Dynamic energy absorption of ultrafine-grained TWIP steel under axial impact loading

2018 ◽  
Vol 1 (1) ◽  
pp. 51-64 ◽  
Author(s):  
Mahmoud H. A. Gadelhaq ◽  
Atef S. Hamada ◽  
Mohsen A. Hassan ◽  
Jukka Kömi
Keyword(s):  
Energy Absorption ◽  
Twip Steel ◽  
Cast Steel ◽  
Tensile Tests ◽  
High Yield ◽  
Ultrafine Grain ◽  
Recrystallization Annealing ◽  
Ultrafine Grained ◽  
Cold Worked ◽  
The Impact

This research focuses on studying the dynamic energy absorption property of a micro-alloyed TWIP steel, which was proposed to act as a connection part between car front bumper and chassis in middle-class cars for vehicle safety. The studied TWIP steel was designed based on stacking fault energy of 25mJ/m2. The as-cast steel was deformed in hot and cold rolling to 2 mm thick sheets. Subsequently, recrystallization annealing was applied to the heavily cold-worked steel at different temperatures to obtain different ultrafine grain structures. The mechanical properties were determined using tensile tests. It was observed that at 900°C, the optimal temperature for strengthening by vanadium carbide precipitation, it was too low to complete recrystallization. However, at 1000°C, an ultrafine-grained structure was formed with high yield, tensile strengths and elongation of about 700MPa, 1100MPa and 30% respectively. Accordingly, TWIP steel was used for crash analysis simulation using ANSYS Workbench R14.5. Thin-walled square columns of that steel were employed for energy absorbance during a collision regarding progressive plastic deformation. The crashworthiness criteria were studied under different impact conditions with thicknesses of 0.25, 0.5, 0.75 and 1 mm. Simulation results showed high initial peak force during the impact. Hence, a trigger mechanism of an external tapered plunger was proposed to reduce it. This combination of new material and innovative design promises enhancement car safety.

Application of Texture Analysis for Optimizing Thermo-Mechanical Treatment of a High Mn TWIP Steel

2014 ◽  
Vol 922 ◽  
pp. 213-218 ◽  
Author(s):  
Christian Haase ◽  
Luis Antonio Barrales-Mora ◽  
Dmitri A. Molodov ◽  
Günter Gottstein
Keyword(s):  
Cold Rolling ◽  
Texture Analysis ◽  
Twip Steel ◽  
Uniform Elongation ◽  
High Yield ◽  
Processing Route ◽  
Recrystallization Annealing ◽  
Deformation Degree ◽  
Texture Measurement ◽  
Wide Range

A recently introduced processing route consisting of cold rolling and recovery annealing allows the production of TWIP steels with high yield strength along with appreciable uniform elongation due to the thermal stability of mechanically induced nanoscale twins. A wide range of strength-ductility combinations was obtained using recovery and recrystallization annealing of 30%, 40%, and 50% cold-rolled Fe-23Mn-1.5Al-0.3C TWIP steel. Texture measurement during cold rolling and annealing was proven to be a suitable tool to determine the optimal deformation degree and annealing time for this processing method. As a consequence, texture analysis can be used to predict the final materials properties.

Synthesis of high-strength W–Ta ultrafine-grain composites

2008 ◽  
Vol 23 (1) ◽  
pp. 133-139 ◽  
Author(s):  
R.T. Ott ◽  
X.Y. Yang ◽  
D.E. Guyer ◽  
S. Chauhan ◽  
D.J. Sordelet
Keyword(s):  
High Strength ◽  
High Energy ◽  
High Temperature Phase ◽  
High Yield ◽  
Ultrafine Grain ◽  
Temperature Phase ◽  
Composite Powders ◽  
Ultrafine Grained ◽  
Submicron Scale ◽  
The Individual

Bulk samples of an ultrafine-grained tungsten–tantalum composite alloy have been synthesized by consolidating mechanically milled composite powders. The grain growth during densification is limited due to the submicron-scale layering of the individual metals in the composite particles and the relatively low sintering temperature (1300 °C). The ultrafine microstructure of the high-density (∼99% theoretical density) samples leads to a high yield stress of ∼3 GPa under quasi-static uniaxial compression. A tendency for Ta-rich solid-solution formation during densification was observed, and the high-temperature phase equilibria in the composite powders were examined further using high-energy x-ray diffraction at temperatures up to 1300 °C.

