scholarly journals Influence of Nb Microaddition on Microstructure and Texture Evolution in a Fe-21Mn-1.3Al-1.5Si-0.5C TWIP Steel under Uniaxial Hot-Tensile Conditions

MRS Advances ◽  
2017 ◽  
Vol 2 (61) ◽  
pp. 3797-3803
Author(s):  
A.E. Salas-Reyes ◽  
I. Mejía ◽  
J.M. Cabrera
Keyword(s):  
Crystallographic Orientation ◽  
Twip Steel ◽  
Electron Backscatter Diffraction ◽  
Texture Evolution ◽  
Constant Strain Rate ◽  
High Strength Steels ◽  
High Strength ◽  
Orientation Distribution ◽  
Deformation State ◽  
Twip Steels

ABSTRACTAdvanced high-strength steels as Twinning Induced Plasticity (TWIP) steels have been developed using microalloying elements and subsequent thermo-mechanical processing techniques. Moreover, under hot-working conditions, these steels undergo significant microstructural changes as a result of preferred crystallographic orientation (texture) of grains. In order to evaluate this behavior, one non-microalloyed and other single Nb-microalloyed TWIP steels were melted in an induction furnace and cast into metal and sand molds. Samples with austenitic grain sizes between 400 and 2000 µm were deformed at 800 °C and strained at a constant strain rate of 10-3 s-1, and deformation state was examined by means of electron backscatter diffraction (EBSD) technique near to the fracture tip. It was found that non-microalloyed TWIP steel solidified in both metal and sand mold exhibits dynamically recrystallized grains. On the other hand, Nb microaddition has a strong influence in TWIP steel retarding the onset of recrystallization kinetics, showing low angle sub-structured grains. Furthermore, it was possible identifying the crystallographic orientation of grains using the inverse pole figures (IPF) and the orientation distribution function (ODF). Weak cube {001}<100> recrystallization and E{111}<110> γ-fiber deformation textures components were detected.

Ab Initio Study of Weldability of a High-Manganese Austenitic Twinning-Induced Plasticity (TWIP) Steel Microalloyed with Boron

2016 ◽  
Vol 1812 ◽  
pp. 35-40 ◽  
Author(s):  
Humberto Hernández-Belmontes ◽  
Ignacio Mejía ◽  
Cuauhtémoc Maldonado
Keyword(s):  
Fusion Zone ◽  
Twip Steel ◽  
Mechanical Performance ◽  
Research Work ◽  
Base Material ◽  
High Strength Steels ◽  
High Strength ◽  
Strengthening Mechanism ◽  
Microstructural Changes ◽  
Twip Steels

ABSTRACTHigh-Mn Twinning-Induced Plasticity (TWIP) steels are advanced high-strength steels (AHSS) currently under development; they are fully austenitic and characterized by twinning as the predominant strengthening mechanism. TWIP steels have high strength and formability with an elongation up to 80%, which allows reduction in automotive components weight and fuel consumption. Since the targeted application field of TWIP steels is the automotive industry, steels need high mechanical performance with good weldability and excellent corrosion resistance. However, there is lack of information about the weldability behavior of these advanced steels. This research work aims to study the weldability of a new generation of high-Mn austenitic TWIP steels microalloyed with B. Weldability was examined using spot welds produced by Gas Tungsten Arc Welding. Microstructural changes were examined using light optical metallography. Segregation of elements in the weld joint was evaluated using point and elemental mapping chemical analysis by Scanning Electron Microscopy and Electron-Dispersive Spectroscopy; while the hardness properties were examined with Vickers microhardness testing (HV25). Experimental results show that the welded joint microstructure consists of austenitic dendritic grains in the fusion zone, and equiaxed grains in the heat affected zone. Notably, the boron microalloyed TWIP steel exhibited poor weldability, showing hot cracking. Additionally, the studied TWIP steels showed a high degree of segregation in the fusion zone; Mn and Si segregated into the interdendritic regions, while Al and C preferentially segregated in dendritic areas. Finally, the welded joints of the TWIP steels showed microhardness values lower than the base material. In general, the present TWIP steels have problems of weldability, which are corroborated with microstructural changes, elements segregation and microhardness loss.

Evaluation of Formability Under Different Deformation Modes for TWIP900 Steel

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Suleyman Kilic ◽  
Fahrettin Ozturk
Keyword(s):  
Twip Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Material Model ◽  
Deformation Analysis ◽  
Advanced High Strength Steels ◽  
Element Simulation ◽  
Springback Prediction ◽  
Deformation Modes ◽  
Prediction Capability

Automotive manufacturers always seek high strength and high formability materials for automotive bodies. Advanced high strength steels (AHSS) are excellent candidates for this purpose. These steels generally show a reasonable degree of formability, in addition to their high strength. One particular type is the twinning-induced plasticity (TWIP) steel, which is a high manganese austenite steel, and represents a second generation in AHSS. In this study, comprehensive deformation analysis of TWIP900CR steel including tensile, bending, Erichsen, and deep drawing of cylindrical cups tests is made. Finite element simulation of U and V shaped bending processes is also performed. Results indicate that the TWIP steel has good mechanical properties and high formability. However, springback is quite significant. The coining force should be considered in order to reduce the amount of springback. For springback prediction, it is found that the Yld2000-2d material model has better prediction capability than the Hill48 model.

