Controllable mechanical anisotropy of selective laser melted Ti6Al4V: A new perspective into the effect of grain orientations and primary grain structure

Laser forming of metal sheet is a forming technology of sheet without a die that the sheet is deformed by internal thermal stress induced by partially irradiation of a laser beam. In this paper, the bending behavior of common stainless steel 1Cr18Ni9 sheet is studied after being irradiated by straight line with a Nd:YAG pulsed laser beam. The aim of the investigation is to find out the relationship of the physical behaviors of heat affected zone (HAZ) with the pulse parameters of the laser. Through the analysis of the fundamental theory of pulsed laser affected, this paper shows the affected characteristics of metal sheet with pulsed laser forming. The results show that the microstructure of HAZ of pulsed laser scanned is layered, and the micro-hardness is improved than that in matrix. The microstructures show that the deformed grain structure is inhomogeneous, that caused the grain sizes and grain orientations in HAZ to become different. By qualitative analysis of experimental result, the conclusion obtained may provide basis for theoretical investigation and possible industrial application of laser forming process in the future.

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The Influence of Crystallographic Orientations of Grains on Microstructurally Small Cracks Using Crystal Plasticity and Random Grain Structure

Volume 6: Materials and Fabrication ◽

10.1115/pvp2006-icpvt-11-93363 ◽

2006 ◽

Cited By ~ 1

Author(s):

I. Simonovski ◽

L. Cizelj

Keyword(s):

Crystal Plasticity ◽

Crack Tip ◽

Maximum Load ◽

Grain Structure ◽

Crystal Plasticity Model ◽

Grain Orientations ◽

Small Cracks ◽

Crack Tip Opening ◽

Soft Grains ◽

Crystallographic Orientations

A plane-strain finite element crystal plasticity model of microstructurally small stationary crack emanating at a surface grain in a 316L stainless steel is proposed. The model consisting of 212 randomly shaped, sized and oriented grains is loaded monotonically in uniaxial tension to a maximum load of 1.12Rp0.2 (280 MPa). The influence that a random grain structure imposes on a Stage I crack is assessed by calculating the crack tip opening (CTOD) and sliding displacements (CTSD), considering also different crystallographic orientations. It is shown that certain crystallographic orientations result in a cluster of soft grains around the crack-containing grain. In these cases the crack tip can become apart of the localized strain, resulting in a large CTOD value. This effect, resulting from the overall grain orientations and sizes, can have a greater impact on the CTOD than the local grain orientation. On the other hand, when a localized soft response is formed away from the crack, the localized strain does not affect the crack tip directly, resulting in a small CTOD value. The resulting difference in CTOD can be up to a factor of 4, depending upon the crystallographic set. Grains as far as 6xCracklength significantly influence that crack tip parameters. It was also found the a larger crack-containing grain tends to increase the CTOD.

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Optical characterization of silicon carbide polytypes

Canadian Journal of Physics ◽

10.1139/p96-864 ◽

1996 ◽

Vol 74 (S1) ◽

pp. 225-232

Author(s):

J. W. Bowron ◽

S. Damaskinos ◽

A. E. Dixon

Keyword(s):

Collection Efficiency ◽

Outer Edge ◽

Crystal Defects ◽

Grain Structure ◽

Impurity Level ◽

Deep Impurity ◽

Spatially Resolved ◽

Reflected Light ◽

Grain Orientations ◽

Spectrally Resolved

A modified experimental scanning laser photoluminescence microscope was used to perform spatially and spectrally resolved measurements on a SiC sample. A scanning grating monochromator integrated into the detection arm of the microscope yielded a high photon collection efficiency at the detector. A cold-finger stage mounted directly onto the X-Y translation stages of the microscope allowed low-temperature PL measurements to be made. One object of the experiment was to test the hypothesis that spectrally and spatially resolved PL could be used to identify different polytypes associated with the grain structure observed in reflected light. Four different regions of the SiC sample were identified and three of these were correlated with low spatial resolution X-ray measurements and found to be polytypes 4H, 6H, and 33R–(α)SiC. Room-temperature photoluminescence was used to map the distribution of a deep impurity level and to map crystal defects. Reflected-light measurements were used to map different grain orientations of SiC. The sample was observed to be polycrystalline with most of the grains at the outer edge of the sample.

