scholarly journals The Role of Lengthscale in the Creep of Sn-3Ag-0.5Cu Solder Microstructures

2021 ◽  
Vol 50 (3) ◽  
pp. 926-938
Author(s):  
Tianhong Gu ◽  
Christopher M. Gourlay ◽  
T. Ben Britton
Keyword(s):  
Electron Backscatter Diffraction ◽  
Constant Load ◽  
Structural Deformation ◽  
Dislocation Creep ◽  
Diffusion Creep ◽  
Directionally Solidified ◽  
Strain Rate Change ◽  
Loading Direction ◽  
Backscatter Diffraction

AbstractCreep of directionally solidified Sn-3Ag-0.5Cu wt.% (SAC305) samples with near-<110> orientation along the loading direction and different microstructural lengthscale is investigated under constant load tensile testing and at a range of temperatures. The creep performance improves by refining the microstructure, i.e. the decrease in secondary dendrite arm spacing (λ2), eutectic intermetallic spacing (λe) and intermetallic compound (IMC) size, indicating a longer creep lifetime, lower creep strain rate, change in activation energy (Q) and increase in ductility and homogeneity in macro- and micro-structural deformation of the samples. The dominating creep mechanism is obstacle-controlled dislocation creep at room temperature and transits to lattice-associated vacancy diffusion creep at elevated temperature ($$ \frac{T}{{T_{M} }} $$ T T M  > 0.7 to 0.75). The deformation mechanisms are investigated using electron backscatter diffraction and strain heterogeneity is identified between β-Sn in dendrites and β-Sn in eutectic regions containing Ag3Sn and Cu6Sn5 particles. The size of the recrystallised grains is modulated by the dendritic and eutectic spacings; however, the recrystalised grains in the eutectic regions for coarse-scaled samples (largest λ2 and λe) is only localised next to IMCs without growth in size.

A Role of Low Energy Grain Boundaries in the Abnormal Grain Growth in Fe-3%Si Alloy

2011 ◽  
Vol 127 ◽  
pp. 89-94 ◽  
Author(s):  
Ye Chao Zhu ◽  
Jiong Hui Mao ◽  
Fa Tang Tan ◽  
Xue Liang Qiao
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Electron Backscatter Diffraction ◽  
Dominant Role ◽  
Coincidence Site Lattice ◽  
Diffraction Method ◽  
Abnormal Grain Growth ◽  
Low Energy ◽  
Backscatter Diffraction

Low energy grain boundaries were considered to be important in abnormal grain growth by theoretical deduction. The disorientation angles and coincidence site lattice grain boundaries distribution of more than 20 Goss grains and their neighboring matrix grains in primary recrystallized Fe-3%Si alloy were investigated using an electron backscatter diffraction method. It was found that the frequency of low energy grain boundaries of Goss grains which are more likely to abnormally grow are higher than their neighboring matrix grains, which indicated that low energy grain boundaries play a dominant role in the abnormal grain growth of Fe-3%Si alloy. The result meets well with the abnormal grain growth theory.

scholarly journals Grain Refinement by Extension Twin in Mg Alloy during Asymmetrical Rolling

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 891 ◽  
Author(s):  
I Widiantara ◽  
Hae Yang ◽  
Muhammad Kamil ◽  
Dong Yoon ◽  
Young Ko
Keyword(s):  
Grain Refinement ◽  
Electron Backscatter Diffraction ◽  
Surface Region ◽  
Mg Alloy ◽  
Speed Ratio ◽  
Asymmetrical Rolling ◽  
Present Sample ◽  
Refinement Process ◽  
Backscatter Diffraction

The work looked into the grain refinement process of Mg alloy during asymmetrical rolling with a focus on the role of twin. The present sample was deformed at ambient temperature by single operation with the height reduction of 50% at the roll speed ratio of 1:4 for the upper and lower rolls having the same dimension. From the electron backscatter diffraction analysis in the surface region where intense shear strain was imparted, a number of { 10 1 ¯ 2 } extension twins with a width of ~1 µm were detected clearly in most of the deformed grains. Moreover, the average misorientation angle of the deformed grains in the top region was found to be ~32°, which was two times higher than that in the center area where the extension twin was detected rarely. As a result, the microstructure in the top region was refined significantly down to be ~1.1 µm with an aid of twin activities that would be discussed in this study.