Specific Features of Static, Impact, and Fatigue Fracture of the 0.09%C-0.08%Mo-0.03%Nb-0.06%V Steel with Ultrafine-Grained Structure

2008 ◽  
Vol 584-586 ◽  
pp. 281-286 ◽  
Author(s):  
L.R. Botvina ◽  
Marat R. Tyutin ◽  
V.P. Levin ◽  
Y.A. Demina ◽  
I.A. Panteleev ◽  
...  
Keyword(s):  
Tensile Tests ◽  
Dynamic Fracture Toughness ◽  
Fracture Mechanisms ◽  
Plastic Deformation Zone ◽  
Initial Structure ◽  
Initial State ◽  
Surface Microrelief ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
The Impact

The mechanical properties and fracture mechanisms of the 0.09%C-0.08%Mo-0.03%Nb- 0.06%V steel in the initial state and with the ultrafine-grained (UFG) structure obtained by equalchannel angular pressing (ECAP) have been estimated. The investigation included the static and cyclic tensile tests, the impact tests at room and lower temperatures with automatic recording of force-displacement diagram, and the analysis of both the fracture surface microrelief and the evolution of plastic deformation zone by replica method. It is established that the grain refinement increases the ultimate strength and yield strength, but decreases plasticity and impact toughness and raises fatigue growth rate and the critical temperature of ductile–brittle transition. The dynamic fracture toughness of the material after ECAP as compared with that of the material with the initial structure decreases due to the raising of the critical brittleness temperature.

scholarly journals Unique transition of yielding mechanism and unexpected activation of deformation twinning in ultrafine grained Fe-31Mn-3Al-3Si alloy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yu Bai ◽  
Hiroki Kitamura ◽  
Si Gao ◽  
Yanzhong Tian ◽  
Nokeun Park ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Twip Steel ◽  
Deformation Twinning ◽  
Ultrafine Grain ◽  
Yield Drop ◽  
Grain Sizes ◽  
Deformation Twins ◽  
Ultrafine Grained ◽  
The Mean

AbstractTensile mechanical properties of fully recrystallized TWIP steel specimens having various grain sizes (d) ranging from 0.79 μm to 85.6 μm were investigated. It was confirmed that the UFG specimens having the mean grain sizes of 1.5 μm or smaller abnormally showed discontinuous yielding characterized by a clear yield-drop while the specimens having grain sizes larger than 2.4 μm showed normal continuous yielding. In-situ synchrotron radiation XRD showed dislocation density around yield-drop in the UFG specimen quickly increased. ECCI observations revealed the nucleation of deformation twins and stacking faults from grain boundaries in the UFG specimen around yielding. Although it had been conventionally reported that the grain refinement suppresses deformation twinning in FCC metals and alloys, the number density of deformation twins in the 0.79 μm grain-sized specimen was much higher than that in the specimens with grain sizes of 4.5 μm and 15.4 μm. The unusual change of yielding behavior from continuous to discontinuous manner by grain refinement could be understood on the basis of limited number of free dislocations in each ultrafine grain. The results indicated that the scarcity of free dislocations in the recrystallized UFG specimens changed the deformation and twinning mechanisms in the TWIP steel.