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Deep Learning Based Inversion of Locally Anisotropic Weld Properties from Ultrasonic Array Data

Applied Sciences ◽

10.3390/app12020532 ◽

2022 ◽

Vol 12 (2) ◽

pp. 532

Author(s):

Jonathan Singh ◽

Katherine Tant ◽

Anthony Mulholland ◽

Charles MacLeod

Keyword(s):

Real Time ◽

Signal To Noise Ratio ◽

Computational Cost ◽

Scattered Wave ◽

Training Data ◽

Grain Structure ◽

Time Data ◽

Grain Orientations ◽

Weld Properties ◽

Crystallographic Orientations

The ability to reliably detect and characterise defects embedded in austenitic steel welds depends on prior knowledge of microstructural descriptors, such as the orientations of the weld’s locally anisotropic grain structure. These orientations are usually unknown but it has been shown recently that they can be estimated from ultrasonic scattered wave data. However, conventional algorithms used for solving this inverse problem incur a significant computational cost. In this paper, we propose a framework which uses deep neural networks (DNNs) to reconstruct crystallographic orientations in a welded material from ultrasonic travel time data, in real-time. Acquiring the large amount of training data required for DNNs experimentally is practically infeasible for this problem, therefore a model based training approach is investigated instead, where a simple and efficient analytical method for modelling ultrasonic wave travel times through given weld geometries is implemented. The proposed method is validated by testing the trained networks on data arising from sophisticated finite element simulations of wave propagation through weld microstructures. The trained deep neural network predicts grain orientations to within 3° and in near real-time (0.04 s), presenting a significant step towards realising real-time, accurate characterisation of weld microstructures from ultrasonic non-destructive measurements. The subsequent improvement in defect imaging is then demonstrated via use of the DNN predicted crystallographic orientations to correct the delay laws on which the total focusing method imaging algorithm is based. An improvement of up to 5.3 dB in the signal-to-noise ratio is achieved.

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Prediction of the Plastic Anisotropy of Rolled Sheets under a Combined Effect of Texture, Grain Shape and Grain Size

Materials Science Forum ◽

10.4028/www.scientific.net/msf.702-703.182 ◽

2011 ◽

Vol 702-703 ◽

pp. 182-187 ◽

Cited By ~ 2

Author(s):

Laurent Delannay

Keyword(s):

Grain Size ◽

Grain Shape ◽

Plastic Anisotropy ◽

Separation Distance ◽

Combined Effect ◽

Grain Structure ◽

Mechanical Anisotropy ◽

General Situation ◽

Slip Systems ◽

Individual Grains

The present study explores a way to improve predictions of the mechanical anisotropy of textured polycrystalline aggregates. The underlying hypothesis is that grain-shape-dependent backstresses developed during the elastic-plastic transition influence the selection of active slip systems inside individual grains. Recently, a model was developed and applied successfully to electro-deposited pure iron with a columnar grain structure \cite{Delannay2011}. In the present study, we first suggest another definition of the boundary separation distance experienced by individual slip systems. Then, the model is adapted from the case of spheroidal grains, considered initially, to the more general situation of ellipsoidal grains. A combined effect of grain size, grain shape and texture on plastic anisotropy at yielding is illustrated in case of a rolled IF steel sheet.

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Grain orientations and grain boundary networks of YBa2Cu3O7−δ films deposited by metalorganic and pulsed laser deposition on biaxially textured Ni–W substrates

Journal of Materials Research ◽

10.1557/jmr.2006.0110 ◽

2006 ◽

Vol 21 (4) ◽

pp. 923-934 ◽

Cited By ~ 43

Author(s):

D.M. Feldmann ◽

T.G. Holesinger ◽

C. Cantoni ◽

R. Feenstra ◽

N.A. Nelson ◽

...

