Increase In Cold Rolling Reduction Research Articles

Optimizing the microstructure and mechanical properties of Fe-30.5Mn–8Al-1.0C lightweight austenitic steel through thermomechanical treatment

This study presents an application of thermomechanical treatment technique (cold rolling followed by aging treatment) to significantly enhance the mechanical properties of a novel lightweight austenitic steel (Fe-30.5Mn–8Al-1.0C), mainly focusing on the impacts of cold-rolling reduction and subsequent aging temperature on its microstructure, texture, and tensile properties. It has been found that the dislocation density increased with an increase in cold rolling reduction from 25 % to 45 % and reached a saturation at a reduction of 45 %, facilitating the activation of deformation twins and accelerating κ-carbide precipitation. The tensile strength of the steel exhibited significant improvement with increased cold-rolling reduction, owing to the combined effects of dislocation strengthening and the Hall–Petch mechanism. A tensile strength as high as 1.6 GPa was obtained in samples treated by 65 % cold rolling reduction. Aging treatment can generally enhance the ductility in most samples, owing to an improved work hardening capability induced by κ-carbide precipitation. Consequently, an optimum thermomechanical process, involving a 45 % cold rolling reduction followed by aging at 600 °C for 10 min, was established to achieve a better combination of tensile strength (1428 ± 35.8 MPa) and elongation (26.7 ± 1.3 %), showcasing its potential for applications demanding high strength and exceptional ductility.

Microstructure and Texture Evolution in Cold-Rolled and Annealed Oxygen-Free Copper Sheets.

Commercial oxygen-free copper sheets were cold-rolled with reduction rates ranging from 20% to 87% and annealed at 400, 500 and 600 °C. The microstructure and texture evolution during the cold-rolling and annealing processes were studied using optical microscopy (OM), scanning electron microscopy (SEM) and electron back-scattered diffraction (EBSD). The results show that the deformation textures of {123}<634> (S), {112}<111> (Copper) and {110}<112> (Brass) were continuously enhanced with the increase in cold-rolling reduction. The orientations along the α-oriented fiber converged towards Brass, and the orientation density of β fiber obviously increased when the rolling reduction exceeded 60%. The recrystallization texture was significantly affected by the cold-rolling reduction. After 60% cold-rolling reduction, Copper and S texture components gradually decreased, and the {011}<511> recrystallization texture component formed with the increase in annealing temperature. After 87% cold-rolling reduction, a strong Cube texture formed, and other textures were inhibited with the increase in annealing temperature. The strong Brass and S deformation texture was conducive to the formation of a strong Cube annealing texture. The density of the annealing twin boundary decreased with the increase in annealing temperature, and more annealing twin boundaries formed in the oxygen-free copper sheets with the increase in cold-rolling reduction.

Tailored carburization gradient microstructure and enhanced wear properties of M50NiL steel via introduced prior cold rolling

M50NiL (Chinese grade G13Cr4Mo4Ni4V) steel is widely used in aircraft bearing raceways that require excellent wear resistance under harsh service conditions. However, the impact of cold rolling, as an advanced forming process for bearings, on the carburization process and wear properties is still unknown. Therefore, the gradient microstructure and dry sliding wear performance of the cold-rolled M50NiL disc against Si3N4 ceramic ball have been investigated. The results show that with the increase of cold rolling reduction to 40 %, the carbon concentration of surface is increased by 17.1 % due to the growing percentage of grain boundaries (GB) and dislocation density. The carbide content is increased by 29 % with average size declined by 21.2 %, which contributes to a 7.4 % increase in the surface hardness. Additionally, the wear test indicates that the average friction coefficient and wear rate are respectively reduced by 17.3 % and 47.1 % when the rolling reduction increases to 40 %. After prior rolling, the wear mechanism changes from severe abrasion to adhesion and tribochemical reactions accompanied with the enhancement of wear properties, which is mainly attributed to the uniform distribution of finer carbides with higher fraction on the surface and subsurface.