Strain Rate Sensitivity of Ultrafine Grained FCC- and BCC-Type Metals

2006 ◽  
Vol 503-504 ◽  
pp. 781-786 ◽  
Author(s):  
Johannes May ◽  
Heinz Werner Höppel ◽  
Matthias Göken
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Testing Temperature ◽  
Ultrafine Grain ◽  
Ultrafine Grain Size ◽  
Ultrafine Grained

The dependence of the strain rate sensitivity (SRS) of α-Fe and Al 99.5, as typical representatives of fcc- and bcc-type metals, on the testing temperature and with respect to the microstructure is investigated. In particular, the differences between conventional grain size (CG) and ultrafine grain size (UFG) are pointed out. UFG Al 99.5 generally shows an elevated SRS compared to CG Al 99.5. In case of α-Fe the SRS of the UFG state is decreased at room temperature, but increased at 200 °C, compared to the CG state. It is shown that the SRS also influences the ductility of UFG-metals in tensile tests.

High Speed Deformation of Ultrafine Grained TWIP Steel

2007 ◽  
Vol 561-565 ◽  
pp. 107-110 ◽  
Author(s):  
Rintaro Ueji ◽  
Kenji Harada ◽  
Noriyuki Tsuchida ◽  
Kazutoshi Kunishige
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Twip Steel ◽  
Ultrafine Grain ◽  
Grain Sizes ◽  
Ultrafine Grain Size ◽  
Ultrafine Grained ◽  
Wide Range ◽  
Twip Steels ◽  
Large Work

Tensile properties of twinning induced plasticity (TWIP) steels (31%Mn-3%Al-3%Si-Fe) with various mean grain sizes ranging from ultrafine grain size (1.1μm) to conventional one (35.5μm) at a wide range of strain rates from 10-3sec-1 to 103sec-1 were studied. The ultrafine grained TWIP steel exhibits a large work hardening and keeps an adequate elongation at any strain rate. The strength held to the Hall-Petch relationship at each strain rate and the Hall-Petch slopes do not change largely.

Effect of Grain Structure on the Mechanical and Corrosion Behavior of Advanced Medium Mn Stainless TWIP Steel

2020 ◽  
Vol 998 ◽  
pp. 15-20 ◽  
Author(s):  
Mahmoud H.A. Gadelhaq ◽  
Atef S. Hamada ◽  
Ibrahim M. Ghayad ◽  
Antti Järvenpää ◽  
Matias Jaskari ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Twip Steel ◽  
Electron Backscatter Diffraction ◽  
Corrosion Behaviour ◽  
Cold Deformation ◽  
Tensile Tests ◽  
Grain Structure ◽  
Recrystallization Annealing ◽  
Significant Deterioration

The influence of recrystallization annealing on the microstructure, mechanical properties and corrosion behaviour of an austenitic TWIP steel bearing medium Mn and V alloying was investigated. The steel undergone a heavy cold deformation of 65 % reduction. Subsequently, recrystallization annealing at 1000 °C and 1100 °C for 15 min was conducted to achieve different grain structures. The microstructural evolution was studied using optical microscopy and electron backscatter diffraction technique. Mechanical properties were determined using tensile tests at room temperature. Corrosion behaviour was measured by cyclic potentiodynamic polarization at 3.5 pct NaCl. For comparison, austenitic stainless-steel Type 201 was used in this study. It was observed that at 1000 °C, a non-uniform austenitic grain structure with vanadium carbides distributed throughout the matrix was obtained. However, a coarse grain structure without carbides was induced at 1100 °C. The fine-grained structure enhanced at 1000 °C exhibited higher strength and good ductility. Contrary to this, the corrosion results showed that a significant deterioration in the corrosion resistance could be observed in sodium chloride solution for the achieved structure at 1000 °C compared to 201 stainless steel.

Preparation and Mechanical Properties of Ultrafine Grained Metals

1990 ◽  
Vol 195 ◽  
Author(s):  
B. Gunther ◽  
A. Baalmann ◽  
H. Weiss
Keyword(s):  
Yield Strength ◽  
Tensile Tests ◽  
Coarse Grained ◽  
Strengthening Effect ◽  
Ultrafine Grained ◽  
Concurrent Processes ◽  
Evaporation Technique ◽  
Cold Worked ◽  
20 Nm ◽  
Coble Creep

