Heat Input Effect on the Microstructure of Twinning-Induced Plasticity (TWIP) Steel Welded Joints Through the GTAW Process

MRS Advances ◽  
2018 ◽  
Vol 3 (64) ◽  
pp. 3949-3956
Author(s):  
H. Hernández-Belmontes ◽  
I. Mejía ◽  
V. García-García ◽  
C. Maldonado
Keyword(s):  
Phase Transformations ◽  
Heat Input ◽  
Twip Steel ◽  
Research Work ◽  
Second Phase ◽  
Current Electrode ◽  
Weld Joints ◽  
Average Grain Size ◽  
Gtaw Process ◽  
Twip Steels

ABSTRACTHigh-Mn Twinning Induced Plasticity (TWIP) steels are an excellent alternative in the design of structural components for the automotive industry. The TWIP steels application allows weight reduction, maintaining the performance of vehicles. Nowadays the research works focused on TWIP steel weldability are relative scarce. It is well-known that weldability is one of the main limitations for industrial application of TWIP steel. The main goal of this research work was studied the effect of heat input on the microstructural changes generated in a TWIP steel microalloyed with Ti. A pair of welds were performed through Gas Tungsten Arc Welding (GTAW) process. The GTAW process was carried out without filler material, using Direc Current Electrode Negative (DCEN), tungsten electrode EWTh-2 and Ar as shielding gas. The microstructure and average grain size in the fusion (FZ) and heat affected zone (HAZ) were determined by light optical metallography (LOM). Elements segregation in the FZ was evaluated using point and elemental mapping chemical analysis (EPMA) by Scanning Electron Microscopy and Electron Dispersive Spectroscopy (SEM-EDS). Phase transformations were evaluated using X-ray diffraction (XRD). Finally, the hardness were measured by means of Vickers microhardness testing (HV500). The results show that the FZ is characterized by a dendritic solidification pattern. Meanwhile, the HAZ presented equiaxed grains in both weld joints. On the other hand, the TWIP-Ti steel weldments did not present austenite phase transformations. Nevertheless, the FZ exhibited variations in the chemical elements distribution (Mn, Al, Si and C), which were higher as the heat input increases. Finally, the heat input reduced the microhardness of TWIP-Ti steel weld joints. Although post-welding hardness recovery was detected, which is associated with precipitation of Ti second-phase particles.

Microstructural and Mechanical Characterization of Autogenous GTAW Weld in High-Manganese Austenitic Steel Ti-Containing with Thermal Analysis

MRS Advances ◽  
2018 ◽  
Vol 3 (64) ◽  
pp. 3963-3969
Author(s):  
V. García-García ◽  
I. Mejía ◽  
F. Reyes-Calderón
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Weld Joint ◽  
Heat Input ◽  
Thermal Field ◽  
Twip Steel ◽  
Experimental Results ◽  
Butt Weld ◽  
Average Grain Size ◽  
Gtaw Process

ABSTRACTThe welding heat input has been pointed out as a main limiting factor for TWinnig Induced Plasticity (TWIP) steel weldability. Scarce research works have been focused on the study of application and effects of the Gas Tungsten Arc Welding (GTAW) process in the TWIP steel, especially in higher thickness plate. In this research work was conducted a detailed analysis of a butt weld joint performed in plates of TWIP steel microalloyed with titanium (TWIP-Ti) of 6.3 mm thickness. The autogenous GTAW process with low heat input was applied. The analysis considered grain size measurements, second phases identification, post-weld mechanical properties (microhardness) and the welding thermal field. A Finite Element Model (FEM), validated through experimental results, allowed correlating metallurgical results with the thermal field. Likewise, the phases prediction carried out by means of JMatPro 9.0 software during solidification process as well as the estimation of particle precipitation were in good agreement with the experimental results. These predictive diagrams were calculated taking into account the TWIP-Ti steel chemical composition, the grain size measured in critical weld regions and experimental cooling rates. The low heat input improved the microstructural conditions in the heat affected zone (HAZ) whose average grain size and precipitate particles, like (C, N)Ti, promoted good mechanical properties as compared to the base material (as-solution condition). Some particles like Al2O3 y MnS produced microporosities in the HAZ. Despite this, the weld joint did not present hot cracking in the FZ-HAZ interface.