Effect of cold rolling reduction on the precipitation behavior of σ phase in 2906 duplex stainless steel

The effect of cold rolling reduction on the precipitation of σ phase at 800 °C in the 2906 DSS was investigated. The results show that the precipitation rate of the σ phase is improved with the increase of rolling reduction, and the maximum volume fraction is limited to 15%–20% due to the exhaust of ferrite. Improving the rolling reduction could promote the diffusion of Cr, Ni, Mo departing from ferrite and Ni, Mo departing from austenite during the following aging process. The contents of Cr, Ni and Mo increased suddenly and then keep stable in the σ phase, which preferentially nucleated around the narrow ferrite regions. The increase of cold rolling reduction is favorable for σ phase precipitation due to the promoted diffusion of Cr, Ni and Mo elements, as well as the decrease in thickness of ferrite/austenite lamellar interface. The σ phase/austenite interface is incoherent without orientation relationship between the σ phase and austenite, the orientation relationship between ferrite and austenite illustrates (02-2)γ//(-13-2)α and (33-1)γ//(-33-2)α, and the σ phase becomes coarsen and continuous along the ferrite/austenite interface.

Effect of cold rolling and solution treatment on β stability and mechanical properties of a metastable β-Ti alloy

This work investigated the influence of cold rolling reduction and solution treatment on β stability and mechanical properties of a metastable β-Ti alloy (Ti–5Mo–2Cr–Fe–3Zr). The microstructure, phase composition and mechanical properties were analyzed by SEM, XRD, EBSD, TEM and tensile test. Deformation mechanism of cold-rolled alloy includes the reversion of athermal α" to β phase, deformation-induced {332}<113>β twinning and ω phase, dislocation slip, and microbands. The phase compositions of samples with different cold rolling reductions after solution treatment are different. Compared with 12.8% cold rolling and solution treatment (CR12.8%ST), the 27.7% and 51.3% cold rolling and solution treatment (CR27.7%ST and CR51.3%ST) have less α" phase and more β and ω phases, indicating that the β stability of CR27.7%ST and CR51.3%ST is higher than that of CR12.8%ST. Furthermore, the tensile strength and elongation of the samples increase simultaneously with the increase of cold rolling reduction. The CR51.3%ST alloy has good mechanical properties including a high ultimate tensile strength of 948 MPa, a uniform elongation of 15.7%, and an ultra-high strain hardening rate of 2000 MPa.

The Effect of CRITSIMA Process Parameters on the Microstructure Evolution and Element Segregation of Semi-Solid CuSn10P1 Alloy Billet

In this paper, based on the as-cast CuSn10P1 alloy. Semi-solid CuSn10P1 alloy billet was prepared by cold-rolled isothermal treatment strain-induced melting activation (CRITSIMA). The effects of cold-rolling reduction, isothermal temperature, and isothermal time on the microstructure of semi-solid copper alloy billet were studied by metallographic microscope and Image-Pro Plus software. The changes of primary elements in as-cast and semi-solid microstructure were analyzed briefly by a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). The results show that with the increase of cold rolling reduction, the average grain diameter of semi-solid microstructure decreases gradually, the average grain roundness increases first and then decreases, and the liquid fraction of the microstructure remains unchanged. During semi-solid isothermal treatment, with the increase of isothermal temperature and the extension of isothermal time, the average grain diameter increases gradually, the average grain roundness increases first and then decreases, and the liquid fraction increases gradually. When cold rolling reduction is 30%, isothermal temperature is 900 ℃, and isothermal time is 20 min, a better microstructure can be obtained. The average grain diameter, average grain roundness, and liquid fraction of semi-solid alloy billet are 66.45 μm, 0.71, and 12.78%, respectively. Sn and P diffuse from the intergranular liquid to the grain inside during the isothermal treatment from as-cast to semi-solid.

Unidirectional cold rolling of Fe-21Cr-5Mn-1.5Ni alloy – Microstructure, texture and magnetic properties

In the present work, changes in microstructure, texture and magnetic properties during unidirectional cold rolling of a Fe-21Cr-5Mn-1.5Ni alloy were investigated. For microstructural characterization, scanning electron microscope (SEM) and electron backscattered diffraction (EBSD) were used, while for bulk texture measurements, X-ray diffraction (XRD) was used. Magnetic measurements (M-H and B-H curves) were used to characterize the strain induced martensite (SIM). The band thickness (thickness of grain along normal direction (ND)) reduced significantly more in austenite, than in ferrite with increasing deformation (cold rolling). Also, during deformation, more strain was partitioned in austenite than in ferrite. The saturation magnetization increased with increase in cold rolling reduction and SIM was ∼ 11% after 80% cold rolling. The as-received sample showed strong cube ({100} 〈100〉 ) and Brass ({110} 〈112〉 ) in austenite and strong α (RD//〈110〉 ) and γ (ND//〈111〉 ) fibres in ferrite. After 80% cold rolling, strong Brass ({110} 〈112〉 ) and Goss ({110} 〈001〉 ) were developed in austenite, while the existing α and γ fibres further strengthened in ferrite. The area under the B-H curve was found to be proportional to strain. Both texture and strain were found to be responsible for this increase.

