Crystallography of Natural and Synthetic Gold Alloy Microstructures

2013 ◽  
Vol 753 ◽  
pp. 477-480 ◽  
Author(s):  
Angela Halfpenny ◽  
Robert Hough ◽  
Michael Nugus
Keyword(s):  
Lattice Distortion ◽  
Electron Backscatter Diffraction ◽  
Gold Foil ◽  
Gold Deposition ◽  
Synthetic Sample ◽  
Coarse Grains ◽  
Formation Conditions ◽  
Backscatter Diffraction ◽  
Gold Microstructures ◽  
Natural And Synthetic

To improve our understanding of the mechanisms of gold deposition, a comparison was made of the microstructures of a natural gold sample with a synthetic gold foil of similar alloy composition (approximately Au 90%, Ag 10%). The aim was to identify any similarities between the samples that could help increase our knowledge of how the natural gold microstructures formed and were modified post-mineralisation. The samples were analysed using electron backscatter diffraction to map their microstructure, with the synthetic gold foil then heated to and mapped at 400°C, 500°C, 600°C and 700°C. Both the natural and synthetic sample exhibited a dominance of ∑3 twin boundaries, but these were much less abundant in the synthetic sample prior to heating. The natural sample is dominated by coarse grains exhibiting lattice distortion and low angle grain boundaries, which more closely resemble the synthetic gold foil microstructure after recrystallisation has taken place, than the initial microstructure, implying that the grains have had time to grow. Performing experiments such as these allows direct comparison of gold microstructures where the formation conditions are known and the controlling mechanisms can be determined. This will improve our understanding of the important mechanisms behind gold deposition.

Numerical and Experimental Investigation on the Hybrid Superplastic Forming of the Conical Mg Alloy Component

2018 ◽  
Vol 385 ◽  
pp. 391-396
Author(s):  
Mei Ling Guo ◽  
Ming Jen Tan ◽  
Xu Song ◽  
Beng Wah Chua
Keyword(s):  
Electron Backscatter Diffraction ◽  
Thickness Distribution ◽  
Superplastic Forming ◽  
Test Results ◽  
Forming Process ◽  
Hyperbolic Sine ◽  
Coarse Grains ◽  
Hot Drawing ◽  
Material Forming ◽  
Backscatter Diffraction

Hybrid superplastic forming (SPF) is a novel sheet metal forming technique that combines hot drawing with gas forming process. Compared with the conventional SPF process, the thickness distribution of AZ31B part formed by this hybrid SPF method has been significantly improved. Additionally, the microstructure evolution of AZ31 was examined by electron backscatter diffraction (EBSD). Many subgrains with low misorientation angle were observed in the coarse grains during SPF. Based on the tensile test results, parameters of hyperbolic sine creep law model was determined at 400 oC. The hybrid SPF behavior of non-superplastic grade AZ31B was predicted by ABAQUS using this material forming model. The FEM results of thickness distribution, thinning characteristics and forming height were compared with the experimental results and have shown reasonable agreement with each other.

An Study of Nanoscale Mechanical Twins in GH4169 Alloy by Laser Shot Peening Processing

2021 ◽  
Vol 1027 ◽  
pp. 155-162
Author(s):  
Qiang Wang
Keyword(s):  
Shot Peening ◽  
Electron Backscatter Diffraction ◽  
Laser Shot ◽  
Near Surface ◽  
Refined Grains ◽  
Transmission Electron ◽  
Coarse Grains ◽  
Mechanical Twins ◽  
Backscatter Diffraction ◽  
Gh4169 Alloy

In order to study the mechanism of the fatigue strengthening using laser shot peening in GH4169 alloy, micro-structural and nanoscale mechanical twins (MT) at different depth below the top surface subjected to laser shot peening processing (LSP) were investigated by means of electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) observations. In terms of the experimental observations and analyses, the formation of refined grains and nanoscale MT mechanism at the near surface of GH4169 alloy as a function of LSP treament can be summarized as follows: (i) two direction low density of MTs divide the initial coarse grains into submicron rhombic blocks; (ii) high density of MTs aligned in two directions subdivide the submicron rhombic blocks into nanoscale rhombic MT blocks; (iii) the third direction MT further refine the nanoscale rhombic MT blocks into nanoscale triangular MT blocks; (iv) some of subdivided blocks evolve into refined grains. An ultra-high strain rate induced by ultra-short laser pulse plays a key role in the formation of refined grains and nanoscale MT during plastic deformation of GH4169 alloy subjected to LSP treatment.

