A new analysis of yielding and work hardening in AA1100 and AA5754 at low temperatures

2012 ◽  
Vol 60 (18) ◽  
pp. 6352-6361 ◽  
Author(s):  
Shigeo Saimoto ◽  
David J. Lloyd
Keyword(s):  
Work Hardening ◽  
Low Temperatures

Deformation Mechanisms in High-Al Bearing High-Mn TWIP Steels in Hot Compression and in Tension at Low Temperatures

2007 ◽  
Vol 550 ◽  
pp. 217-222 ◽  
Author(s):  
Atef S. Hamada ◽  
L. Pentti Karjalainen ◽  
Mahesh C. Somani ◽  
R.M. Ramadan
Keyword(s):  
Austenitic Steel ◽  
Work Hardening ◽  
Hot Deformation ◽  
Low Temperatures ◽  
Deformation Behaviour ◽  
Tensile Tests ◽  
Mechanical Twinning ◽  
Al Content ◽  
Duplex Steel ◽  
Twip Steels

The hot deformation behaviour of two high-Mn (23-24 wt-%) TWIP steels containing 6 and 8 wt-% Al with the fully austenitic and duplex microstructures, respectively, has been investigated at temperatures of 900-1100°C. In addition, tensile properties were determined over the temperature range from -80 to 100°C. It was observed that in spite of the lower Al content, the austenitic steel possessed the hot deformation resistance about twice as high as that of the duplex steel. Whereas the flow stress curves of the austenitic steel exhibited work hardening followed by slight softening due to dynamic recrystallisation, the duplex steel showed the absence of work hardening and discontinuous yielding under similar conditions. Tensile tests at low temperatures revealed that the austenitic grade had a lower yield strength than that of the duplex grade, but much better ductility, the elongation increasing with decreasing temperature, contrary to that for the duplex steel. This can be attributed to the intense mechanical twinning in the austenitic steel, while in the duplex steel, twinning occurred in the ferrite only and the austenite showed dislocation glide.

Staged work hardening of polycrystalline titanium at low temperatures and its relation to substructure evolution

2002 ◽  
Vol 28 (12) ◽  
pp. 935-941 ◽  
Author(s):  
V. A. Moskalenko ◽  
A. R. Smirnov ◽  
V. N. Kovaleva ◽  
V. D. Natsik
Keyword(s):  
Work Hardening ◽  
Low Temperatures

The Mechanism of Work-hardening of Metals

1952 ◽  
Vol 166 (1) ◽  
pp. 413-418 ◽  
Author(s):  
N. F. Mott
Keyword(s):  
Work Hardening ◽  
Slip Line ◽  
Low Temperatures ◽  
Lattice Site ◽  
Dislocation Line ◽  
Slip Lines ◽  
Slip Bands ◽  
Cold Worked ◽  
Internal Strains ◽  
Full Height

The most striking feature of the deformation of metals is the formation of slip lines. Recent investigations suggest that, when formed at low temperatures, each slip line is the result of a displacement of the material along a single lattice plane through a distance of about a thousand atomic diameters. Moreover, there is much evidence that the steps on the surface which appear as slip bands attain their full height in a small fraction of a second, though their length may thereafter increase slowly. At higher temperatures and at slow rates of strain the slip bands appear, under the electron microscope, as clusters of lines about a hundred atomic diameters apart. The origin of slip lines, the reason for this clustering and the cause of work-hardening are discussed. The two conceptions used in the discussion are the dislocation line and the vacant lattice site. Slip lines are believed to have their origin in a certain arrangement of dislocation lines of frequent occurrence in the interior of the crystal. These are known as Frank-Read sources; their relation to recent work on the growth of crystals is shown. Where a slip line terminates dislocations must remain in the crystal; to the internal strains round these is ascribed work-hardening, much as in Taylor's theory of 1934†. It is now, however, possible to explain what it is that stabilizes the dislocations and prevents them from moving back when the stress is released. Finally, vacant lattice sites are shown to be formed in a cold-worked material. If the temperature is high enough for them to diffuse, they soften the material round the slip band and allow the observed clusters to form. They also play a part in producing the observed “fragmentation” of cold-worked material.