Study of Cold Rolling on the Transformation Mechanism, Microstructure, and Properties of 304 Austenitic Stainless Steel

The work hardening mechanism and microstructure properties of 304 austenitic stainless steel (304 ASS) during cold rolling are studied by means of electron backscatter diffraction (EBSD), a transmission electron microscope (TEM), X‐ray diffraction (XRD), hardness test, and permeability measurement. Meanwhile, the mechanical properties and permeability properties of 304 ASS with different cold rolling reductions are investigated. The results show that when the cold rolling reduction is in the range of 5−20%, there are two kinds of phase transformations (γ → ϵ → α′ and γ → α′) in the 304 ASS. With increase in cold rolling reduction (cold rolling reduction ≥ 23%), γ → α′ became the main phase transformation. It is known that α′‐martensite significantly affects the permeability of 304 ASS. To obtain the weak magnetic property that meets the needs of end users, the cold rolling reduction should be controlled at 5−10%.

Microstructure Evolution and Texture Characteristics of Pure Nickel N6 During Cold Rolling Process

A single-pass large-deformation rolling method was used to study the effect of cold rolling degree on the microstructure, microtextural evolution, and grain orientation during the cold rolling of pure nickel N6. The results show that the microstructure evolves from micro-bands to lamellar-bands with the increase of cold rolling reduction, and the fraction of coincidence site lattice boundaries always decreases. Starting from an initially low imposed strain (20% of the cold rolling reduction), the deformed microstructure is mainly composed of Goss, rotated Goss, P, and Brass orientations. When cold rolling reduction exceeds 50%, the shear textures appear and other textures remain but their intensities decrease. The strong shear stress on the surface of the rolled plate causes the normal cold-rolled texture dominated by Cu{112} , S{123} , Brass{011} to rotate around the transverse direction to form a shear texture composed of shear4{112} and {110}∥RD fiber textures.

Multistep Cross Rolling of UNS S32101 Steel: Microstructure, Texture, and Magnetic Properties

In the present study, effect of multistep cross rolling (MSCR) on microstructure, texture, and magnetic properties has been investigated for UNS S32101 steel. UNS S32101 steel consisting of almost equal proportion of ferrite and austenite was 80% cold cross rolled in multiple steps. The microstructures were characterized using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD), while crystallographic texture was determined by x-ray diffraction (XRD). Microstructure showed decrease in band thickness and spacing for both austenite and ferrite with increased cold-rolling reduction. Lenticular bulges were the main feature of microstructure after 80% cold rolling, indicating the presence of strain-induced martensite (SIM). Hysteresis loops were also measured in order to characterize other parameters associated with deformation and SIM. The magnetic anisotropy decreased, while coercivity (Hc), area under the B-H loop and magnetic losses increased with an increase in cold-rolling reduction. Hc was found to be directly proportional to the amount of reduction during cold rolling and inversely proportional to equivalent circle grain size. As-received sample showed strong cube ({100} ) with strong Brass ({110} ) in austenite and strong α (rolling direction, RD// ) and γ (normal direction, ND// ) fibers in ferrite. For 80% rolling, strong Brass and Goss ({110} ) were developed in austenite, while strong rotated cube ({100) ) and γ-fiber were obtained in ferrite.