scholarly journals Thermal Diffusivity of Traditional and Innovative Sheet Steels

2010 ◽  
Vol 297-301 ◽  
pp. 893-898
Author(s):  
Elena Campagnoli ◽  
Paolo Matteis ◽  
Giovanni M.M. Mortarino ◽  
Giorgio Scavino
Keyword(s):  
Thermal Diffusivity ◽  
Deep Drawing ◽  
Process Model ◽  
Twip Steel ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Carbon Steels ◽  
Low Carbon ◽  
Low Carbon Steels

The low carbon steels, used for the production of car bodies by deep drawing, are gradually substituted by high strength steels for vehicle weight reduction. The drawn car body components are joined by welding and the welded points undergo a reduction of the local tensile strength. In developing an accurate welding process model, able to optimized process parameters and to predict the final local microstructure, a significant improvement can be given by the knowledge of the welded steels thermal diffusivity at different temperatures. The laser-flash method has been used to compare the thermal diffusivity of two traditional deep drawing steels, two high strength steels already in common usage, i.e. a Dual Phase (DP) steel and a TRansformation Induced Plasticity (TRIP) steel, and one experimental high-Mn austenitic TWIP (Twinning Induced Plasticity) steel. The low carbon steels, at low temperatures, have a thermal diffusivity that is 4-5 times larger than the TWIP steel. Their thermal diffusivity decreases by increasing temperature while the TWIP steel shows an opposite behaviour, albeit with a lesser slope, so that above 700°C the TWIP thermal diffusivity is larger. The different behaviour of the TWIP steel in respect to the ferritic deep drawing steels arises from its non ferro-magnetic austenitic structure. The DP and TRIP steels show intermediate values, their diffusivity being lower than that of the traditional deep drawing steels; this latter fact probably arises from their higher alloy content and more complex microstructure.

Wear Resistance Research of Advanced High Strength Steels

2016 ◽  
Vol 850 ◽  
pp. 197-201
Author(s):  
Chao Zhi ◽  
Yi Fei Gong ◽  
Ai Min Zhao ◽  
Jian Guo He ◽  
Ran Ding
Keyword(s):  
Wear Resistance ◽  
Twip Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Wear Performance ◽  
Dp Steel ◽  
Advanced High Strength Steels ◽  
Wear Mode ◽  
Surface Phase Transformation

The wear performance and wear mechanism under two-body abrasion of five advanced high strength steels, i.e. Nanobainite (NB) steel, Tempered Martensitic (TM) steel, Dual Phase (DP) steel, Transformation Induced Plasticity (TRIP) Steel and Twining Induced Plasticity (TWIP) steel were studied. By using the scanning electron microscopy (SEM), we investigated the wearing surface. Phase transformation strengthening behavior was also be discussed by analyzing the surface and sub-surface after abrasion. The results showed that micro-cutting was the major role of wear mode in the condition of two-body abrasion. In the circumstance of two-body abrasion, hardness was an important factor, the property of wear resistance enhanced while the hardness increased except for TM steel. NB steel possessed the best wear resistance which was 1.71 times higher than that of TWIP steel. The retained austenite transformed into martensite which can improve the hardness so that it enhanced the wear resistance of NB steel.

Hydrogen effects on fracture of high-strength steels with different micro-alloying

2015 ◽  
Vol 33 (6) ◽  
pp. 515-527 ◽  
Author(s):  
Olga Todoshchenko ◽  
Yuriy Yagodzinskyy ◽  
Valentina Yagodzinska ◽  
Tapio Saukkonen ◽  
Hannu Hänninen
Keyword(s):  
Chemical Composition ◽  
Electron Backscatter Diffraction ◽  
High Strength Steels ◽  
Thermal Desorption Spectroscopy ◽  
High Strength ◽  
Constant Load ◽  
Carbon Steels ◽  
Hydrogen Induced Cracking ◽  
Load Tests ◽  
Backscatter Diffraction

AbstractConstant load tests of high-strength carbon steels with different micro-alloying using strengths in the range of 1000–1400 MPa were performed at ambient temperature under continuous electrochemical hydrogen charging. Hydrogen markedly affects delayed fracture of all the studied steels. Fractography of the studied steels shows that fracture mechanism depends on the chemical composition of the studied steels and hydrogen-induced cracking exhibits intergranular or transgranular character occurring often in the form of hydrogen flakes. The size and chemical composition of non-metallic inclusions are analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Hydrogen-induced cracking initiates at TiN/TiC particles in steels with Ti alloying. Crack paths are studied with electron backscatter diffraction mapping to analyze crack initiation and growth. The thermal desorption spectroscopy method is used to analyze the distribution of hydrogen in the trapping sites. The mechanisms of hydrogen effects on fracture of high-strength steels are discussed.