Characterization of inclusions and second-phase particles in high-Mn TWIP steels microalloyed with Ti, Ti/B, Nb, V and Mo, in as-solutioned condition

MRS Advances ◽  
2020 ◽  
Vol 5 (59-60) ◽  
pp. 3023-3033
Author(s):  
D. Mijangos ◽  
I. Mejía ◽  
J. M. Cabrera
Keyword(s):  
Mechanical Properties ◽  
Research Work ◽  
High Strength ◽  
Second Phase ◽  
Energy Dispersion Spectroscopy ◽  
Austenitic Phase ◽  
Electron Microscopies ◽  
Second Phase Particles ◽  
Twip Steels ◽  
Microalloying Elements

AbstractIn recent years there has been an increase in the field of research of advanced steels that have excellent mechanical properties combining high strength with excellent ductility. Within this range of advanced steels are the stable austenitic phase steels at room temperature of twinning induced plasticity known as TWIP. An important aspect to highlight about TWIP steels is their addition with different microalloying elements, generally less than 0.20 wt. %, which are forming precipitated phases such as carbides, nitrides and carbonitrides, and directly or indirectly control and/or modify microstructure and mechanical properties in these steels. Microalloying elements can cause a higher degree of hardening due to the formation of precipitates and grain refinement. The present research work studies the inclusions and second-phase particles formed in Fe–21Mn–1.3Si–1.6Al TWIP steels microalloyed with Ti, Nb, V, Mo and Ti/B in as-solution condition. TWIP steels melted in induction furnace were homogenized and hot-rolled at 1200 °C with reduction of 60 %. Subsequently, rolled plates were solubilized at 1100 °C followed by water quench. Thermodynamics-based predictions of inclusions and second-phases of different TWIP steels were carried out using JMatPro®V.9.1.2. Metallographic characterization was carried out by light optical and scanning electron microscopies (LOM, SEM), while second-phase particles characterization was performed using energy dispersion spectroscopy (SEM-EDS). Also, Vickers microhardness tests were carried out in accordance to ASTM E92 standard. In general, results showed the formation of inclusions of AlN and MnS at higher temperatures, which act as nuclei points for the precipitation particles of each type of microalloying element (TiN, TiC, Nb (C, N), VC and MoC) at lower temperatures. The studied TWIP steels exhibit similar microhardness values, since the microalloying elements are mostly dissolved in solid solution. The TWIP steels microalloyed with V and Ti exhibited the highest microhardness values.

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.

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.

Weldability of High-Mn Austenitic Twinning-Induced Plasticity (TWIP) Steel Microalloyed with Nb

MRS Advances ◽  
2017 ◽  
Vol 2 (62) ◽  
pp. 3899-3908 ◽  
Author(s):  
I. Mejía ◽  
H. Hernández-Belmontes ◽  
C. Maldonado
Keyword(s):  
Heat Affected Zone ◽  
Twip Steel ◽  
Research Work ◽  
Welding Process ◽  
X Ray Diffraction ◽  
Austenite Stability ◽  
Gas Tungsten Arc ◽  
Solution Condition ◽  
Gtaw Process ◽  
Arc Welding Process

ABSTRACTThe objective of this research work is to study the weldability of a Nb microalloyed TWIP steel through welding nuggets generated by Gas Tungsten Arc Welding process. Weldability was examined by microstructural changes in the fusion zone (FZ) and heat affected zone (HAZ) using light optical metallography (LOM), segregation in the nuggets was evaluated using elemental mappings of chemical analysis by Scanning Electron Microscopy and Electron Dispersive Spectroscopy (SEM-EDS), phase transformations were evaluated using X-ray diffraction (XRD) and the hardness properties were examined using Vickers microhardness testing (HV25). Experimental results show that microstructure of welding nuggets consists of austenitic dendritic grains in the FZ and equiaxed grains in the HAZ. FZ width and HAZ grain growth tend to increase as the heat input increases. Additionally, the studied Nb-containing TWIP steel showed segregation in the FZ, where Mn and Si segregated in the interdendritic regions, while Al and C preferentially segregated in dendritic areas. In general, the data obtained by XRD indicated that GTAW process did not affect austenite stability. Finally, the welding nuggets of studied TWIP steel showed lower microhardness values than the as-solution condition (starting condition). However, the heat affected zone showed hardened areas, which are associated with NbC precipitation hardening.