Mechanical Stability and Deformation-Induced Transformation of Retained Austenite in TRIP Steels at Low Temperatures

2017 ◽  
Vol 741 ◽  
pp. 36-41 ◽  
Author(s):  
Takayuki Yamashita ◽  
Norimitsu Koga ◽  
Osamu Umezawa
Keyword(s):  
Low Temperature ◽  
Work Hardening ◽  
Low Temperatures ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
High Strain ◽  
Volume Fraction ◽  
Trip Steels ◽  
The Stability ◽  
Strength And Ductility

The tensile properties and the stability of retained austenite in TRIP steels with different volume fraction of retained austenite have been studied at low temperature. The steels showed a good valance of strength and ductility at 193 K. Their work-hardening rates were decreased linearly and kept a high value in the high strain regime at 193 K. The retained austenite was mostly transformed into martensite less than 10% strain at 193 K.

Interpretation of irradiation-induced changes in electron diffractograms and images of extinction contours at low temperatures

1984 ◽  
Vol 42 ◽  
pp. 268-269
Author(s):  
E. Knapek ◽  
H. Formanek ◽  
G. Lefranc ◽  
I. Dietrich
Keyword(s):  
Low Temperatures ◽  
Carbon Films ◽  
Organic Crystals ◽  
Wide Spread ◽  
Lens System ◽  
Preparation Conditions ◽  
Thin Carbon ◽  
Electron Diffractograms ◽  
Diffraction Patterns ◽  
Induced Changes

A few years ago results on cryoprotection of L-valine were reported, where the values of the critical fluence De i.e, the electron exposure which decreases the intensity of the diffraction reflections by a factor e, amounted to the order of 2000 + 1000 e/nm2. In the meantime a discrepancy arose, since several groups published De values between 100 e/nm2 and 1200 e/nm2 /1 - 4/. This disagreement and particularly the wide spread of the results induced us to investigate more thoroughly the behaviour of organic crystals at very low temperatures during electron irradiation.For this purpose large L-valine crystals with homogenuous thickness were deposited on holey carbon films, thin carbon films or Au-coated holey carbon films. These specimens were cooled down to nearly liquid helium temperature in an electron microscope with a superconducting lens system and irradiated with 200 keU-electrons. The progress of radiation damage under different preparation conditions has been observed with series of electron diffraction patterns and direct images of extinction contours.

Radiation Damage of Support Films

1981 ◽  
Vol 39 ◽  
pp. 28-29
Author(s):  
H.A. Cohen ◽  
W. Chiu
Keyword(s):  
Transfer Function ◽  
Low Temperatures ◽  
Carbon Support ◽  
Contrast Transfer Function ◽  
Electron Dose ◽  
Imaging Parameters ◽  
Negative Stain ◽  
Phase Corrections ◽  
Two Parameters ◽  
Medium Dose

The goal of imaging the finest detail possible in biological specimens leads to contradictory requirements for the choice of an electron dose. The dose should be as low as possible to minimize object damage, yet as high as possible to optimize image statistics. For specimens that are protected by low temperatures or for which the low resolution associated with negative stain is acceptable, the first condition may be partially relaxed, allowing the use of (for example) 6 to 10 e/Å2. However, this medium dose is marginal for obtaining the contrast transfer function (CTF) of the microscope, which is necessary to allow phase corrections to the image. We have explored two parameters that affect the CTF under medium dose conditions.Figure 1 displays the CTF for carbon (C, row 1) and triafol plus carbon (T+C, row 2). For any column, the images to which the CTF correspond were from a carbon covered hole (C) and the adjacent triafol plus carbon support film (T+C), both recorded on the same micrograph; therefore the imaging parameters of defocus, illumination angle, and electron statistics were identical.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

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