Strain hardening recovery mediated by coherent precipitates in lightweight steel

AbstractWe investigated the effect of κ-carbide precipitates on the strain hardening behavior of aged Fe–Mn-Al-C alloys by microstructure analysis. The κ-carbides-strengthened Fe–Mn-Al-C alloys exhibited a superior strength-ductility balance enabled by the recovery of the strain hardening rate. To understand the relation between the κ-carbides and strain hardening recovery, dislocation gliding in the aged alloys during plastic deformation was analyzed through in situ tensile transmission electron microscopy (TEM). The in situ TEM results confirmed the particle shearing mechanism leads to planar dislocation gliding. During deformation of the 100 h-aged alloy, some gliding dislocations were strongly pinned by the large κ-carbide blocks and were prone to cross-slip, leading to the activation of multiple slip systems. The abrupt decline in the dislocation mean free path was attributed to the activation of multiple slip systems, resulting in the rapid saturation of the strain hardening recovery. It is concluded that the planar dislocation glide and sequential activation of slip systems are key to induce strain hardening recovery in polycrystalline metals. Thus, if a microstructure is designed such that dislocations glide in a planar manner, the strain hardening recovery could be utilized to obtain enhanced mechanical properties of the material.

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Role of the α/β Interface in the Plastic Anisotropy of Single Colony Crystals in Titanium Alloys

MRS Proceedings ◽

10.1557/proc-819-n1.6 ◽

2004 ◽

Vol 819 ◽

Author(s):

M. F. Savage ◽

J. Tatalovich ◽

M. J. Mills

Keyword(s):

Orientation Relationship ◽

Basal Slip ◽

Plastic Anisotropy ◽

Slip Systems ◽

Transmission Mechanisms ◽

Single Colony ◽

Transmission Electron ◽

Strain Hardening Behavior ◽

Slip Transmission

AbstractThe anisotropy in room temperature plastic deformation has been investigated in single α(HCP)/β(BCC) colonies of a commercial α/β titanium alloy (Ti-6Al-2Sn-4Zr-2Mo-0.1Si) oriented for activation of individual basal slip systems. Detailed transmission electron microscopy (TEM) studies of the slip transmission mechanisms through the α/β interfaces have been performed to elucidate the role of these interfaces in determining yield and strain hardening behavior. Significant anisotropy in the yield strengths and hardening rates for the 3 unique basal slip systems is measured, and is attributed to the different slip transmission mechanisms active due to the near-Burgers orientation relationship existing between α- and β-phases. These results are should be transferable to other alloy systems exhibiting this orientation relationship.

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On the Metal Physical Considerations in the Machining of Metals

Journal of Engineering for Industry ◽

10.1115/1.3428342 ◽

1972 ◽

Vol 94 (4) ◽

pp. 1215-1224 ◽

Cited By ~ 8

Author(s):

S. Ramalingam ◽

J. T. Black

Keyword(s):

Plastic Deformation ◽

Strain Hardening ◽

Chip Formation ◽

Metal Cutting ◽

Dynamic Equilibrium ◽

Experimental Studies ◽

Second Phase ◽

Transmission Electron ◽

Second Phase Particles ◽

Strain Hardening Behavior

Experimental studies of plastic deformation produced during metal cutting have shown that a dynamic equilibrium is established between strain hardening and recovery during chip formation. Recrystallization studies on interrupted cut specimens show that the chip is formed by shear on a thin plane or surface which segments the chip into a lamella structure. Scanning and transmission electron microscopy studies on the lateral surfaces of prepolished interrupted cut specimens substantiate the evidence obtained from the recrystallization studies. The chip formation process has thus been found to be strongly sensitive to the metal physics and defect strticture of the material undergoing plastic deformation. The important variables involving dislocation interactions during chip formation are the number and orientation of operable slip systems, certain characteristic dislocation parameters such as stacking fault energy, the interaction of dislocations with vacancies and solute atoms or with second phase particles (both coherent and noncoherent types), the short and long range order of the material, and the temperature of the deformation, all of which affect the strain hardening behavior of the material. In addition, those factors which govern the kinetics of dynamic recovery such as outright collision of dislocation segments, cross slip, and climb induced by a supersaturation of point defects produced in the course of deformation must be considered.

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Differences in Deformation Behaviors Caused by Microband-Induced Plasticity of [0 0 1]- and [1 1 1]-Oriented Austenite Micro-Pillars

Metals ◽

10.3390/met11081179 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1179

Author(s):

Yuan-Yuan Cui ◽

Yun-Fei Jia ◽

Fu-Zhen Xuan

Keyword(s):

Strain Hardening ◽

Focused Ion Beam ◽

Ion Beam ◽

Uniaxial Compression Test ◽

Transmission Electron ◽

Scanning Transmission ◽

Deformation Behaviors ◽

Micro Pillars ◽

Strain Hardening Behavior ◽

Good Agreement

A uniaxial compression test and scanning/transmission electron microscopy observations were performed to investigate the differences in mechanical behavior and deformed microstructure between focused ion beam-manufactured [1 1 1]- and [0 0 1]-oriented austenite micro-pillars with 5 μm diameter from duplex stainless steel. After yielding, the strain hardening of two orientation micro-pillars increased sharply as a result of the formation of a microband, namely microband-induced plasticity, MBIP. The same phenomenon could be observed in a [0 0 1]-oriented pillar due to the activation of the secondary slip system, while slight strain hardening behavior was observed in the [1 1 1] orientation because of the refinement of the microband. Furthermore, the trend of the calculated strain hardening rates of both [1 1 1]- and [0 0 1]-oriented micro-pillars were in good agreement with the experimental data. This study proved that MBIP can be helpful for the mechanical property enhancement of steels.

