scholarly journals Analysis of the plastic deformation behavior for two austenitic NiCr-steels with different stacking fault energies

2018 ◽  
Vol 1 (1) ◽  
pp. 137-141
Author(s):  
Göran Engberg ◽  
Mikael Grehk ◽  
Karin Yvell
Keyword(s):  
Plastic Deformation ◽  
Dislocation Density ◽  
Tensile Tests ◽  
Stacking Fault ◽  
Size Distributions ◽  
Stress Strain ◽  
Free Distance ◽  
The Mean ◽  
Stacking Fault Energies

Two austenitic stainless steels, with low and medium stacking fault energies (SFE), 20 mJ/m2 and 30 mJ/m2 respectively, have been studied by conventional tensile tests and in situ tensile tests in a FEG-SEM equipped for EBSD. High angle boundaries (HAB) and low angle boundaries (LAB) with misorientations >= 10o and >= 2o respectively have been determined, and size distributions for the LABs have been derived by linear intercepts. It was found that the size distributions could be described by bimodal lognormal functions. For the steel with highest SFE plastic deformation took place by dislocation slip only while the steel with low SFE deformed by slip and twinning. Using a model for slip based on the evolution of the dislocation density with the generation of dislocations inversely proportional to the mean free distance of slip and recovery of dislocations proportional to the dislocation density the stress strain-curves were analyzed and the results compared with the measured quantities. The mean free distance of slip as evaluated from the stress-strain curve for the steel with the highest SFE correlates very well with the mean size of the LABs intercept. The rate of recovery also gave an expected stress dependence. The stress needed to start deformation twinning was based on the assumption that Shockley partials become completely separated in the slip plane. The thus calculated values for the twinning stress showed an excellent agreement with the observed start of twinning as given by EBSD evaluation of twin boundaries (TB). For the alloy with low SFE both surface grains (in situ test) and bulk grains (from interrupted conventional tests) were studied. The stress needed for slip and twinning of surface grains was, as expected, in the order of 0.5-0.6 times the applied stress.

Dislocation Density Effect on Thermal Diffusivity of AISI 316 Steel

2014 ◽  
Vol 605 ◽  
pp. 27-30 ◽  
Author(s):  
Girolamo Costanza ◽  
Roberto Montanari ◽  
Stefano Paoloni ◽  
Maria Elisa Tata
Keyword(s):  
Plastic Deformation ◽  
Thermal Diffusivity ◽  
Dislocation Density ◽  
Elastic Stress ◽  
Tensile Tests ◽  
Stress Fields ◽  
Scattering Mechanism ◽  
Dislocations Density ◽  
Aisi 316

AISI 316 steel samples have been investigated by infrared thermography (IRT) after introducing controlled degrees of plastic deformation by means of tensile tests. Microstructural examinations of the same samples showed that the progressive decrease of thermal diffusivity observed for successive steps of plastic deformation is due to the increase of dislocation density. Dislocations affect thermal diffusivity in two ways, by acting as centres of scattering and by inducing elastic stress fields. To evaluate the two contributions, IRT measurements have been also carried outin-situ,during tensile tests at progressively increasing strain. For relevant plastic deformation, the dislocations mainly affect the thermal diffusivity by scattering mechanism. On the basis of these results, it can be concluded that thermal diffusivity is significantly affected by the increase of dislocations density therefore locally resolved IRT measurements seem promising to detect states of local plasticization in mechanical components.

Influence of Severe Plastic Deformation on the PLC Effect and Mechanical Properties in Al 5XXX Alloy

2006 ◽  
Vol 114 ◽  
pp. 171-176 ◽  
Author(s):  
Joanna Zdunek ◽  
Pawel Widlicki ◽  
Halina Garbacz ◽  
Jaroslaw Mizera ◽  
Krzysztof Jan Kurzydlowski
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
True Strain ◽  
Tensile Tests ◽  
Size Reduction ◽  
Hydrostatic Extrusion ◽  
Stress Strain ◽  
Chatelier Effect

In this work, Al-Mg-Mn-Si alloy (5483) in the as-received and severe plastically deformed states was used. Plastic deformation was carried out by hydrostatic extrusion, and three different true strain values were applied 1.4, 2.8 and 3.8. All specimens were subjected to tensile tests and microhardness measurements. The investigated material revealed an instability during plastic deformation in the form of serration on the stress-strain curves, the so called Portevin-Le Chatelier effect It was shown that grain size reduction effected the character of the instability.