Keyword(s):

Grain Boundary ◽

Pulsed Laser Deposition ◽

Pulsed Laser ◽

Laser Deposition ◽

Grain Structure ◽

Ex Situ ◽

Full Width ◽

Out Of Plane ◽

Grain Orientations ◽

Processed Sample

We report a detailed study of the grain orientations and grain boundary (GB) networks in YBa2Cu3O7-δ (YBCO) films ∼0.8 μm thick grown by both the in situ pulsed laser deposition (PLD) process and the ex situ metalorganic deposition (MOD) process on rolling-assisted biaxially textured substrates (RABiTS). The PLD and MOD growth processes result in columnar and laminar YBCO grain structures, respectively. In the MOD-processed sample [full-width critical current density Jc(0 T, 77 K) = 3.4 MA/cm2], electron back-scatter diffraction (EBSD) revealed an improvement in both the in-plane and out-of-plane alignment of the YBCO relative to the template that resulted in a significant reduction of the total grain boundary misorientation angles. A YBCO grain structure observed above individual template grains was strongly correlated to larger out-of-plane tilts of the template grains. YBCO GBs meandered extensively about their corresponding template GBs and through the thickness of the film. In contrast, the PLD-processed film [full width Jc(0 T, 77 K) = 0.9 MA/cm2] exhibited nearly perfect epitaxy, replicating the template grain orientations. No GB meandering was observed in the PLD-processed film with EBSD. Direct transport measurement of the intra-grain Jc(0 T, 77 K) values of PLD and MOD-processed films on RABiTS revealed values up to 4.5 and 5.1 MA/cm2, respectively. As the intra-grain Jc values were similar, the significantly higher full-width Jc for the MOD-processed sample is believed to be due to the improved grain alignment and extensive GB meandering.

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Modification of the Mechanical Anisotropy in Extruded AZ31 Sheets

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.473.490 ◽

2011 ◽

Vol 473 ◽

pp. 490-497 ◽

Cited By ~ 1

Author(s):

N. Grittner ◽

M. Engelhardt ◽

M. Hepke ◽

Dirk Bormann ◽

Bernd Arno Behrens ◽

...

Keyword(s):

Mechanical Properties ◽

Sheet Material ◽

Microstructural Analysis ◽

Rolling Direction ◽

Tensile Tests ◽

Grain Structure ◽

Mechanical Anisotropy ◽

Roll Forming ◽

Extrusion Press ◽

Grain Distribution

Due to its low density and good mechanical properties Magnesium holds a high potential for design applications. The investigations discussed herein focus on the use of extruded magnesium sheets as semi-finished products e.g. for subsequent processing by roll forming. Special interest is given by the hcp-structure of magnesium which reduces forming abilities. Extrusion experiments using AZ31 were carried out to investigate the influence of different die geometries (S = sharp-edged and R= radius), billet temperatures (TB= 350°C and 390°C) and extrusion speeds (vext= 2.31 m/min and 9.24 m/min) on mechanical properties, grain structure and texture of said alloy. Two types of sheets with the dimensions of 80 x 1 mm and 80 x 2 mm respectively were produced using the institutes 10 MN extrusion press make SMS MEER. Sheet material with a thickness of 1 mm rolled from cast billets has been used for reference. Microstructural analysis focused on recrystallization behavior and grain size as well as grain distribution within the sheets. Tensile tests in extrusion or rolling direction as well as 45° and 90° to the same showed a strong influence of the specimen orientation on the mechanical properties. Additional Erichsen cupping tests demonstrated the stretch-forming capacity of the different test set-ups.

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Mechanism of Etching of Al-4.5Mg-1.0Mn Alloy

Microscopy and Microanalysis ◽

10.1017/s1431927618012400 ◽

2018 ◽

Vol 24 (4) ◽

pp. 374-386 ◽

Cited By ~ 1

Author(s):

Aline D. Gabbardo ◽

Xi Wang ◽

Angeire Huggins ◽

G. S. Frankel

Keyword(s):