Hydrogen effects on fracture of high-strength steels with different micro-alloying

2015 ◽  
Vol 33 (6) ◽  
pp. 515-527 ◽  
Author(s):  
Olga Todoshchenko ◽  
Yuriy Yagodzinskyy ◽  
Valentina Yagodzinska ◽  
Tapio Saukkonen ◽  
Hannu Hänninen
Keyword(s):  
Chemical Composition ◽  
Electron Backscatter Diffraction ◽  
High Strength Steels ◽  
Thermal Desorption Spectroscopy ◽  
High Strength ◽  
Constant Load ◽  
Carbon Steels ◽  
Hydrogen Induced Cracking ◽  
Load Tests ◽  
Backscatter Diffraction

AbstractConstant load tests of high-strength carbon steels with different micro-alloying using strengths in the range of 1000–1400 MPa were performed at ambient temperature under continuous electrochemical hydrogen charging. Hydrogen markedly affects delayed fracture of all the studied steels. Fractography of the studied steels shows that fracture mechanism depends on the chemical composition of the studied steels and hydrogen-induced cracking exhibits intergranular or transgranular character occurring often in the form of hydrogen flakes. The size and chemical composition of non-metallic inclusions are analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Hydrogen-induced cracking initiates at TiN/TiC particles in steels with Ti alloying. Crack paths are studied with electron backscatter diffraction mapping to analyze crack initiation and growth. The thermal desorption spectroscopy method is used to analyze the distribution of hydrogen in the trapping sites. The mechanisms of hydrogen effects on fracture of high-strength steels are discussed.

scholarly journals Dislocation Creep of Olivine and Amphibole in Amphibole Peridotites from Åheim, Norway

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1018
Author(s):  
Sejin Jung ◽  
Takafumi Yamamoto ◽  
Jun-ichi Ando ◽  
Haemyeong Jung
Keyword(s):  
Electron Microscopy ◽  
Slip System ◽  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Dislocation Creep ◽  
Transmission Electron ◽  
Electron Backscatter ◽  
Different Types ◽  
Localized Shear Deformation ◽  
Backscatter Diffraction

Amphibole peridotite samples from Åheim, Norway, were analyzed to understand the deformation mechanism and microstructural evolution of olivine and amphibole through the Scandian Orogeny and subsequent exhumation process. Three Åheim amphibole peridotite samples were selected for detailed microstructural analysis. The Åheim amphibole peridotites exhibit porphyroclastic texture, abundant subgrain boundaries in olivine, and the evidence of localized shear deformation in the tremolite-rich layer. Two different types of olivine lattice preferred orientations (LPOs) were observed: B- and A-type LPOs. Electron backscatter diffraction (EBSD) mapping and transmission electron microscopy (TEM) observations revealed that most subgrain boundaries in olivine consist of dislocations with a (001)[100] slip system. The subgrain boundaries in olivine may have resulted from the deformation of olivine with moderate water content. In addition, TEM observations using a thickness-fringe method showed that the free dislocations of olivine with the (010)[100] slip system were dominant in the peridotites. Our data suggest that the subgrain boundaries and free dislocations in olivine represent a product of later-stage deformation associated with the exhumation process. EBSD mapping of the tremolite-rich layer revealed intracrystalline plasticity in amphibole, which can be interpreted as the activation of the (100)[001] slip system.

Creep Deformation Microstructures in DS Nb-Hf-Ti-Si In-Situ Composites

1999 ◽  
Vol 5 (S2) ◽  
pp. 258-259
Author(s):  
S.D. Sitzman ◽  
B.P. Bewlay
Keyword(s):  
Creep Deformation ◽  
Microprobe Analysis ◽  
Electron Backscatter Diffraction ◽  
Czochralski Method ◽  
Directionally Solidified ◽  
Creep Tests ◽  
In Situ Composites ◽  
Before And After ◽  
Backscatter Diffraction

Directionally solidified (DS) in-situ composites based on (Nb) and (Nb) silicides, such as Nb5Si3 and Nb3Si, are presently under investigation as high-temperature structural materials [1, 2]. Alloying additions of elements such as Hf, Ti and Mo to these silicides are also being explored. The present paper describes the microstructure of a DS Nb-silicide based composite before and after creep deformation.Alloys were prepared from high purity elements (>99.9%) using induction levitation melting in a segmented water-cooled copper crucible. The alloys were directionally solidified using the Czochralski method [2]. Creep tests were conducted at 1200°C to 50% deformation. Characterization was performed using scanning electron microscopy, electron microprobe analysis (EMPA), and electron backscatter diffraction pattern analysis (EBSP).

Stabilisation of Aragonite: The Role of Mg2+ and Other Impurity Ions

2019 ◽  
Author(s):  
Matthew Boon ◽  
William Rickard ◽  
Andrew Rohl ◽  
Franca Jones
Keyword(s):  
Electron Backscatter Diffraction ◽  
Crystal Formation ◽  
Sulfate Ions ◽  
Inorganic Systems ◽  
Sodium Magnesium ◽  
Stable Product ◽  
The Stability ◽  
Backscatter Diffraction ◽  
First Time

Aragonite formation and stabilisation in seawater is still an area of active investigation since the thermodynamically stable product at room temperature is calcite. In this manuscript, purely inorganic systems that were found to stabilise aragonite were analysed by various techniques. Dynamic Light Scattering was used to characterise the nucleation behaviour of the system and it was found that the presence of magnesium ions during crystal formation inhibits nucleation overall, not just calcite nucleation. In addition, it was found that sulfate is not necessary to stabilise aragonite. Microanalysis by energy dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) revealed that the aragonite that was formed had a disordered core with, sodium, magnesium and sulfate ions incorporated into the structure. To the best of the authors’ knowledge this is the first time an ACC core in aragonite has been visualised in a completely abiotic, synthetic system (in the absence of organic molecules). Inclusion of these impurities into the structure may explain the stability of aragonite in natural seawaters.

