scholarly journals Graded Grain Structure to Improve Hydrogen-Embrittlement Resistance of TWIP Steel

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1045
Author(s):  
Seok Weon Song ◽  
Taekyung Lee ◽  
Chong Soo Lee
Keyword(s):  
Hydrogen Embrittlement ◽  
Twip Steel ◽  
Low Cycle Fatigue ◽  
High Strength ◽  
Grain Structure ◽  
Coarse Grained ◽  
Slow Strain Rate Test ◽  
Hydrogen Penetration ◽  
Twip Steels ◽  
Elongation To Failure

The high strength of twinning-induced plasticity (TWIP) steels makes them vulnerable to the hydrogen embrittlement (HE) phenomenon, thereby limiting their potential applications. This study suggests inducing a graded grain structure (GGS) in a Fe-17Mn-0.8C TWIP steel through shot peening and subsequent heat treatment to solve the problem. The microstructures and fracture surfaces of GGS TWIP steel were compared with those of conventionally manufactured TWIP steel possessing a uniform grain structure (UGS). Compared with the conventional UGS TWIP steel, GGS steel showed similar tensile properties with a yield strength of 310 MPa, tensile strength of 1060 MPa, and elongation-to-failure of 135%. It also exhibited moderately enhanced low-cycle fatigue (LCF) resistance in terms of fatigue life (8196 cycles to failure) compared with the UGS steel (7201 cycles). Furthermore, GGS TWIP steel exhibited a marked improvement in HE resistance, both in the monotonic (by a slow-strain-rate test) and cyclic deformation modes (by the LCF test) in a hydrogen environment. A relatively fine-grained (d = 15.6 μm) surficial area enhanced the HE resistance by inhibiting hydrogen penetration and decreasing twin density, while the coarse-grained (d = 74.6 μm) interior promoted the LCF resistance by suppressing crack growth.

On the Utility of Crystal Plasticity Modeling to Uncover the Individual Roles of Microdeformation Mechanisms on the Work Hardening Response of Fe-23Mn-0.5C TWIP Steel in the Presence of Hydrogen

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
B. Bal ◽  
M. Koyama ◽  
D. Canadinc ◽  
G. Gerstein ◽  
H. J. Maier ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrogen Embrittlement ◽  
Twip Steel ◽  
Strain Response ◽  
Deformation Response ◽  
Self Consistent ◽  
Twip Steels ◽  
Simulation Results ◽  
The Individual ◽  
Experimental Findings

This paper presents a combined experimental and theoretical analysis focusing on the individual roles of microdeformation mechanisms that are simultaneously active during the deformation of twinning-induced plasticity (TWIP) steels in the presence of hydrogen. Deformation responses of hydrogen-free and hydrogen-charged TWIP steels were examined with the aid of thorough electron microscopy. Specifically, hydrogen charging promoted twinning over slip–twin interactions and reduced ductility. Based on the experimental findings, a mechanism-based microscale fracture model was proposed, and incorporated into a visco-plastic self-consistent (VPSC) model to account for the stress–strain response in the presence of hydrogen. In addition, slip-twin and slip–grain boundary interactions in TWIP steels were also incorporated into VPSC, in order to capture the deformation response of the material in the presence of hydrogen. The simulation results not only verify the success of the proposed hydrogen embrittlement (HE) mechanism for TWIP steels, but also open a venue for the utility of these superior materials in the presence of hydrogen.

The Mechanical and Deformation Behavior of TWIP Steel Prepared by Directional Solidification

2014 ◽  
Vol 783-786 ◽  
pp. 761-765 ◽  
Author(s):  
Dan Wang ◽  
Kun Wang ◽  
Zi Mu Shi ◽  
Fu Sheng Han
Keyword(s):  
Mechanical Properties ◽  
Strain Hardening ◽  
Twip Steel ◽  
True Strain ◽  
Longitudinal Direction ◽  
True Stress ◽  
Grain Structure ◽  
Directionally Solidified ◽  
Twip Steels ◽  
Columnar Grain

A directionally solidified TWIP steel (Fe-25Mn-2.5Al-2.5Si) was prepared by liquid metal cooling technology. The microstructure and mechanical behavior were examined and compared with usually solidified samples. The directionally solidified TWIP steel shows a typical columnar grain structure, and the maximum true stress and true strain along the longitudinal direction of the sample are 1060MPa and 71% respectively. As a comparison, the usually solidified samples shows an equiaxed grain microstructure with the maximum true stress and true strain of only 994MPa and 58%, respectively. Moreover, the two solidification modes also lead to very different strain hardening behavior, particularly in the changes of strain hardening rate with strain. This suggests that the grain boundary plays a key role in the mechanical properties of TWIP steels, and changing the grain boundaries can be effective to improve the comprehensive mechanical properties of TWIP steels.