Wear Resistance under Non-Lubricated Condition of Nb-Containing TWIP Steel

MRS Advances ◽  
2017 ◽  
Vol 2 (61) ◽  
pp. 3765-3771
Author(s):  
V.H. Mercado ◽  
I. Mejía ◽  
Y. Salinas-Escutia ◽  
A. Bedolla-Jacuinde
Keyword(s):  
Wear Resistance ◽  
Twip Steel ◽  
Wear Behavior ◽  
Research Work ◽  
High Strength Steels ◽  
Mechanical Twinning ◽  
High Manganese ◽  
Structural Applications ◽  
Twip Steels ◽  
Nb Addition

ABSTRACTTwinning induced plasticity (TWIP) steels are one of the most attractive advanced high-strength steels for structural applications due to their unique combination of strength and ductility, which is associated with so-called “mechanical twinning”, where twins act as strong obstacles to the dislocation motion. In this context, Nb addition to TWIP steel increases the strength and refines grain size by nanoscale NbC precipitates. Nowadays, high-manganese TWIP steels are extensively studied. However, information in the specialized literature about their tribological properties is limited. This research work studies the wear behavior of high-manganese austenitic Fe–20Mn–1.5Si–1.5Al–0.4C TWIP steel microalloyed with Nb. The wear behavior was evaluated under non-lubricated sliding condition using the “pin-on-ring” technique. As-solution heat treated samples were worn under loads of 53, 104 and 154 N, and at sliding speeds of 0.22, 0.60 and 0.87 m/s. The wear resistance was evaluated in terms of the loss weight. Wear debris and worn surfaces were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). In general, results show that the wear resistance significantly improves as the sliding speed increases. On the other hand, Nb addition to present TWIP steel produces a slight increase of the wear resistance. Also, it was found that the oxide layer plays a significant role in the wear resistance behavior of this kind of steel.

Implementation of a Constitutive Model for the Mechanical Behavior of TWIP Steels and Validation Simulations

2015 ◽  
Vol 651-653 ◽  
pp. 539-544 ◽  
Author(s):  
Andrea Erhart ◽  
André Haufe ◽  
Alexander Butz ◽  
Maksim Zapara ◽  
Dirk Helm
Keyword(s):  
Constitutive Model ◽  
Metal Forming ◽  
Twip Steel ◽  
Manganese Content ◽  
High Strength ◽  
High Manganese ◽  
Macroscopic Deformation ◽  
Twip Steels ◽  
Stress Dependent ◽  
Crash Loading

High manganese content TWinning Induced Plasticity (TWIP) steels are promising for the production of lightweight components due to their high strength combined with extreme ductility, see [1]. This paper deals with the implementation of a constitutive model for the macroscopic deformation behavior of TWIP steels under mechanical loading with the aim of simulating metal forming processes and representing the behavior of TWIP-steel components – for example under crash loading - with the Finite Element code LS-DYNA®and refers to our recently published papers: [2],[4],[5]. Within the present paper we focus on the implementation of the model formulated in [2] and its extension to stress dependent twinning effects.

Constant Strain Rate Bend Tests on Hydrogen-Embrittled High Strength Steels

JOM ◽  
1956 ◽  
Vol 8 (10) ◽  
pp. 1263-1268
Author(s):  
W. Beck ◽  
E. P. Klier ◽  
G. Sachs
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
High Strength Steels ◽  
High Strength ◽  
Bend Tests

scholarly journals Transformation of the Microstructure of Fe-Cr Steel during Its Production

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 806
Author(s):  
Andrés Núñez ◽  
Irene Collado ◽  
Juan F. Almagro ◽  
David L. Sales
Keyword(s):  
Electron Backscatter Diffraction ◽  
Texture Evolution ◽  
Orientation Distribution ◽  
Basic Material ◽  
Processing Route ◽  
Final Annealing ◽  
Deep Drawability ◽  
Orientation Density ◽  
Backscatter Diffraction ◽  
Process Material

EN 1.4016 stainless steels combine good corrosion resistance with good formability and ductility. As such, their most popular applications are related to sheet forming. During re-crystallisation of Fe-Cr steels, deviations from the desired γ-fibre (gamma fibre, <111>||ND) texture promote a decrease in deep drawability. Additionally, α-fibre (alpha fibre, <110>||RD) has been found to be damaging to formability. In this study, an EN 1.4016 basic material and a modified one with optimised settings as regards to chemical composition and manufacturing process, in order to improve the formability properties, are characterised. The phase diagram, microstructure, Lankford coefficients and Electron Backscatter Diffraction (EBSD) (results confirm the evolution of texture during the processing of ferritic stainless steel. Texture is analysed by the interpretation of Orientation Distribution Function (ODF), using orientation density results for each sample obtained in the processing route. The cube ({001} <100>) and rotated cube ({001} <110>) textures dominate the crystal orientation from the slab until the intermediate annealing stage. After final annealing, there is a texture evolution in both materials; the γ-fibre component dominates the texture, which is much more intense in modified material supported by components that show good deep drawability, {554} <225>, and good transition from hot to cold rolling, {332} <113>. The modified composition and process material delivers a better re-crystallisation status and, therefore, the best drawability performance.

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