Crystallographic correlation between 5M and 7M martensite in an Ni–Mn–Ga alloy

2016 ◽  
Vol 49 (2) ◽  
pp. 507-512
Author(s):  
Zongbin Li ◽  
Zhenzhuang Li ◽  
Bo Yang ◽  
Yudong Zhang ◽  
Claude Esling ◽  
...  
Keyword(s):  
Lattice Distortion ◽  
Electron Backscatter Diffraction ◽  
Deep Insight ◽  
Ferromagnetic Shape Memory Alloys ◽  
Electron Backscatter ◽  
Ferromagnetic Shape Memory ◽  
Backscatter Diffraction ◽  
Orientation Determination ◽  
Specific Orientation ◽  
Insight Into

In Ni–Mn–Ga ferromagnetic shape memory alloys, a structural transformation from one type of martensite to another is frequently observed upon cooling or heating. In this work, the microstructural features associated with the transformation from 5M to 7M martensite in an Ni50Mn26Ga22Cu2 alloy were studied. On the basis of the crystallographic orientation determination and an examination of the microstructure by means of the electron backscatter diffraction technique, the 5M to 7M transformation was found to be accompanied by the thickening of martensite plates. The two kinds of martensite (5M and 7M) possess a specific orientation relationship with (001)5M//(001)7M and [100]5M//[100]7M. Through further lattice distortion, four types of 5M variant can evolve into four 7M martensite variants in one variant colony. The present study is expected to provide a deep insight into the crystallographic correlation between 5M and 7M martensite in Ni–Mn–Ga alloys.

The Occurrence of a Peripheral Coarse Grain Zone (PCGZ) in Extruded Bars of AA 7108

2021 ◽  
Vol 1016 ◽  
pp. 1141-1146
Author(s):  
Saul Hissaci de Souza ◽  
Ronald Lesley Plaut ◽  
Nelson Batista de Lima ◽  
Rene Ramos de Oliveira ◽  
Angelo Fernando Padilha
Keyword(s):  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Polarized Light ◽  
Coarse Grain ◽  
X Ray Diffraction ◽  
Rectangular Section ◽  
X Ray ◽  
Analysis Techniques ◽  
Coarse Grains ◽  
Backscatter Diffraction

Industrial-scale extruded profiles of AA 7108 with a rectangular section (25.60 mm x 15.95 mm) were used in this investigation. Some complementary microstructural analysis techniques, such as polarized light microscopy, EBSD (Electron Backscatter Diffraction) and X-ray diffraction were used to characterize the microstructure, focusing on the PCG zone. It was observed that the extruded profiles presented a totally recrystallized microstructure and a 300 μm layer of peripheral coarse grains. Additionally, the results showed that the PCGZ predominant grain orientation {311} <110> differs from the texture below the PCGZ (Goss and Cube components).

scholarly journals The microstructure of meteoric ice from Vostok, Antarctica

2007 ◽  
Vol 53 (180) ◽  
pp. 41-62 ◽  
Author(s):  
Rachel Obbard ◽  
Ian Baker
Keyword(s):  
Electron Backscatter Diffraction ◽  
Impurity Content ◽  
Microstructural Development ◽  
Glacial Ice ◽  
Fine Grained ◽  
Grain Boundary Mobility ◽  
Coarse Grains ◽  
Vostok Station ◽  
Glacial Periods ◽  
Backscatter Diffraction

AbstractThe 3623 m long, 5G core collected at Vostok station, Antarctica, contains alternating layers of meteoric ice with two distinctly different microstructures. In this paper, we present the microstructure and impurity content of a number of specimens ranging in depth from 97 to 3416 m, describe in detail the characteristics of the different layers and propose a mechanism for their microstructural development. Digital image analysis, ion chromatography, scanning electron microscopy and energy dispersive X-ray spectroscopy were used to measure texture and the location and type of impurities; electron backscatter diffraction was used to determine crystal orientation. The ice associated with interglacial periods is characterized by relatively coarse grains and a strong preferred orientation of the c axes in a plane encompassing the coring direction, producing a vertical-girdle fabric. In contrast, ice from glacial periods is characterized by a much smaller grain size and a strong singlemaximum fabric, where the c axes are clustered around the vertical. Calcium is uniquely present in the grain boundaries of the fine-grained glacial layers, and its effect on grain-boundary mobility and the misorientation dependence of mobility can explain the development of the discontinuous microstructure seen in glacial ice at Vostok station.

Effect of Local Texture on the Orange Peel Defect in St14 Steel Sheet

2005 ◽  
Vol 495-497 ◽  
pp. 167-172
Author(s):  
Sheng Quan Cao ◽  
Jin Xu Zhang ◽  
Jian Sheng Wu ◽  
Jia Guang Chen
Keyword(s):  
Slip System ◽  
Steel Sheet ◽  
Electron Backscatter Diffraction ◽  
Orange Peel ◽  
Phase Zone ◽  
Coarse Grains ◽  
Schmid Factor ◽  
Ebsd Technique ◽  
Backscatter Diffraction ◽  
St14 Steel

In this paper, the ‘orange peel’ defect in the surface range of the st14 steel sheet has been investigated using the electron backscatter diffraction (EBSD) technique. It has been found that the ‘orange peel’ defect in the st14 steel sheet was resulted from the local coarse grains which were produced during hot-rolling due to the critical deformation in dual-phase zone; During deep drawing, the coarse grains with {100}<001> microtexture can slip on the {112}<111> slip system to form bulging and yields orange peel defects, while the coarse grains with {112}<110> orientation do not form the defect as the Schmid factor of {112}<111> slip system in it equals zero.