Influence of Severe Plastic Deformation on Mechanical Properties of an AA5024 Alloy

2016 ◽  
Vol 879 ◽  
pp. 1317-1322 ◽  
Author(s):  
Anna Mogucheva ◽  
Diana Yuzbekova ◽  
Tatiana Lebedkina ◽  
Mikhail Lebyodkin ◽  
Rustam Kaibyshev
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
High Strength ◽  
Coarse Grained ◽  
Type B ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Elongation To Failure ◽  
Dislocation Strengthening

The paper reports on the effect of severe plastic deformation on mechanical properties of an Al-4.57Mg-0.35Mn-0.2Sc-0.09Zr (in wt. pct.) alloy processed by equal channel angular pressing followed by cold rolling (CR). The sheets of the 5024 alloy with coarse grained (CG) structure exhibited a yield stress (YS) near 410 MPa and an ultimate tensile strength (UTS) of 480 MPa, while the YS and UTS of this material with ultrafine-grained (UFG) structure increased to 530 and 560 MPa, respectively. On the other hand, the elongation to failure decreased by a factor of 2 and 4 after CR and CR following ECAP, respectively. It was shown that dislocation strengthening attributed to extensive CR plays a major role in achieving high strength of this alloy. Besides these macroscopic characteristics, jerky flow caused by the Portevin-Le Chatelier (PLC) instability of plastic deformation was examined. The formation of UFG structure results in a transition from mixed type A+B to pure type B PLC serrations. No such effect on the serrations type was observed after CR.

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.

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.

Dual-phase nanocrystalline Ni–Co alloy with high strength and enhanced ductility

2010 ◽  
Vol 25 (2) ◽  
pp. 401-405 ◽  
Author(s):  
Liyuan Qin ◽  
Jianshe Lian ◽  
Zhonghao Jiang ◽  
Guoyong Wang ◽  
Qing Jiang
Keyword(s):  
Grain Size ◽  
Room Temperature ◽  
High Strength ◽  
High Rate ◽  
Coarse Grained ◽  
Dual Phase ◽  
Ductile Materials ◽  
Average Grain Size ◽  
Elongation To Failure ◽  
Critical Scale

A dual-phase (DP) Ni–66.7%Co alloy with an average grain size of 16 nm was fabricated by electrodeposition. It exhibited an ultimate tensile strength of 1800–2080 MPa, together with an elongation to failure of 10–15% at room temperature. The remarkable ductility of this DP alloy with critical scale grains was attributed to its sustained high rate of strain hardening. Its fracture surface showed an unexpected deeply dimpled structure similar to that of coarse-grained ductile materials, which also witnesses the improved ductility.

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.

scholarly journals Tailoring Extra-Strength of a TWIP Steel by Combination of Multi-Pass Equal-Channel Angular Pressing and Warm Rolling

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 518
Author(s):  
Marina Abramova ◽  
Arseniy Raab ◽  
Ruslan Z. Valiev ◽  
Anna Khannanova ◽  
Chong Soo Lee ◽  
...  
Keyword(s):  
Equal Channel Angular Pressing ◽  
Materials Science ◽  
Twip Steel ◽  
Mechanical Performance ◽  
Warm Rolling ◽  
Gradual Transition ◽  
Angular Pressing ◽  
Different Temperatures ◽  
Twip Steels ◽  
Elongation To Failure