Effect of Ti Microaddition on Cavitation Behavior During Uniaxial Hot-Tensile of Fe-22Mn-1.5Al-1.3Si-0.5C Austenitic TWIP Steel

2016 ◽  
Vol 1812 ◽  
pp. 123-128 ◽  
Author(s):  
Antonio E. Salas-Reyes ◽  
Ignacio Mejía ◽  
José M. Cabrera
Keyword(s):  
Grain Boundary ◽  
Crack Growth ◽  
Fracture Behavior ◽  
Twip Steel ◽  
Research Work ◽  
Grain Boundary Sliding ◽  
Crack Growth Behavior ◽  
Premature Failure ◽  
Damage And Fracture ◽  
Twip Steels

ABSTRACTIt is well-known that metal and alloys develop internal cavities when subjected to uniaxial or multiaxial tensile strains at elevated temperature. In most cases, cavitation may lead to premature failure during forming. Therefore, damage and fracture behavior imposes significant limitations in hot metal-forming processes. Although high-Mn austenitic TWIP steels exhibit a unique combination of strength and ductility, cavitation during hot working is one issue that must be tackled. The aim of this research work is to determine the effect of Ti microaddition on cavity mechanisms of Fe-22Mn-1.5Al-1.3Si-0.5C TWIP steel under uniaxial hot-tensile condition at 800 °C and constant true strain rate of 10-3 s-1. For this purpose, light optical (LOM) and scanning electron (SEM) microscopies and image analysis were applied to quantify cavities formation along longitudinal section of deformed samples near to the fracture surface. The number of cavities greater than 10 µm (critical length) in non-microalloyed and Ti microalloyed TWIP steels were 2.75 and 3.75 cavities/mm2, respectively. On the other hand, average cavity area was 125 and 152 µm2, respectively. Both TWIP steels showed cavities type “r”, “l” and “A”. Finally, Ti microaddition to TWIP steel resulted in a predominant brittle fracture behavior due to finer grain-boundary precipitation, which weakens grains cohesion and accelerates crack growth by grain-boundary sliding. In this case, crack growth behavior is explained in terms of a void interconnection mechanism.

Dry Sliding Wear Behavior of a High-Mn Austenitic Twinning Induced Plasticity (TWIP) Steel Microalloyed with Ti

2015 ◽  
Vol 1765 ◽  
pp. 59-64 ◽  
Author(s):  
V.H. Mercado ◽  
I. Mejía ◽  
A. Bedolla-Jacuinde
Keyword(s):  
Wear Resistance ◽  
Twip Steel ◽  
Wear Behavior ◽  
Research Work ◽  
Protective Layer ◽  
Dry Sliding Wear ◽  
Dry Sliding ◽  
Limited Information ◽  
Average Wear ◽  
Twip Steels

ABSTRACTHigh-Mn austenitic twinning induced plasticity (TWIP) steels are the object of intense worldwide scientific study due to the promising combination of strength and ductility of these alloys. Mechanical behavior of this family of new generation steels has been extensively studied recently. However, limited information regarding their tribological properties is available in the literature. The aim of this research work is to study the wear behavior of a high-Mn austenitic Fe–20Mn–1.5Si–1.5Al–0.4C TWIP steel microalloyed with Ti. The wear behavior was evaluated under dry sliding condition by the ‘‘pin-on-ring’’ method. For this purpose, solution-treated samples were worn for 10 km against a counterface disc made of hardened AISI M2 steel, under loads of 52, 103 and 154 N, and at speeds of 0.20, 0.60 and 0.86 m/s. The wear resistance was evaluated from the average wear rate. Wear debris and worn surfaces were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (SEM-EDS). The Ti addition to TWIP steel slightly improved the wear resistance particularly at a speed of 0.86 m/s and at loads of 52 and 103 N. Results show that the wear resistance increases with increasing sliding speed. This is attributed to the formation of an oxide layer acting as a protective layer against wear, which suggests that the main wear mechanism for the studied TWIP steel under these conditions is oxidative.