Introduction to Tensile Testing

2004 ◽  
pp. 1-12
Keyword(s):  
Plastic Deformation ◽  
Data Analysis ◽  
Uniaxial Tension ◽  
Tensile Testing ◽  
Tensile Tests ◽  
True Stress ◽  
Stress Strain ◽  
Engineering Applications ◽  
Test Methodology ◽  
Ultrasonic Techniques

Abstract Tensile tests are performed for several reasons. The results of tensile tests are used in selecting materials for engineering applications. Tensile properties often are used to predict the behavior of a material under forms of loading other than uniaxial tension. Elastic properties also may be of interest, but special techniques must be used to measure these properties during tensile testing, and more accurate measurements can be made by ultrasonic techniques. This chapter provides a brief overview of some of the more important topics associated with tensile testing. These include tensile specimens and test machines; stress-strain curves, including discussions of elastic versus plastic deformation, yield points, and ductility; true stress and strain; and test methodology and data analysis.

A New Correlation Between MC Precipitate Size, Aging Time and Temperature for an Advanced Austenitic Steel

1992 ◽  
Vol 114 (3) ◽  
pp. 364-368
Author(s):  
J. A. Todd ◽  
J. C. Ren
Keyword(s):  
Dislocation Density ◽  
Austenitic Steel ◽  
Aging Time ◽  
Cold Work ◽  
Precipitate Size ◽  
Size Distributions ◽  
New Correlation ◽  
Nucleation Sites ◽  
The Mean

The MC precipitate size distributions have been measured for times of 1, 10, 100, 300 and 1000 hr at 700 and 900° C in a 16Ni-14Cr advanced austenitic steel. A new correlation between the mean precipitate size, aging time and temperature has been developed. The new correlation is compatible with a solute exhaustion mechanism, which may explain why (i) the MC precipitates formed on matrix dislocations resist coarsening for up to 3000 hr at 900°C; and (ii) the degree of cold work (i.e., the dislocation density), which determines the number of MC nucleation sites, controls the limiting precipitate size.

scholarly journals Cyclic deformation leads to defect healing and strengthening of small-volume metal crystals

2015 ◽  
Vol 112 (44) ◽  
pp. 13502-13507 ◽  
Author(s):  
Zhang-Jie Wang ◽  
Qing-Jie Li ◽  
Yi-Nan Cui ◽  
Zhan-Li Liu ◽  
Evan Ma ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Cyclic Deformation ◽  
Cyclic Strain ◽  
Tensile Tests ◽  
Defect Engineering ◽  
Transmission Electron ◽  
Low Amplitude ◽  
Cyclic Straining ◽  
Accumulation Of Defects

When microscopic and macroscopic specimens of metals are subjected to cyclic loading, the creation, interaction, and accumulation of defects lead to damage, cracking, and failure. Here we demonstrate that when aluminum single crystals of submicrometer dimensions are subjected to low-amplitude cyclic deformation at room temperature, the density of preexisting dislocation lines and loops can be dramatically reduced with virtually no change of the overall sample geometry and essentially no permanent plastic strain. This “cyclic healing” of the metal crystal leads to significant strengthening through dramatic reductions in dislocation density, in distinct contrast to conventional cyclic strain hardening mechanisms arising from increases in dislocation density and interactions among defects in microcrystalline and macrocrystalline metals and alloys. Our real-time, in situ transmission electron microscopy observations of tensile tests reveal that pinned dislocation lines undergo shakedown during cyclic straining, with the extent of dislocation unpinning dependent on the amplitude, sequence, and number of strain cycles. Those unpinned mobile dislocations moving close enough to the free surface of the thin specimens as a result of such repeated straining are then further attracted to the surface by image forces that facilitate their egress from the crystal. These results point to a versatile pathway for controlled mechanical annealing and defect engineering in submicrometer-sized metal crystals, thereby obviating the need for thermal annealing or significant plastic deformation that could cause change in shape and/or dimensions of the specimen.