Texture Development During Cold Rolling of a β-Ti Alloy: Experiments and Simulations

Microstructure evolution and texture development during cold rolling of a Ti15333 alloy were systematically investigated in the present work. Texture was simulated using mean-field [Visco-Plastic Self-Consistent (VPSC) and Taylor] models. Evolution of crystallographic texture was also simulated using the Visco-Plastic Fast Fourier Transform (VPFFT) model. The as-received samples (in the hot-forged and hot-rolled condition) were cold rolled unidirectionally up to 20, 40, 60 and 80 pct thickness reductions. Increase in the cold-rolling reduction resulted in changes in the crystallographic texture as well as grain morphology. The initial hot-rolled sample consisted of in-grain shear bands that were aligned approximately ± 35 to 40 ° with respect to the sample rolling direction. Shear band density gradually increased with the increase in cold-rolling reduction, and these bands usually represent narrow zones of intense strain. α (RD//〈110〉) and γ (ND//〈111〉) fibers were observed in all the cold-rolled samples. The volume fraction of both these fibers was found to be highest for the 80 pct deformed sample. For mean-field simulations, the normalized difference of the texture index (normalized TIdiff) was found to be a good criterion to represent the match between the simulated and experimental texture. The affine model (VPSC) was found to give a good match with the experimental texture compared to the Taylor models. The γ-fiber and α-fiber were always overestimated in mean-field VPSC simulations. Extensive shear band formation could be the possible reason for mismatch between the simulated and experimental texture. For VPFFT simulations, the general texture evolution involved the intensification of the γ-fiber and α-fiber texture. Simulated texture was reasonably well predicted quantitatively with VPFFT, analyzed based on the volume fraction of the different texture fibers/components.

Effect of cold rolling reduction on texture, recrystallization and mechanical properties of UNS S32304 Lean Duplex stainless steel

The effect of cold rolling reduction on the texture, extended recovery, recrystallization and mechanical properties of UNS S32304 Lean Duplex stainless steel was investigated. EBSD analysis showed that α′-martensite transformation in austenite phase caused a shear band formation in ferrite phase. An austenite grain with {110}<112> Brass component transformed to α′-martensite with {001}<110> rotated cubic component was found according to the Kurdjumov-Sachs (K-S) orientation relationship after 63% cold rolling reduction. Evidence that extended recovery and discontinuous recrystallization occurred in the ferrite phase was observed. The increase in cold rolling reduction caused an increase in the softened fraction and the fraction of grains with GOS<1° mainly due to the extended recovery in the center. The increase in cold rolling reduction causes higher stored energy and affects the discontinuous recrystallization in the austenite phase. On the other hand, the austenite texture was not influenced and a decrease in its intensity was only observed during annealing. The uniform elongation and total elongation remained approximately constant after the softened fraction reached 0.92 and the complete recrystallization of austenite phase.

Texture development during multi-step cross rolling of a β titanium alloy: Experiments and simulations

In the present work, microstructure and texture evolution during multi-step cross rolling of a β-Ti alloy was investigated. The as-received samples were cross rolled in a laboratory rolling mill to 20%, 40%, 60% and 80% thickness reduction. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe the changes in microstructure, while the changes in bulk texture were evaluated using X-ray diffraction. The as-received sample consisted of equiaxed as well as elongated grains. Equivalent circle average grain size (AGS) and the average band thickness (ABT) along normal direction (ND) for as-received β-Ti sample was 50 ± 3 μm and 27 ± 1.8 μm respectively. The AGS and ABT decreased with increase in cold rolling reduction (for 80% cold rolled sample ABT was 7.5 ± 2.3 μm). Another important feature was the presence of strain localizations in the cold rolled samples, the frequency of which increased with increase in strain. The as-received sample showed the presence of α (rolling direction RD//<110>) and γ (ND//<111>) fibers. At highest strain (80% cold rolling), rotated cube ({100}<110>) component was found to be significantly stronger than the γ-fiber texture. Visco-Plastic Self Consistent (VPSC) model was used for the simulation of texture during cold cross rolling. Qualitatively, full constraint VPSC model was found to match reasonably well with the experimental data. α-Fiber, γ-fiber and rotated cube were over estimated in the VPSC texture predictions.

