scholarly journals Comparing In Situ DIC Results from an Etched Surface with a Gold Speckled Surface

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 820 ◽  
Author(s):  
Christian Oen Paulsen ◽  
Egil Fagerholt ◽  
Tore Børvik ◽  
Ida Westermann
Keyword(s):  
Gold Nanoparticles ◽  
Elevated Temperatures ◽  
Speckle Pattern ◽  
Local Strain ◽  
Image Correlation ◽  
Polished Surface ◽  
Two Phase ◽  
Continuous Layer ◽  
Etched Surface

A ferrite-pearlite two-phase steel was investigated using in situ scanning electron microscope (SEM) tensile testing combined with digital image correlation (DIC). Two different speckled patterns were used and compared. The first pattern was achieved by etching a polished surface in order to reveal the microstructural features. Second, a gold speckled pattern was obtained. Here, a continuous layer of gold was applied to a polished surface. This continuous layer was remodeled into gold nanoparticles by keeping the specimen at 180 °C for 96 h with an Ar/Styrene mixture flowing across the specimen surface. The result is randomly distributed gold nanoparticles on the surface. These particles and the etched microstructure were then used by the DIC software to correlate an image series to obtain the local strain field of the material. The differences between the two techniques are numerous. Considering the etched surface, most microstructural features were grain boundaries and pearlite lamellas. As a consequence, large areas within grains did not provide sufficient contrast for DIC, thus restricting maximum resolution. However, the technique is fast and does not expose the material to any elevated temperatures. In contrast, the gold remodeling method provides a finely dispersed gold speckle pattern on the surface, giving excellent contrast across the recorded area. DIC with gold particles achieved a spatial resolution of 0.096 µm, compared to 2.24 µm in the DIC for the etched specimen. As a result, DIC with gold speckles can resolve slip lines. Conversely, DIC with etched microstructure resolves local strains on grain level. However, it is less cumbersome and faster to perform the test on the etched specimen.

scholarly journals Effect of the gold remodeling preparation method on the microstructure and mechanical behavior of steel

2020 ◽  
Vol 2 (10) ◽  
Author(s):  
Christian Oen Paulsen ◽  
Tore Børvik ◽  
Ida Westermann
Keyword(s):  
Elevated Temperatures ◽  
Preparation Method ◽  
Tensile Behavior ◽  
Image Correlation ◽  
Polished Surface ◽  
Dual Phase ◽  
Sem Images ◽  
Dp Steel ◽  
Successful Technique

Abstract The application of gold speckles on a polished surface is a successful technique for improving digital image correlation (DIC) contrast in scanning electron microscope (SEM) images. In the process of creating the gold speckles, the material is subjected to elevated temperatures for prolonged times. As a consequence, not all materials are suitable for the gold speckled method to improve the contrast for DIC measurements during an in-situ SEM tensile test. In this letter, the effect of gold remodeling on two different steels is investigated. These steels are a dual-phase (DP) steel and a ferrite–pearlite steel (NVE36). The results demonstrate that the temperature these steels are subjected to during gold remodeling will influence the tensile behavior of the DP steel while the NVE36 steel is unaffected by the heat treatment. As a result, we can conclude that the gold remodeling method for creating contrast in SEM images may affect the microstructure. However, the effect of these changes depends on the material at hand and will vary from material to material.

scholarly journals Thermal stability of retained austenite in bainitic steel: an  in situ study

2011 ◽  
Vol 467 (2135) ◽  
pp. 3141-3156 ◽  
Author(s):  
A. Saha Podder ◽  
I. Lonardelli ◽  
A. Molinari ◽  
H. K. D. H. Bhadeshia
Keyword(s):  
Martensitic Transformation ◽  
Retained Austenite ◽  
Elevated Temperatures ◽  
Bainitic Ferrite ◽  
Ambient Conditions ◽  
Two Phase ◽  
Tempering Temperature ◽  
Thermal Stability Of ◽  
Lower Carbon

The tempering of two-phase mixtures of bainitic ferrite and carbon-enriched retained austenite has been investigated in an effort to separate the reactions that occur at elevated temperatures from any transformation during cooling to ambient conditions. It is demonstrated using synchrotron X-radiation measurements that the residue of austenite left at the tempering temperature partly decomposes by martensitic transformation when the sample is cooled. It is well established in the published literature that films of retained austenite are better able to resist stress or strain-induced martensitic transformation than any coarser particles of austenite. In contrast, the coarser austenite is more resistant to the precipitation of cementite during tempering than the film form because of its lower carbon concentration.

Microstructures and Mechanical Properties of NiAl+Mo In-Situ Eutectic Composites

1990 ◽  
Vol 194 ◽  
Author(s):  
P. R. Subramanian ◽  
M. G. Mendiratta ◽  
D. B. Miracle ◽  
D. M. Dimiduk
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Room Temperature ◽  
Composite System ◽  
Elevated Temperatures ◽  
Two Phase ◽  
Structural Applications ◽  
Temperature Fracture

AbstractThe quasibinary NiAI-Mo system exhibits a large two-phase field between NiAl and the terminal (Mo) solid solution, and offers the potential for producing in-situ eutectic composites for high-temperature structural applications. The phase stability of this composite system was experimentally evaluated, following long-term exposures at elevated temperatures. Bend strengths as a function of temperature and room-temperature fracture toughness data are presented for selected NiA1-Mo alloys, together with results from fractography observations.

Local Strain Imaging during Mechanical Loading of Lamellar Microstructures in Titanium Based Alloys

2004 ◽  
Vol 1-2 ◽  
pp. 159-164
Author(s):  
L. Babout ◽  
J. Quinta Da Fonseca ◽  
Michael Preuss
Keyword(s):  
Tensile Testing ◽  
Lamellar Microstructure ◽  
Local Strain ◽  
Boundary Region ◽  
Electron Back Scatter Diffraction ◽  
Surface Strain ◽  
Image Correlation ◽  
Fully Lamellar ◽  
Optical Micrographs

In this work optical microscopy in situ tensile testing has been carried out to study the localisation of surface strain in fully lamellar titanium alloys. The localised strain was measured by analysing the recorded optical micrographs using image correlation, and the orientation of the a lamellae colony was determined by using Electron Back Scatter Diffraction (EBSD). The results show a localisation of strain, which seems to depend on the crystallographic orientation of the a lamellae colony in the lamellar microstructure. No significant strain was observed in the former b grain boundary region.

One-pot synthesis with in situ preconcentration of spherical monodispersed gold nanoparticles using thermoresponsive 3-(alkyldimethylammonio)-propyl sulfate zwitterionic surfactants

2016 ◽  
Vol 52 (65) ◽  
pp. 10000-10003 ◽  
Author(s):  
Yoshitaka Takagai ◽  
Ryo Miura ◽  
Arata Endo ◽  
Willie L. Hinze
Keyword(s):  
Gold Nanoparticles ◽  
Elevated Temperatures ◽  
Reduction Method ◽  
One Pot ◽  
Homogeneous Solutions ◽  
Zwitterionic Surfactants ◽  
One Pot Synthesis ◽  
Citrate Reduction ◽  
In Situ Preconcentration

Homogeneous solutions of thermoresponsive zwitterionic 3-(alkyldimethylammonio)-propyl sulfate surfactants at elevated temperatures were employed for the synthesis of gold nanoparticles (AuNPs) by the citrate reduction method.

A Full-Field Stress Based Damage Assessment Approach for In Situ Inspection of Composite Structures

2013 ◽  
Vol 569-570 ◽  
pp. 3-10 ◽  
Author(s):  
Janice M. Dulieu-Barton ◽  
R.K. Fruehmann ◽  
Simon Quinn
Keyword(s):  
Composite Structures ◽  
Speckle Pattern ◽  
Stress Raiser ◽  
Thermoelastic Stress ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Inspection Method ◽  
Full Field ◽  
Distribution Of Stresses

This paper describes the development of a stress / strain based in-situ damage inspection strategy focused around, but not exclusively, using thermoelastic stress analysis (TSA). The underlying philosophy is that defects and damage in a component or structure only constitute a cause for concern if these influence the stress field, i.e. the defect or damage acts as a stress raiser that reduces the service load limit. To assess this, it is necessary for the inspection method to map the distribution of stresses in the component, rather than the location and extent of an irregularity in the material. Imaging based techniques, such as TSA, digital image correlation (DIC) or digital speckle pattern interferometry (DSPI) provide non-contact maps of the surface stresses, deformations and/or strains. The full field data enables the engineer to evaluate if stress concentrations are present within the structure and, if data from a previous inspection is available, to assess if the distribution of stresses within the structure has changed from a previous 'undamaged' state. One of the key issues addressed in the current work has been the transition from a standard test setup, as typically used in laboratory work, to a more flexible (portable) setup relevant to industry requirements, e.g. site inspections. An approach that enables similar resolution (by comparison to current laboratory standard setups) stress and strain data to be captured using natural frequency excitation of a structure has been demonstrated on various full scale components.

3D/4D Strain Mapping Using In Situ X-Ray Microtomography

2011 ◽  
Vol 70 ◽  
pp. 249-254 ◽  
Author(s):  
Hiroyuki Toda ◽  
Kentaro Uesugi ◽  
Yoshio Suzuki ◽  
Masakazu Kobayashi
Keyword(s):  
Strain Distribution ◽  
Crack Tip ◽  
Local Strain ◽  
Image Correlation ◽  
Correlation Technique ◽  
In Situ Observation ◽  
Strain Mapping ◽  
X Ray ◽  
Discrete Crack

X-ray microtomography (XMT) has been utilized for the in-situ observation of various structural materials under external disturbance such as loading. In-situ XMT provides a unique possibility to access the three-dimensional (3D) character of internal microstructure and its time evolution behaviours non-destructively, thereby enabling advanced techniques for measuring local strain distribution. Local strain mapping is readily enabled by processing such high-resolution tomographic images either by the particle tracking technique or the digital image correlation technique. Procedures for tracking microstructural features which have been developed by the authors, have been applied to analyse localised deformation and damage evolution in a material. Typically several tens of thousands of microstructural features, such as particles and pores, are tracked in a tomographic specimen (0.2 - 0.3 mm3in volume). When a sufficient number of microstructural features is dispersed in 3D space, the Delaunay tessellation algorithm is used to obtain local strain distribution. With these techniques, 3D strain fields can be measured with reasonable accuracy. Even local crack driving forces, such as local variations in the stress intensity factor, crack tip opening displacement and J integral along a crack front line, can be measured from discrete crack tip displacement fields.

Dependence of small-angle neutron scattering contrast on the difference in thermal expansions of phases in two-phase alloys

2009 ◽  
Vol 42 (6) ◽  
pp. 981-989 ◽  
Author(s):  
Pavel Strunz ◽  
Ralph Gilles ◽  
Debashis Mukherji ◽  
Michael Hofmann ◽  
Dominique del Genovese ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Elevated Temperatures ◽  
Base Alloy ◽  
Integral Intensity ◽  
Two Phase ◽  
The Difference ◽  
The Individual

Theoretical expressions describing small-angle neutron scattering (SANS) contrast dependence on temperature in the region where no phase-composition changes occur were derived for two-phase Ni superalloys. The theory is based on the difference in thermal expansion of the two primary phases, γ and γ′. The simulations show that the scattering contrast temperature evolution is significant enough to be considered inin situSANS experiments with superalloys at elevated temperatures. The simulations performed show that the magnitude of the scattering contrast at room temperature is firmly connected with the particular shape of the scattering contrast temperature dependence. This fact can be used for determination of the scattering contrast without a knowledge of the compositions of the individual phases. The theoretical expressions derived for scattering contrast were proven experimentally on an Ni–Fe-base alloy, DT706. The evolution of lattice parameters of both the matrix and the precipitate phases was obtained from anin situwide-angle neutron diffraction experiment. The theoretical scattering contrast dependence was then successfully fitted to the measured SANS integral intensity.

Electron and ion irradiation-induced dissolution of mechanical twins in the intermetalic U3Si: An in situ HVEM study

1989 ◽  
Vol 47 ◽  
pp. 652-653
Author(s):  
Charles W. Allen ◽  
Robert C. Birtcher
Keyword(s):  
Elevated Temperatures ◽  
Ion Irradiation ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Heavy Ion ◽  
High Energy ◽  
Mechanical Twinning ◽  
In Situ Experiments

The uranium silicides, including U3Si, are under study as candidate low enrichment nuclear fuels. Ion beam simulations of the in-reactor behavior of such materials are performed because a similar damage structure can be produced in hours by energetic heavy ions which requires years in actual reactor tests. This contribution treats one aspect of the microstructural behavior of U3Si under high energy electron irradiation and low dose energetic heavy ion irradiation and is based on in situ experiments, performed at the HVEM-Tandem User Facility at Argonne National Laboratory. This Facility interfaces a 2 MV Tandem ion accelerator and a 0.6 MV ion implanter to a 1.2 MeV AEI high voltage electron microscope, which allows a wide variety of in situ ion beam experiments to be performed with simultaneous irradiation and electron microscopy or diffraction.At elevated temperatures, U3Si exhibits the ordered AuCu3 structure. On cooling below 1058 K, the intermetallic transforms, evidently martensitically, to a body-centered tetragonal structure (alternatively, the structure may be described as face-centered tetragonal, which would be fcc except for a 1 pet tetragonal distortion). Mechanical twinning accompanies the transformation; however, diferences between electron diffraction patterns from twinned and non-twinned martensite plates could not be distinguished.

The threshold energy for atom displacement in fcc metals

1990 ◽  
Vol 48 (4) ◽  
pp. 530-531
Author(s):  
Wilfried Sigle ◽  
Matthias Hohenstein ◽  
Alfred Seeger
Keyword(s):  
Growth Rate ◽  
Elevated Temperatures ◽  
Threshold Energy ◽  
Dislocation Loops ◽  
Absolute Minimum ◽  
Voltage Electron ◽  
Atom Displacement ◽  
Electron Microscopes ◽  
Fcc Metal

Prolonged electron irradiation of metals at elevated temperatures usually leads to the formation of large interstitial-type dislocation loops. The growth rate of the loops is proportional to the total cross-section for atom displacement,which is implicitly connected with the threshold energy for atom displacement, Ed . Thus, by measuring the growth rate as a function of the electron energy and the orientation of the specimen with respect to the electron beam, the anisotropy of Ed can be determined rather precisely. We have performed such experiments in situ in high-voltage electron microscopes on Ag and Au at 473K as a function of the orientation and on Au as a function of temperature at several fixed orientations.Whereas in Ag minima of Ed are found close to <100>,<110>, and <210> (13-18eV), (Fig.1) atom displacement in Au requires least energy along <100>(15-19eV) (Fig.2). Au is thus the first fcc metal in which the absolute minimum of the threshold energy has been established not to lie in or close to the <110> direction.

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