling reduction of 35%, leading to a good balance between high yield strength of 785 MPa, good total ductility of 44%, and high work hardening rate. As the rolling reduction increased to 55%, the specimen revealed a relatively low work hardening rate, due to the high dislocation density, and dislocation glide was the main deformation mechanism. As a result, a tensile deformation mechanism that started from a single ε-martensitic transformation moved to a bi-mode of ε-martensitic transformation accompanied with deformation twinning, and finally to dislocation glide with the increasing warm rolling reduction was proposed.

The Effects of Recrystallization on Strength and Impact Toughness of Cold-Worked High-Mn Austenitic Steels

“…These rolling strips were elongated in the same direction as the grain boundaries drawn in the hot rolling direction, as shown in Figure 2a. After the cold-working process, deformation twin and slip bands were observed inside grains in Figure 2b-d while deformation twinning increased with an increase in the cold-working level from 5% to 30% [8]. Therefore, the cold-working process induced deformation twinning in the austenite grains, and the density of twinning increases with increasing cold-working reduction leading to grain subdivision.…”

“…The high-Mn austenitic steels show a fully austenite phase at room temperature and have good mechanical properties by deformation mechanisms at low temperatures [7]. These steels demonstrate mechanical twinning instead of phase transformation to martensite after plastic deformation, which is called twinning-induced plasticity (TWIP) [8]. These mechanisms depend on stacking fault energy (SFE), and the SFE generally increases as Mn, Cr and Ni content increase in TWIP steels.…”

Effects of Ni Content on Reversible Deformation-Induced Martensitic Transformation of Fe–Mn–Cr–Si–Ni Alloy Under Uniaxial Deformation

“…In TRIP/TWIP steels, since the work-hardening rate should be closely related to martensitic transformation, three to four different deformation stages are generally presented according to the true strain dependency of the work-hardening rate (dr/de) of as-annealed specimens during tensile deformation. [19,20] The work-hardening rate profiles of the specimens in this study exhibit only three stages, namely, stages I, II, and IV (Figure 4). In stage I, the strain hardening rate drops pronouncedly according to the dynamic recovery of dislocations.…”

Improving Mechanical Properties of a Forged High-Manganese Alloy by Regulating Carbon Content and Carbide Precipitation

“…In favor of the TRIP-TWIP-coupled effect [5,31,33,34] and grain refinement strengthening, the annealed specimens obtained a higher yield strength and elongation. During subsequent annealing, accompanying the formation of annealing twins, the FCC phase continued to transform, with the TRIP-TWIP coupled effect being exerted [35][36][37][38].…”