ABSTRACTUltrafine—grained polycrystalline metallic components (Cu, Au, Fe) have been prepared by means of the inert gas evaporation technique combined with an integrated uniaxial cold compaction device. The average grain sizes ranaed typically from 20 nm to about 100 nm. The microstructure and Imourity content of the as-pressed samples have been investigated by means of TEM and AES, respectively. The yield strength of ultrafine (30 nm) grained Cu specimens obtained in tensile tests compares well with respective values for heavily cold—worked coarse grained copper. Al slight heat treatment (150ºC/30min) improves the strain—to—fracture at slightly reduced yield strength values. The results are discussed within the picture of two concurrent processes determining the strength of ultrafine grained metals: Coble creep vs. grain boundary strengthening effect.

Formability of Ultrafine Grained Steel

2010 ◽  
Vol 638-642 ◽  
pp. 3543-3548 ◽  
Author(s):  
S. Torizuka ◽  
Eijiro Muramatsu
Keyword(s):  
Uniform Elongation ◽  
Tensile Tests ◽  
Ultrafine Grain ◽  
Strain Behavior ◽  
Bainitic Steels ◽  
Ultrafine Grained ◽  
Inherent Feature ◽  
Ultralow Carbon ◽  
Reduction In Area ◽  
Ultrafine Grained Steel

Ultrafine grain refinement to 1 m deteriorates the uniform elongation in the tensile tests of steels. Such loss of ductility has been argued to be an inherent feature of the ultrafine-grained steels. While uniform elongation is a measure of ductility of the material, reduction in area in tensile tests is also an important measure of ductility. Ultrafine grained steels with different carbon contents from ultralow carbon to high carbon were produced through warm caliber rolling and evaluated for their stress-strain behavior along with the reduction in area. It was found that the reduction in area- tensile strength balance is far better than the conventional ferrite+pearlite steels and even superior to bainitic steels for all materials tested in the present study. Formability of ultrafine grained steel is examined by applying to make a micro screw. Good formability was verified by this process.

scholarly journals Low-carbon cast microalloyed steel intercritically heat-treated at different temperatures: microstructure and mechanical properties

2021 ◽  
Vol 21 (2) ◽  
Author(s):  
Hadi Torkamani ◽  
Shahram Raygan ◽  
Carlos Garcia Mateo ◽  
Yahya Palizdar ◽  
Jafar Rassizadehghani ◽  
...  
Keyword(s):  
Carbon Content ◽  
Volume Fraction ◽  
Block Size ◽  
Tensile Tests ◽  
Total Elongation ◽  
Martensite Phase ◽  
Low Carbon ◽  
Steel Increase ◽  
Different Temperatures ◽  
The Impact

AbstractIn this study, dual-phase (DP, ferrite + martensite) microstructures were obtained by performing intercritical heat treatments (IHT) at 750 and 800 °C followed by quenching. Decreasing the IHT temperature from 800 to 750 °C leads to: (i) a decrease in the volume fraction of austenite (martensite after quenching) from 0.68 to 0.36; (ii) ~ 100 °C decrease in martensite start temperature (Ms), mainly due to the higher carbon content of austenite and its smaller grains at 750 °C; (iii) a reduction in the block size of martensite from 1.9 to 1.2 μm as measured by EBSD. Having a higher carbon content and a finer block size, the localized microhardness of martensite islands increases from 380 HV (800 °C) to 504 HV (750 °C). Moreover, despite the different volume fractions of martensite obtained in DP microstructures, the hardness of the steels remained unchanged by changing the IHT temperature (~ 234 to 238 HV). Applying lower IHT temperature (lower fraction of martensite), the impact energy even decreased from 12 to 9 J due to the brittleness of the martensite phase. The results of the tensile tests indicate that by increasing the IHT temperature, the yield and ultimate tensile strengths of the DP steel increase from 493 to 770 MPa, and from 908 to 1080 MPa, respectively, while the total elongation decreases from 9.8 to 4.5%. In contrast to the normalized sample, formation of martensite in the DP steels could eliminate the yield point phenomenon in the tensile curves, as it generates free dislocations in adjacent ferrite.

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