Increasing the yield stress of twinning-induced plasticity (TWIP) steels is a demanding task for modern materials science. This aim can be achieved by microstructure refinement induced by heavy straining. We feature the microstructural evolution and mechanical performance of a high-manganese TWIP steel subjected to deformation treatment by different combinations of equal channel angular pressing (ECAP) and rolling at different temperatures. The effect of microstructure on the tensile properties of the steel subjected to the multi-pass ECAP process and to subsequent rolling is reported as well. We show that the combined deformation procedure allows us to further increase the strength of the processed workpieces due to a gradual transition from a banded structure to a heterogeneous hierarchical microstructure consisting of fragments, dislocation configurations and nano- and micro-twins colonies. Rolling of multi-pass ECAP specimens at 375 °C allowed us to achieve an extraordinary strength, the highest among all the investigated cases, while the best trade-off between yield strength and elongation to failure was reached using multi-pass ECAP followed by rolling at 500 °C. This study shows a great potential of using combined deformation techniques to enhance the mechanical performance of TWIP steels.

Mechanical Properties of High Nitrogen - High Strength Stainless Steels in High Pressure Gaseous Hydrogen Environment

2013 ◽  
Author(s):  
Jun Nakamura ◽  
Tomohiko Omura ◽  
Yusaku Tomio ◽  
Hiroyuki Hirata ◽  
Masaaki Terunuma ◽  
...  
Keyword(s):  
High Pressure ◽  
Hydrogen Embrittlement ◽  
Stainless Steels ◽  
High Strength ◽  
Hydrogen Gas ◽  
Gaseous Hydrogen ◽  
Fatigue Properties ◽  
Slow Strain Rate Test ◽  
Chemical Compositions ◽  
High Nitrogen

The susceptibility to hydrogen embrittlement and the fatigue properties of several high nitrogen stainless steels were evaluated by SSRT (Slow Strain Rate Test) and external fatigue test. The tensile properties were evaluated by SSRT in gaseous hydrogen pressurized up to 90MPa in the temperature range from −40 degree C to room temperature. Despite the increase of nitrogen content, high nitrogen stainless steels showed no degradation by hydrogen. The susceptibility to hydrogen embrittlement depended on the chemical compositions. Fatigue properties in high pressure gaseous hydrogen were evaluated by the external cyclic pressurization test using tubular specimens. In this test the tubular specimen was filled with high pressure hydrogen gas filled with hydrogen pressurized up to 90MPa, and the outside of the specimen was cyclically pressurized with water pressurized up to 90MPa. The difference of fatigue life between hydrogen and inert gas was extremely small. Susceptibility to hydrogen embrittlement was discussed based on stability of an austenitic structure.

Revealing the Individual Hardening Effects of Twins, Dislocations, Grain Boundaries and Solid Solution in a Twinning-Induced Plasticity Steel

2016 ◽  
Vol 879 ◽  
pp. 2489-2494
Author(s):  
Zhi Yuan Liang ◽  
Ying Zhuang Liu ◽  
Xu Wang ◽  
Ren Dong Liu ◽  
Ming Xin Huang
Keyword(s):  
Solid Solution ◽  
Flow Stress ◽  
Grain Boundaries ◽  
Twip Steel ◽  
True Strain ◽  
High Strength ◽  
Minor Effect ◽  
Line Profile Analysis ◽  
Twip Steels ◽  
The Individual

Manganese-rich austenitic twinning-induced plasticity (TWIP) steels with high strength and superior ductility have received much attention in the past two decades. Tremendous efforts have been made to explore their unusual hardening behaviour which includes contributions from twins, dislocations, grain boundaries and solid solution. Nevertheless, the individual hardening effects of twins, dislocations, grain boundaries and solid solution on the high strength of TWIP steels are still unclear. In the present work, the flow stress of a TWIP steel was experimentally decomposed into the respective contributions of twins, dislocations, grain boundaries and solid solution. For the forest hardening, synchrotron X-ray diffraction experiments with line profile analysis were carried out to measure the dislocation density. It is found that the yield stress of the present TWIP steel is controlled by solid solution and grain boundary hardening, which contribute to 238.3 and 238.5 MPa, respectively. After yielding, the work-hardening rate is dominated by dislocation multiplication which accounts for up to 922 MPa at a true strain of 0.4, equal to about 60% of the flow stress. In comparison, twins contribute to only 118 MPa at the same true strain, equal to about 8% of the flow stress. In other words, twins have minor effect on the flow stress, in contrast to the current understandings in the literature.

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