Analysing crystal distortions to deduce dislocation slip systems

2021 ◽  
Author(s):  
John Wheeler ◽  
Sandra Piazolo ◽  
David Prior ◽  
Jake Tielke ◽  
Pat Trimby
Keyword(s):  
Electron Backscatter Diffraction ◽  
Direct Method ◽  
Grain Boundary Sliding ◽  
Dislocation Creep ◽  
Dislocation Slip ◽  
Slip Systems ◽  
Crystalline Materials ◽  
Burgers Vector ◽  
Growth Defects ◽  
Backscatter Diffraction

&lt;p&gt;In many parts of the Earth rocks deform by dislocation creep. There is therefore a need to understand which slip systems operated in nature and in experimental products. Knowing the conditions of experiments may then allow natural conditions and strain rates to be characterised. Dislocation creep typically gives lattice preferred orientations (LPOs), since activity on particular slip systems leads to lattice rotations and alignment. For decades LPOs, measured first optically and since the 1990s by EBSD, have been used to infer slip systems. This is a valuable technique but the link between slip sytem activity and LPO is complicated, especially if recrystallisation and/or grain boundary sliding have been involved.&lt;/p&gt;&lt;p&gt;Here we present a more direct method to deduce &amp;#8220;geometrically necessary&amp;#8221; dislocations (GNDs) from the distortions within crystals. Distortions may be optically visible (e.g. undulose extinction in quartz) but EBSD has revealed how common distortions are, and allowed them to be quantified. The method does not give the complete picture of GNDs but allows hypotheses to be tested about possible slip systems. We illustrate this &amp;#8220;Weighted Burgers Vector&amp;#8221; method with a number of examples. In olivine the method distinguishes slip parallel to a and c, and in plastically deformed plagioclase it reveals a variety of slip systems which would be difficuilt to deduce from LPOs alone. GNDs may not necessarily reflect the full slip system activity, since many dislocations will have passed through crystals and merged with grain boundaries leaving no signature. Neverthless the method highlights what dislocations are present &amp;#8220;stranded&amp;#8221; in the microstructure. In many case these will have been produced by deformation although the method can also characterise growth defects.&lt;/p&gt;&lt;p&gt;Wheeler et al. 2009. The weighted Burgers vector: a new quantity for constraining dislocation densities and types using electron backscatter diffraction on 2D sections through crystalline materials. &lt;span&gt;DOI:&lt;/span&gt;&amp;#160;10.1111/j.1365-2818.2009.03136.x&lt;/p&gt;

scholarly journals Microstructure Characterization of ZK60 Magnesium Alloys Using TEM and HR-EBSD

2013 ◽  
Vol 19 (S5) ◽  
pp. 8-12 ◽  
Author(s):  
Jae-Hyung Cho ◽  
Soo-Hyun Kim ◽  
Sang-Ho Han ◽  
Suk-Bong Kang
Keyword(s):  
Electron Backscatter Diffraction ◽  
Texture Evolution ◽  
Uniaxial Compression Test ◽  
Random Orientation ◽  
Loading Direction ◽  
Peak Aging ◽  
Slip Deformation ◽  
Backscatter Diffraction ◽  
Zr Alloys

AbstractZK60 (Mg–Zn–Zr) alloys exhibited a variation in precipitates with aging, and their mechanical properties also changed. Microindentation tests were carried out on two types of ZK60 alloys of solid solution (T4) and peak aging (T6). Microstructure and texture evolution during indentation was investigated using electron backscatter diffraction. Twinning occurred near the indentation marks in most grains. It was found that tensile twinning was dominant, and two twin variants were usually observed. Texture and microstructure evolution by twinning and slip activation was further examined by uniaxial compression test with strain. The initial random orientation gradually changed into basal fibers with strain. Some grains with nonbasal orientations aligned with the loading direction easily underwent twinning followed by slip deformation. Other grains near basal orientations revealed only slip deformation.

Identification and Evaluation of Freckles in Directionally Solidified Casting Made of PWA 1426 Nickel-Based Superalloy

2012 ◽  
Vol 57 (2) ◽  
pp. 559-564 ◽  
Author(s):  
B. Chmiela ◽  
M. Sozańska ◽  
J. Cwajna
Keyword(s):  
Mechanical Properties ◽  
Electron Backscatter Diffraction ◽  
Turbine Blades ◽  
Casting Defects ◽  
Directionally Solidified ◽  
Nickel Based Superalloy ◽  
Aero Engine ