scholarly journals Time-Resolved Neutron Bragg-Edge Imaging: A Case Study by Observing Martensitic Phase Formation in Low Temperature Transformation (LTT) Steel during GTAW

2021 ◽  
Vol 11 (22) ◽  
pp. 10886
Author(s):  
Axel Griesche ◽  
Beate Pfretzschner ◽  
Ugur Alp Taparli ◽  
Nikolay Kardjilov
Keyword(s):  
Waller Factor ◽  
Neutron Imaging ◽  
Martensitic Phase ◽  
Steel Plates ◽  
Full Spectrum ◽  
Austenitic Phase ◽  
Time Resolved ◽  
Neutron Transmission ◽  
Monochromatic Imaging ◽  
Gas Tungsten Arc

Polychromatic and wavelength-selective neutron transmission radiography were applied during bead-on-plate welding on 5 mm thick sheets on the face side of martensitic low transformation temperature (LTT) steel plates using gas tungsten arc welding (GTAW). The in situ visualization of austenitization upon welding and subsequent α’-martensite formation during cooling could be achieved with a temporal resolution of 2 s for monochromatic imaging using a single neutron wavelength and of 0.5 s for polychromatic imaging using the full spectrum of the beam (white beam). The spatial resolution achieved in the experiments was approximately 200 µm. The transmitted monochromatic neutron beam intensity at a wavelength of λ = 0.395 nm was significantly reduced during cooling below the martensitic start temperature Ms since the emerging martensitic phase has a ~10% higher attenuation coefficient than the austenitic phase. Neutron imaging was significantly influenced by coherent neutron scattering caused by the thermal motion of the crystal lattice (Debye–Waller factor), resulting in a reduction in the neutron transmission by approx. 15% for monochromatic and by approx. 4% for polychromatic imaging.

In Situ Measurement of Poisson’s Ratio of Steel Plates During Thermal Processes Using Resonant Modes

2021 ◽  
Author(s):  
Clemens Grünsteidl ◽  
Christian Kerschbaummayr ◽  
Edgar Scherleitner ◽  
Bernhard Reitinger ◽  
Georg Watzl ◽  
...  
Keyword(s):  
Poisson’S Ratio ◽  
Dual Phase Steel ◽  
Steel Plates ◽  
Poisson's Ratio ◽  
Austenitic Phase ◽  
Resonant Modes ◽  
Longitudinal Sound Velocity ◽  
Contact Free

Abstract We demonstrate the determination of the Poisson’s ratio of steel plates during thermal processing based on contact free laser ultrasound measurements. Our method utilizes resonant elastic waves sustained by the plate, provides high amplitudes, and requires only a moderate detection bandwidth. For the analysis, the thickness of the samples does not need to be known. The trend of the measured Poisson’s ratio reveals a phase transformation in dual-phase steel samples. While previous approaches based on the measurement of the longitudinal sound velocity cannot distinguish between the ferritic and austenitic phase above 770°C, the shown method can. If the thickness of the samples is known, the method also provides both sound velocities of the material. The gained complementary information could be used to analyze phase composition of steel from low temperatures up to its melting point.

Biomolecular dynamics: A report from a workshop in Gysinge, Sweden, October 4–7, 1982

1984 ◽  
Vol 17 (2) ◽  
pp. 125-151 ◽  
Author(s):  
Olle Edholm ◽  
Lennart Nilsson ◽  
Otto Berg ◽  
Måns Ehrenberg ◽  
Flora Claesens ◽  
...  
Keyword(s):  
Waller Factor ◽  
Biological Macromolecules ◽  
Time Resolved ◽  
X Ray Crystallography ◽  
Biomolecular Dynamics ◽  
Debye Waller Factor ◽  
Membrane Components ◽  
Theoretical Simulations ◽  
Structure Of Proteins ◽  
Molecular Picture

From the results of X-ray crystallography a wealth of information is now available concerning the detailed molecular structure of proteins, nucleic acids, and membrane components. This has made it possible to apply successfully various spectroscopie techniques for time resolved studies as well as theoretical simulations of internal molecular dynamics in the biological macromolecules and molecular aggregates. We were particularly pleased to see professor Ivar Waller among the participants of the workshop since new use of the wellknown Debye–Waller factor has greatly contributed to this development. A molecular picture is presently emerging including the dimension of time which ultimately will give us a detailed understanding of the functional interactions between biomolecules in general, and in particular enzyme catalysis, nucleic acid functions, and transport of matter and information through membranes.

A Combinatorial Study for Interdiffusion, Crystallography and Mechanical Behavior of Ni-Mn-Ga Alloys

2017 ◽  
Vol 371 ◽  
pp. 153-159 ◽  
Author(s):  
Le Zhou ◽  
Anit Giri ◽  
Kyu Cho ◽  
Yong Ho Sohn
Keyword(s):  
Electron Microscopy ◽  
Martensitic Transformation ◽  
Interphase Boundary ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Sharp Decrease ◽  
Martensitic Phase ◽  
Diffusion Couples ◽  
Austenitic Phase ◽  
Solid Diffusion

The ferromagnetic shape memory and magnetocaloric properties of NiMnGa alloys are closely related to the martensitic transformation from high temperature austenitic phase to low temperature martensitic phase. The transformation temperature and the resulting microstructure and crystallography of the martensites can be very complex, but are crucial to the optimization of the material performance. A combinatorial study with a series of solid-to-solid diffusion couples and various characterization techniques, including scanning electron microscopy, focused ion beam, transmission electron microscopy, electron probe microanalysis, and nanoindentation, was carried out to investigate the microstructural and crystallographic development, and mechanical properties in NiMnGa alloys. Both austenitic and martensitic phases were found at room temperature in each diffusion couple with a clear interphase boundary. Crystallographic variations in martensitic phase, including non-modulated (NM) martensite and modulated (5M or 7M) martensite, were found in the diffusion couples. All martensitic microstructure consists of variants with different orientations and the twinning relationship. A decrease of reduced elastic modulus (Er) was observed with Ni substituting for Ga in the austenitic phase. However, an opposite trend of an increase in Er was found in the martensitic phase. The softening of the elastic constants near the vicinity of martensitic transformation contributed to a sharp decrease in Er near the interphase boundary. The measured Er had a larger scatter for the martensitic phase than that for the austenitic phase.

Elevated Temperature Properties of Maraging Steel Plates and Welds

1971 ◽  
Vol 93 (2) ◽  
pp. 218-224
Author(s):  
N. Kenyon ◽  
E. P. Sadowski ◽  
P. P. Hydrean
Keyword(s):  
Elevated Temperature ◽  
Maraging Steel ◽  
Elevated Temperatures ◽  
High Strength Steels ◽  
High Strength ◽  
Steel Plates ◽  
Maraging Steels ◽  
Gas Tungsten Arc ◽  
Temperature Exposure ◽  
Rupture Behavior

The creep rupture behavior, and the effects of elevated temperature exposure in air and hydrogen on the subsequent room temperature properties of a 12 percent Ni-5 percent Cr-3 percent Mo maraging steel are described. Tests have been made on several heats of plate and on gas tungsten-arc, gas metal-arc, and electroslag welds. On the basis of the results obtained, maraging steels offer promise as high-strength steels for service at elevated temperatures.

Study of the Effect of Active Fluxes in Gas Tungsten Arc Welding

2011 ◽  
Vol 189-193 ◽  
pp. 3579-3582
Author(s):  
Jian Hao ◽  
Zhen Luo ◽  
Xian Zheng Bu ◽  
Jian Wu Zhang
Keyword(s):  
Stainless Steel ◽  
Thin Layer ◽  
Arc Welding ◽  
Gas Tungsten Arc Welding ◽  
Steel Plates ◽  
Angular Distortion ◽  
Deep Penetration ◽  
Weld Penetration ◽  
Gas Tungsten Arc ◽  
Gas Tungsten

In order to investigate the effect of active fluxes on weld penetration, angular distortion and weld morphology in gas tungsten arc welding (GTAW), three types of oxide fluxes-CaO, TiO2and Al2O3-were used in the welding of 5mm think stainless steel plates. Those powders were applied through a thin layer of the flux to produce a bead on plate welds. The results showed that compared with conventional TIG welding, increased weld penetration and reduced angular distortion of the weld piece were obtained with the application of active fluxes. However, the weld morphology was not changed significantly when the powders were coated on the surface of steel. It was also found that each of the powders has a fittest range in penetration increment. Whether the rate of the coating run out of the range, the effects of these active fluxes on the increased weld penetration were not obvious. The CaO flux has a narrow effective range for deep penetration, while the Al2O3powder does have no effect on A-TIG penetration. The mechanism of those different performances has not been found out. According to the investment, the mechanism of active fluxes for the increased weld penetration and reduced angular distortion is related to the contraction of the arc.

In Situ Tensile Deformation of TRIP Steel / Mg-PSZ Composites

2013 ◽  
Vol 738-739 ◽  
pp. 77-81 ◽  
Author(s):  
Anja Weidner ◽  
Harry Berek ◽  
Christian Segel ◽  
Christos G. Aneziris ◽  
Horst Biermann
Keyword(s):  
Phase Transformation ◽  
Tensile Deformation ◽  
Electron Backscatter Diffraction ◽  
Deformation Energy ◽  
Martensitic Phase ◽  
Martensitic Phase Transformation ◽  
Steel Matrix ◽  
Austenitic Phase ◽  
Martensitic Phase Transformations

Composite material on the basis of a TRIP (transformation induced plasticity) steel with zirconia particles as reinforcement was produced by powder metallurgical technology and conventional sinter process. The goal of such type of material is to obtain exceptional mechanical properties like high deformation energy absorption due to the combination of martensitic phase transformations both in steel and ceramic. The steel matrix was made of the commercial steel AISI 304, which shows a deformation-induced martensitic phase transformation from the austenitic phase (fcc) into the α’-martensite (bcc). The zirconia particles were partially stabilized with MgO and show a stress-assisted martensitic phase transformation from the tetragonal to the monocline phase. Flat specimens were tensile deformed in-situ in a scanning electron microscope in order to follow the damage behaviour of the material. Some zirconia particles were characterized before and after tensile testing both by backscattered electron contrast as well as by electron backscatter diffraction (EBSD) in combination with energy dispersive X-ray spectroscopy (EDS).

scholarly journals 3D Isotope Density Measurements by Energy-Resolved Neutron Imaging

2021 ◽  
Author(s):  
Adrian Simon Losko ◽  
Sven Vogel
Keyword(s):  
Cross Sections ◽  
Nuclear Physics ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
Neutron Imaging ◽  
X Rays ◽  
Neutron Transmission ◽  
Quantitative Measurements ◽  
Transmission Detector ◽  
Elemental Characterization

Abstract Tools for three-dimensional elemental characterization are available on length scales ranging from individual atoms, using electrons as a probe, to micrometers with X-rays. However, for larger volumes up to millimeters or centimeters, quantitative measurements of elemental or isotope densities were hitherto only possible on the surface. Here, a novel quantitative elemental characterization method based on energy-resolved neutron imaging, utilizing the known neutron absorption cross sections with their ‘finger-print’ absorption resonance signatures, is demonstrated. Enabled by a pixilated time-of-flight neutron transmission detector installed at an intense short-pulsed spallation neutron source, for this demonstration 3.25 million state-of-the-art nuclear physics neutron transmission analyses were conducted to derive isotopic densities for five isotopes in 3D in a volume of 0.25 cm3. The tomographic reconstruction of the isotope densities provides elemental maps similar to X-ray microprobe maps for any cross-section in the probed volume. The bulk isotopic density of a U-20Pu-10Zr-3Np-2Am nuclear transmutation fuel sample was measured, agrees well with mass-spectrometry and is evidence of the accuracy of the method.

scholarly journals Finite element approach to Bragg edge neutron strain tomography

2020 ◽  
Vol 60 ◽  
Author(s):  
Riya Aggarwal ◽  
Mike Meylan ◽  
Bishnu Lamichhane ◽  
Chris Wensrich
Keyword(s):  
Machine Learning ◽  
Finite Element Method ◽  
Finite Element ◽  
Gaussian Processes ◽  
Elastic Strain ◽  
Neutron Imaging ◽  
The Finite Element Method ◽  
Neutron Transmission ◽  
Ray Transform ◽  
Element Method

A number of techniques and applications in neutron imaging that exploit wavelength resolved measurements have been developed recently. One such technique, known as energy resolved neutron imaging, receives ample attention because of its capability to not only visualise but to also quantify physical attributes with spatial resolution. The objective of this article is to develop a reconstruction algorithm for elastic strain tomography from Bragg edge neutron transmission strain images obtained from a pulsed neutron beam with high resolution. This technique has several advantages over those using monochromatic neutron beams from continuous sources; for example, finer wavelength resolution. In contrast to the conventional radon based computed tomography, wherein neutron transmission revolves around the inversion of the longitudinal ray transform that has uniqueness issues, the reconstruction in the proposed algorithm is based on the least squares approach, constrained by an equilibrium formulated through the finite element method. References B. Abbey, S. Y. Zhang, W. J. J. Vorster, and A. M. Korsunsky. Feasibility study of neutron strain tomography. Proc. Eng., 1\penalty 0 (1):185–188, 2009. doi:10.1016/j.proeng.2009.06.043. R. Aggarwal, M. H. Meylan, B. P. Lamichhane, and C. M. Wensrich. Energy resolved neutron imaging for strain reconstruction using the finite element method. J. Imag., 6(3):13, 2020. doi:10.3390/jimaging6030013. J. N. Hendriks, A. W. T. Gregg, C. M. Wensrich, A. S. Tremsin, T. Shinohara, M. Meylan, E. H. Kisi, V. Luzin, and O. Kirsten. Bragg-edge elastic strain tomography for in situ systems from energy-resolved neutron transmission imaging. Phys. Rev. Mat., 1:053802, 2017. doi:10.1103/PhysRevMaterials.1.053802. C. Jidling, J. Hendriks, N. Wahlstrom, A. Gregg, T. B. Schon, C. Wensrich, and A. Wills. Probabilistic modelling and reconstruction of strain. Nuc. Inst. Meth. Phys. Res. B, pages 141–155, 2018. doi:10.1016/j.nimb.2018.08.051. W. R. B. Lionheart and P. J. Withers. Diffraction tomography of strain. Inv. Prob., 31:045005, 2015. doi:10.1088/0266-5611/31/4/045005. C. E. Rasmussen and C. K. I. Williams. Gaussian processes for machine learning. MIT Press, 2006. URL https://mitpress.mit.edu/books/gaussian-processes-machine-learning. C. M. Wensrich, E. Kisi, V. Luzin, and O. Kirstein. Non-contact measurement of the stress within granular materials via neutron diffraction. AIP Conf. Proc., 1542:441–444, 2013. doi:10.1063/1.4811962. R. Woracek, J. Santisteban, A. Fedrigo, and M. Strobl. Diffraction in neutron imaging–-a review. Nuc. Inst. Meth. Phys. Res. A, 878:141–158, 2018. doi:10.1016/j.nima.2017.07.040.

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