Phosphoric Acid ◽

Intergranular Corrosion ◽

Energy Dispersive Spectrometry ◽

Surface Profile ◽

Grain Structure ◽

Force Microscopy ◽

Atomic Force ◽

Corrosion Evaluation ◽

Grain Orientations ◽

Contrast Image

Abstract5xxx series aluminum alloys, as Al-4.5Mg-1.0Mn (AA5083), are strengthened by Mg solid solution and work hardening. A drawback of this alloy is the fact that β phase, Al3Mg2, can precipitate on grain boundaries causing sensitization and intergranular corrosion, which is detrimental to the integrity of the structure. Metallography is an important technique to study the grain structure and highly sought for intergranular corrosion evaluation; however, revealing the grains of completely un-sensitized AA5083 is challenging. This paper introduces a new procedure to etch AA5083 samples that were solutionized at 450°C for 1.5 h. The new procedure is a two-step etching method, including a phosphoric acid pre-etching step and a Weck’s reagent coloring step. Solutionized, lightly sensitized, and as-received AA5083 were evaluated, and the grains were observed using optical microscopy. The microetching mechanism was further studied by optical profilometry, atomic force microscopy, scanning electron microscopy, and energy dispersive spectrometry. The phosphoric acid created a surface profile determined by the grain orientations and its reactivity, and the Weck’s reagent was then able to color grains by preferential MnO2 formation over some pre-etched grains. Moreover, the final polishing with colloidal silica was essential to reach a high contrast image.

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Spatial Uniformity of the Rate of Grain Coarsening in a Submicron Al-Sc Alloy Produced by Severe Plastic Deformation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.503-504.251 ◽

2006 ◽

Vol 503-504 ◽

pp. 251-258

Author(s):

Michael Ferry

Keyword(s):

Fine Particles ◽

Grain Structure ◽

Processing Route ◽

Grain Coarsening ◽

Boundary Character ◽

Angular Pressing ◽

Grain Boundary Character ◽

Uniform Dispersion ◽

Grain Orientations ◽

The Difference

The uniformity of grain coarsening throughout the microstructure of a submicron grained particle-containing aluminium alloy has been investigated using high resolution EBSD. The alloy was processed by equal channel angular pressing (ECAP) and low temperature ageing to generate ~0.8 􀁐m diameter grain structure containing a relatively uniform dispersion of nanosized Al3Sc particles. While the initial processing route generated a uniform grain size distribution, the distribution of grain orientations was rather inhomogeneous with certain regions of microstructure containing colonies of grains consisting predominantly of either HAGBs or LAGBs. It was found that, despite the difference in grain boundary character between these regions, the fine particles produced by pre-ageing promote uniform coarsening throughout the microstructure despite the marked differences in boundary character between these regions. An analytical model is outlined which predicts the uniformity of grain coarsening in particle-containing alloys despite the presence of orientation gradients in the microstructure.

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Thermoelectric response from grain boundaries and lattice distortions in crystalline gold devices

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2002284117 ◽

2020 ◽

Vol 117 (38) ◽

pp. 23350-23355

Author(s):

Charlotte I. Evans ◽

Rui Yang ◽

Lucia T. Gan ◽

Mahdiyeh Abbasi ◽

Xifan Wang ◽

...

Keyword(s):

Grain Boundaries ◽

Electron Backscatter Diffraction ◽

Mean Free Path ◽

Grain Structure ◽

Metal Nanowires ◽

Structural Distortions ◽

Grain Orientations ◽

Temperature Scanning ◽

Energy Dependent ◽

Backscatter Diffraction

The electronic Seebeck response in a conductor involves the energy-dependent mean free path of the charge carriers and is affected by crystal structure, scattering from boundaries and defects, and strain. Previous photothermoelectric (PTE) studies have suggested that the thermoelectric properties of polycrystalline metal nanowires are related to grain structure, although direct evidence linking crystal microstructure to the PTE response is difficult to elucidate. Here, we show that room temperature scanning PTE measurements are sensitive probes that can detect subtle changes in the local Seebeck coefficient of gold tied to the underlying defects and strain that mediate crystal deformation. This connection is revealed through a combination of scanning PTE and electron microscopy measurements of single-crystal and bicrystal gold microscale devices. Unexpectedly, the photovoltage maps strongly correlate with gradually varying crystallographic misorientations detected by electron backscatter diffraction. The effects of individual grain boundaries and differing grain orientations on the PTE signal are minimal. This scanning PTE technique shows promise for identifying minor structural distortions in nanoscale materials and devices.

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