Constitutive Analyses of Tensile Tests on Pre-Rolled AA3003 Sheets

2014 ◽  
Vol 794-796 ◽  
pp. 710-715 ◽  
Author(s):  
Shigeo Saimoto ◽  
Kaan Inal ◽  
Hai Ou Jin
Keyword(s):  
Dislocation Density ◽  
Point Defects ◽  
Volume Fraction ◽  
Rolling Direction ◽  
Stage Iv ◽  
Tensile Tests ◽  
Internal Stresses ◽  
Thickness Strain ◽  
Stress Strain Relation ◽  
The Mean

A new rationale to assess the work-hardening locus for pre-rolled sheets is described based on the realization that since the internal stresses necessarily sum to zero, the mean dislocation density remains the same upon re-pull in the rolling direction. Thus the 0.2 % yield stress as function of thickness strains results in an estimate of the stress-strain relation during rolling. Under plane strain, the thickness strain is negative to that of extension and hence the deduced rolling locus is compared to that of extrapolated tensile one of the start sheet. This comparison indicates that the onset of Stage IV occurs when volume fraction of point defects produced attains about 2 %.

Ultrasonic in situ investigation of the initiation of Polyethylene's plastic deformation during tensile tests

Polymer ◽  
2017 ◽  
Vol 123 ◽  
pp. 258-266 ◽  
Author(s):  
N. Casiez ◽  
S. Deschanel ◽  
T. Monnier ◽  
O. Lame
Keyword(s):  
Plastic Deformation ◽  
Tensile Tests ◽  
In Situ Investigation

Micromechanical Tensile Testing

1996 ◽  
Vol 436 ◽  
Author(s):  
S. Greek ◽  
F. Ericson ◽  
S. Johansson ◽  
J.-Å. Schweitz
Keyword(s):  
Fracture Strength ◽  
Tensile Testing ◽  
Weibull Modulus ◽  
Tensile Tests ◽  
Cross Sectional ◽  
Weibull Statistics ◽  
Electrodeposited Nickel ◽  
The Mean ◽  
Scanning Electron

AbstractA method is described where tensile tests can be performed in situ on micromachined structures. The testing equipment consists of a testing unit mounted on a micromanipulator in a Scanning Electron Microscope (SEM). The fracture loads of micromachined beam structures made from thick and thin film polysilicon as well as from electrodeposited nickel and nickeliron alloy were measured, and the fracture strengths then calculated via measurements of the test structures’ initial cross-sectional areas. The statistical scatter of the polysilicon fracture strength values were evaluated by Weibull statistics. The mean fracture strength and the Weibull modulus, a measure of the scatter, were obtained

Dislocation study of ARMCO iron processed by ECAP

2016 ◽  
Vol 1818 ◽  
Author(s):  
Jairo Alberto Muñoz ◽  
Oscar Fabián Higuera ◽  
José María Cabrera
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Grain Size ◽  
Dislocation Density ◽  
Deformation Behavior ◽  
Armco Iron ◽  
Tensile Tests ◽  
Grain Sizes ◽  
Angular Pressing ◽  
Cylindrical Samples

ABSTRACTThe aim of this work was to study the deformation behavior of an Armco iron after severe plastic deformation by equal channel angular pressing (ECAP). Particular attention was paid to predict the dislocation density by different approaches like the model proposed by Bergström. Experimental measures of dislocation density by different techniques are used in the discussion. Cylindrical samples of ARMCO iron (8mm of diameter, 60mm of length) were subjected to ECAP deformation using a die with an intersecting channel of Φ=90° and outer arc of curvature of ψ= 37° die. Samples were deformed for up to 16 ECAP passes following route Bc. The mechanical properties of the material were measured after each pass by tensile tests. The original grain size of the annealed iron (70 μm) was drastically reduced after ECAP reaching grain sizes close to 300nm after 16 passes.

Sign in / Sign up

Export Citation Format

Share Document