Effect of cold rolling and annealing on microstructure and properties of a new resource-saving duplex stainless steel Fe–19Cr–0.6Al–12Mn

An Fe–19Cr–0.6Al–12Mn duplex stainless steel with an optimized alloy composition of Ni replaced by Mn and Cr partially replaced by Al was developed to avoid the edge cracking, which is a common defect in the hot rolling of traditional two-phase stainless steels. The newly developed duplex stainless steel could be hot-rolled in the single-phase ferrite (α) region by controlling rolling temperature and the single-phase ferrite microstructure was retained on water cooling. To obtain the two-phase stainless steel product with ferrite and austenite (γ) microstructure, cold rolling and annealing were carried out, and appropriate cold rolling reduction and annealing process parameters were determined. The significant impact of annealing on microstructure, mechanical properties and pitting resistance of the experimental steel was studied. It was observed that with the increase in cold rolling reduction, the number of γ nucleation points was dramatically increased leading to the precipitation of more γ at α grain boundaries after annealing. During annealing at 800 °C and with the increase in annealing time, the austenite fraction was increased with a lower rate and remained almost constant when the annealing time was greater than 4 h. With the increase in annealing temperature, the austenite fraction decreased gradually in the temperature range of 750–860 °C. Good combination of strength, ductility and excellent pitting resistance was obtained by cold rolling to 80% reduction and annealing at 800 °C for 4 h. Grain refinement and the existence of Σ3 boundaries played a vital role in improving the pitting resistance of the experimental steel. With good combination of strength, ductility and corrosion resistance, the newly developed duplex stainless steel is expected to be a new resource-saving dual-phase stainless steel.

Cold rolling of an interstitial free (IF) steel—Experiments and simulations

In the present work, the microstructure and texture evolution of interstitial free (IF) steel during cold rolling was studied experimentally and via simulations. Stored energy and geometrically necessary dislocation (GND) density maps were calculated from the electron backscattered diffraction (EBSD) data. The evolution of crystallographic texture, stress and strain during deformation were simulated using a full field crystal plasticity Fast Fourier Transform (CPFFT) model implemented in DAMASK (the Düsseldorf Advanced Material Simulation Kit), an open source code. The simulations for cold rolling of 2D i.e. EBSD data were done considering activation of one slip system ({110}<111>) as well as two slip systems ({110}<111>+{112}<111>), while for 3D data (statistical microstructure generated via DREAM.3D) two slip systems were used. The stored energy increased with the increase in cold rolling reduction in general, the increase being more in γ fiber (ND//<111>) grains than the grains with other orientations. In experiments as well as simulations, the volume fraction of γ fiber and α fiber (RD//<110>) increased with cold rolling. The simulations done using two slip systems matched reasonably well with the experiments. The stress and strain during deformation increased and showed similar trend for both 2D and 3D simulations.

Adjusting the microstructure evolution, mechanical properties and deformation behaviors of Fe-5.95Mn-1.55Si-1.03Al-0.055C medium Mn steel by cold-rolling reduction ratio

For a representative medium Mn steel with the actual chemical composition of Fe-5.95 Mn-1.55Si-1.03Al-0.055 C (wt. %), the effect of cold-rolling deformation on microstructural evolution and mechanical properties was investigated systematically. The thickness of coarse δ-ferrite grains decreases with the increase of cold-rolling reduction, and when the cold-rolling reduction ratio reaches up to a certain value, these δ-ferrite grains can be broken into small pieces due to the severe plastic deformation. Additionally, a critical cold-rolling reduction ratio for recrystallization exists. Below this critical reduction value, the medium Mn steel after austenite reverted transformation (ART) annealing remains lath-shaped structure originating from the initial martensitic morphology, and when recrystallization occurs, however, submicron equiaxed grains dominate. The initial microstructure before ART annealing, which is usually determined by cold-rolling reduction, strongly influences not only the martensitic/ferritic matrix, but also reverted austenite grains. Non-recrystallization matrix promotes the formation of acicular reverted austenite, whereas recrystallization forces the austenite grains spherical and promotes the grain size of austenite homogenizing. Under the situation of non-recrystallization, the cold-rolling reduction prior to ART annealing only has a negligible effect on the final mechanical properties. However, the occurrence of recrystallization results in not only the yielding plateau, i.e., discontinuous yielding, but also the remarkable increase of yield strength.