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.

Recrystallization in Ultra-Fine Grain Structures of AA3104 Alloy Processed by ECAP and HPT

2012 ◽  
Vol 715-716 ◽  
pp. 346-353
Author(s):  
H. Paul ◽  
T. Baudin ◽  
K. Kudłacz ◽  
A. Morawiec
Keyword(s):  
High Pressure Torsion ◽  
Deformation Mode ◽  
Second Phase ◽  
Orientation Measurement ◽  
Angular Pressing ◽  
Second Phase Particles ◽  
Average Grain Size ◽  
The Matrix ◽  
Electron Microscopes ◽  
Different Strains

The objective of this study was to determine the effect of deformation mode on recrystallization behavior of severely deformed material. Commercial purity AA3104 aluminum alloy was deformed via high pressure torsion and equal channel angular pressing to different strains and then annealed to obtain the state of partial recrystallization. The microstructure and the crystallographic texture were analysed using scanning and transmission electron microscopes equipped with orientation measurement facilities. The nucleation of new grains was observed in bulk recrystallized samples and during in-situ recrystallization in the transmission microscope. Irrespective of the applied deformation mode, a large non-deformable second phase particles strongly influenced strengthening of the matrix through deformation zones around them. It is known that relatively high stored energy stimulates the nucleation of new grains during the recrystalization. In most of the observed cases, the growth of recrystallized grains occurred by the coalescence of neighboring subcells. This process usually led to nearly homogeneous equiaxed grains of similar size. The diameter of grains in the vicinity of large second phase particles was only occasionally significantly larger than the average grain size. Large grains were most often observed in places far from the particles. TEM orientation mapping from highly deformed zones around particles showed that orientations of new grains were not random and only strictly defined groups of orientations were observed.

Determination of Heat Input in Tungsten Inert Gas and Laser Welding of Type Optim 960 QC Structural Steel Using Adams’ Equation for 2-D Heat Distribution

2017 ◽  
Vol 750 ◽  
pp. 45-52
Author(s):  
Sveto Cvetkovski
Keyword(s):  
Laser Welding ◽  
Heat Input ◽  
Arc Welding ◽  
Research Work ◽  
Laser Beam Welding ◽  
Peak Temperature ◽  
Efficiency Coefficient ◽  
Zone Recrystallization ◽  
Welding Processes

The heat input during conventional arc welding processes can be readily calculated knowing the power taken from the power source. The efficiency coefficient can be taken from the appropriate literature standards. Here, the intention of the performed research work was to develop a procedure for determination of heat input in arc and laser welding processes implementing Adams equation - modified Rykalin equation for two dimensional heat distributions (2-D). To realize this idea, it is necessary to determine two characteristic temperatures points in the HAZ with known peak temperature, and to determine distance between them. Implementing measured values for distance in Adams’ equation, heat input in arc welding can be directly determined in arc welded joints.In laser beam welding, the absorption of the beam in the metal is not known, so that the welding heat input cannot be calculated directly, and direct implementation of Adam’s equation is not possible i.e. absorption coefficient has to be determined first, and after that calculation of heat input is possible.The peak temperatures corresponding to specific microstructures can be obtained by performing welding simulation, by the Gleeble 1500 simulator in our case. As one of the peak temperatures, the melting temperature can be used corresponding to the fusion line, so that at least one characteristic peak temperature such as coarse grain zone, fine grin zone, intercritical zone, recrystallization, has to be determined by the simulation.Performed research showed that obtained values for heat input using Adam’s equation correspond pretty well with standard equation for heat input in arc welding.

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