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Observation of Dislocation Glide in Duplex Ti-48at.% Al after Room Temperature Tensile Deformation

MRS Proceedings ◽

10.1557/proc-1128-u04-04 ◽

2008 ◽

Vol 1128 ◽

Author(s):

Jörg M. K. Wiezorek ◽

Andreas K. Kulovits

Keyword(s):

Room Temperature ◽

Tensile Deformation ◽

Slip Systems ◽

Orientation Relation ◽

Dislocation Glide ◽

Dislocation Activity ◽

Pyramidal Slip ◽

Transmission Electron ◽

Pile Up ◽

Fully Lamellar

AbstractIn this study we investigated the deformation behavior of the hexagonal ordered phase α2- Ti3Al in Duplex TiAl under tensile loading. Transmission electron microscopy (TEM) revealed that the orientation relation ships (OR) between α2-Ti3Al and the L10 ordered γ- TiAl phase are very different as compared to the OR common in fully lamellar PST TiAl. We observed deformation related <2c+a> dislocation activity on pyramidal slip systems in the α2-phase during post situ TEM analyses. We rationalize this observation by the possible build up of pile up stresses in γ-TiAl due to the different OR with the α2-Ti3Al phase that can possibly lead to the activation of <2c+a> dislocation activity on pyramidal slip systems with similarly resolved stresses in the α2-Ti3Al phase.

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Effect of Initial Processing on the Microstructure-Property Relationships in Bake-Hardened C-Mn-Si TRIP Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.539-543.4315 ◽

2007 ◽

Vol 539-543 ◽

pp. 4315-4320 ◽

Cited By ~ 5

Author(s):

Ilana B. Timokhina ◽

Elena V. Pereloma ◽

Peter D. Hodgson

Keyword(s):

Strain Hardening ◽

Volume Fraction ◽

Bainitic Ferrite ◽

Tensile Tests ◽

Trip Steels ◽

Hardening Behavior ◽

Transmission Electron ◽

Before And After ◽

Initial Processing ◽

Strain Hardening Behavior

The effect of pre-straining (PS) and bake-hardening (BH) on the microstructure and mechanical properties has been studied in C-Mn-Si TRansformation Induced Plasticity (TRIP) steels after: (i) thermomechanically processing (TMP) and (ii) intercritical annealing. The steels were characterised before and after PS/BH by transmission electron microscopy (TEM), X-ray diffraction (XRD), and tensile tests. The main microstructural differences were the higher volume fraction of bainite and more stable retained austenite in the TMP steel. This led to a difference in the strain-hardening behavior before and after BH treatment. The higher dislocation density in ferrite and formation of microbands in the TMP steel after PS and the formation of Fe3C carbides between the bainitic ferrite laths during BH for both steels also affected the strain-hardening behavior. However, both steels after PS/BH treatment demonstrated an increase in the yield and tensile strength.

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Structure of stacking faults in pyrite using TEM techniques

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100122198 ◽

1992 ◽

Vol 50 (1) ◽

pp. 358-359

Author(s):

Raja Subramanian ◽

Kenneth S. Vecchio

Keyword(s):

Lattice Structure ◽

Stacking Faults ◽

Covalent Bond ◽

Group Symmetry ◽

Iron Pyrite ◽

Dislocation Glide ◽

Partial Dislocations ◽

Transmission Electron ◽

Contrast Analysis ◽

Chlorine Ions

The structure of stacking faults and partial dislocations in iron pyrite (FeS2) have been studied using transmission electron microscopy. Pyrite has the NaCl structure in which the sodium ions are replaced by iron and chlorine ions by covalently-bonded pairs of sulfur ions. These sulfur pairs are oriented along the <111> direction. This covalent bond between sulfur atoms is the strongest bond in pyrite with Pa3 space group symmetry. These sulfur pairs are believed to move as a whole during dislocation glide. The lattice structure across these stacking faults is of interest as the presence of these stacking faults has been preliminarily linked to a higher sulfur reactivity in pyrite. Conventional TEM contrast analysis and high resolution lattice imaging of the faulted area in the TEM specimen has been carried out.

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Quantitative energy-filtered tem imaging of interfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165173 ◽

1996 ◽

Vol 54 ◽

pp. 542-543 ◽

Cited By ~ 2

Author(s):

J. Bentley ◽

E. A. Kenik ◽

K. Siangchaew ◽

M. Libera

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Unit Volume ◽

Core Loss ◽

Mean Free Path ◽

Slit Width ◽

Elemental Mapping ◽

Low Loss ◽

Transmission Electron ◽

Inelastic Mean Free Path

Quantitative elemental mapping by inner shell core-loss energy-filtered transmission electron microscopy (TEM) with a Gatan Imaging Filter (GIF) interfaced to a Philips CM30 TEM operated with a LaB6 filament at 300 kV has been applied to interfaces in a range of materials. Typically, 15s exposures, slit width Δ = 30 eV, TEM magnifications ∼2000 to 5000×, and probe currents ≥200 nA, were used. Net core-loss maps were produced by AE−r background extrapolation from two pre-edge windows. Zero-loss I0 (Δ ≈ 5 eV) and “total” intensity IT (unfiltered, no slit) images were used to produce maps of t/λ = ln(IT/I0), where λ is the total inelastic mean free path. Core-loss images were corrected for diffraction contrast by normalization with low-loss images recorded with the same slit width, and for changes in thickness by normalization with t/λ, maps. Such corrected images have intensities proportional to the concentration in atoms per unit volume. Jump-ratio images (post-edge divided by pre-edge) were also produced. Spectrum lines across planar interfaces were recorded with TEM illumination by operating the GIF in the spectroscopy mode with an area-selecting slit oriented normal to the energy-dispersion direction. Planar interfaces were oriented normal to the area-selecting slit with a specimen rotation holder.

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