Performance of Dynamically Simulated Reference Patterns for Cross-Correlation Electron Backscatter Diffraction

2016 ◽  
Vol 22 (4) ◽  
pp. 789-802 ◽  
Author(s):  
Brian E. Jackson ◽  
Jordan J. Christensen ◽  
Saransh Singh ◽  
Marc De Graef ◽  
David T. Fullwood ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Lattice Distortion ◽  
Electron Backscatter Diffraction ◽  
Noise Levels ◽  
Reference Pattern ◽  
Electron Backscatter ◽  
Correlation Techniques ◽  
Low Levels ◽  
Backscatter Diffraction ◽  
Dynamical Patterns

AbstractHigh-resolution (or “cross-correlation”) electron backscatter diffraction analysis (HR-EBSD) utilizes cross-correlation techniques to determine relative orientation and distortion of an experimental electron backscatter diffraction pattern with respect to a reference pattern. The integrity of absolute strain and tetragonality measurements of a standard Si/SiGe material have previously been analyzed using reference patterns produced by kinematical simulation. Although the results were promising, the noise levels were significantly higher for kinematically produced patterns, compared with real patterns taken from the Si region of the sample. This paper applies HR-EBSD techniques to analyze lattice distortion in an Si/SiGe sample, using recently developed dynamically simulated patterns. The results are compared with those from experimental and kinematically simulated patterns. Dynamical patterns provide significantly more precision than kinematical patterns. Dynamical patterns also provide better estimates of tetragonality at low levels of distortion relative to the reference pattern; kinematical patterns can perform better at large values of relative tetragonality due to the ability to rapidly generate patterns relating to a distorted lattice. A library of dynamically generated patterns with different lattice parameters might be used to achieve a similar advantage. The convergence of the cross-correlation approach is also assessed for the different reference pattern types.

Characters of Coarse Grains Subdivisions in Rolled Polycrystalline Al

2007 ◽  
Vol 546-549 ◽  
pp. 1033-1036
Author(s):  
Qi Ping Hu ◽  
Yong Zhang ◽  
Yun Lai Deng
Keyword(s):  
High Purity ◽  
Electron Backscatter Diffraction ◽  
Coarse Grains ◽  
Electron Backscatter ◽  
Columnar Grains ◽  
Cold Rolled ◽  
Ebsd Technique ◽  
The Individual ◽  
Individual Grains ◽  
Backscatter Diffraction

Deformation microstructures and micro-orientations of columnar grains with different orientations in a polycrystalline high purity Al cold-rolled up to 65% (thickness reduction) were investigated using electron backscatter diffraction (EBSD) technique. It was found that rotations were Inhomogeneous within the individual grains, the rotation angles of the parts close to the initial boundaries (BPs) were smaller than those remote from the boundaries (IPs), e.g. the deviation angles between the BPs and the IPs were 5-6° in the grains with <001>//RD orientation, leading to the rotation along the α-fiber, while the deviation angles were 5-12° in the grains with <121>//ND orientation rotating toward the β-fiber. These results demonstrated that the microstructures and local rotations of various parts within the rolled individual columnar grains were influenced by their initial orientations and boundaries.

Electron backscatter diffraction study of variant selection during ordering phase transformation in L10-type red gold alloy

2019 ◽  
Vol 52 (5) ◽  
pp. 1202-1213 ◽  
Author(s):  
Margaux N. D. Larcher ◽  
Cyril Cayron ◽  
Andreas Blatter ◽  
Raphaëlle Soulignac ◽  
Roland E. Logé
Keyword(s):  
Lattice Distortion ◽  
Gold Alloy ◽  
Electron Backscatter Diffraction ◽  
Martensitic Transformations ◽  
Careful Analysis ◽  
Mechanical Work ◽  
Variant Selection ◽  
Ebsd Data ◽  
Electron Backscatter ◽  
Backscatter Diffraction

A shape-memory effect is known to appear in red gold alloys with compositions close to Au–Cu. The aim of this paper is to study by electron backscatter diffraction (EBSD) the variant selection in the A1 → L10 transformation occurring under stress, in bending conditions. The L10 domains are successfully identified by this technique despite the c/a ratio being close to unity. The orientation relationship between the cubic and tetragonal phases is determined by a careful analysis of the EBSD data. The distortion of the lattice for each variant is then modelled and calculated from the experimental orientations. The mechanical work associated with the transformation is computed from the lattice distortion by neglecting the obliquity. Finally, the distribution of this mechanical work is compared with the case of a uniform distribution of all variants, in order to evaluate the extent of variant selection. The maximal work criterion, often used for martensitic transformations, enabled quantification of the variant selection phenomenon.

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