The effect of cold rolled reduction ratios on grain boundary character and mechanical properties of the SUS301L austenitic stainless steel

With the rapid development of the rail vehicle industry, SUS301L austenitic stainless steel becomes the main material of rail vehicles, due to its cold processing performance, which has attracted much attention. In order to study the effect of grain boundary feature distribution on the properties of 301L stainless steel during cold deformation. 301L stainless steel samples with a cold rolling reduction of 3%, 5%, 9%, and 24% were prepared. The microstructure, mechanical properties and corrosion resistance of samples with different grain boundary characteristics were studied by means of OM, EBSD, universal testing machine and three-electrode electrochemical workstation. The result shows that with the increasing of the cold rolling reduction, grain orientation 〈111〉 is significantly weakened, the grain boundary of small angles gradually increases. Meanwhile, the grain boundary of large angle the strong grain boundary of Σ ≤ 29 gradually decreases. 301L stainless steel high ductility and toughness can be improved by obtaining a frequency of low Σ values in the coincident site lattice(CSL) grain boundaries. The microstructure and grain size is gradually getting smaller. The strength increased, while ductility, toughness, and the corrosion resistance reduced. The grain boundary of Σ3 gradually decreases with the increase of cold rolling reduction, but the reduction range of 9%∼24% is not significant.

Microstructure characteristics, strengthening and toughening mechanism of rolled and aged multilayer TWIP/maraging steels

The multilayer structure design of steels can accomplish the purpose of strengthening and toughening. Multilayer TWIP/Maraging steel with high strength, high toughness and interfacial shear strength of 564 MPa is obtained by vacuum hot rolling, subsequent cold rolling and aging treatment. It is found that hot rolling can achieve effective interface bonding ability. Grain refinement, twinning proliferation and dislocation strengthening are generated in TWIP layers with the increase of cold rolling reduction, which can improve the strength and toughness of multilayer steel. However, when the reduction reaches more than 90%, the nanocrystalline and nano twins are appeared in TWIP layers, and plasticity is seriously reduced. The proper adjustment of the cold rolling and ageing process, interface alloying elements diffusion, twinning proliferation, nano-precipitation strengthening, and work hardening can obviously improve the interface bonding ability, strength and toughness, this research provides theoretical basis and experimental support for the lamination design and strengthening-toughening mechanism of a series of metal materials.

Microstructure and texture development in Ti-15V-3Cr-3Sn-3Al alloy – Possible role of strain path

In the present investigation, evolution of microstructure and texture was studied for a β titanium alloy during cold rolling (unidirectional rolling (UDR) and cross rolling (multi-step cross rolling (MSCR) and two step cross rolling). For both UDR and MSCR of initially hot rolled alloy consisting of elongated and equiaxed grain structure, the occurrence of shear bands inside the grains was the main feature of the microstructure. The density of these shear bands was dependent on the cold rolling reduction and strain path and was found to be orientation dependent. Shear bands preferentially occurred in γ-fiber (normal direction (ND)//〈111〉) oriented grains. The regions with shear bands had higher hardness than the regions without shear bands, and {111}〈112〉 component of the γ-fiber was found to be more susceptible to formation of shear bands. The orientation dependence of these shear bands was analyzed within the framework of Dillamore's plastic instability criterion. During UDR, strong α and γ-fibers were observed after highest strain (ε = 1.6), while strong rotated cube ({100}〈110〉) texture developed after MSCR at highest strain (ε = 1.6). The volume fraction of both α and γ fibers gradually increased with the increase in cold rolling reduction during UDR. For MSCR, the rotated cube component gradually increased with increase in cold rolling reduction. In solution annealed β-Ti alloy with equiaxed grain structure, α and γ fibers were formed after highest strain (ε = 1.6) during UDR. However, due to large grain size, both α and γ fibers were discontinuous. The texture development was found to be more strongly dependent on the strain path than the initial microstructure during cold rolling.

Effect of Cold Rolling on Microstructure and Mechanical Properties of AISI 304N Stainless Steel

Effect of cold rolling at room temperature on microstructure and mechanical properties of a nitrogen-bearing austenitic stainless steel AISI 304N was studied in this paper. The cold rolling reductions from 5% to 90% were adopted for the cold rolling test. Microstructures were observed by an optical microscopy, volume fractions of strain induced α’-martensite were measured by a ferritescope, and deformation induced transformation was investigated by X-ray diffraction. Hardness and tensile tests were carried out to determine the mechanical properties. The results showed that with increase of cold rolling reduction, the volume fraction of strain induced α’-martensite increased while grains were elongated along the rolling direction. The formation of α’-martensite and the lamellar grains resulted in the significant strengthening of the steel and substantial decrease of elongation.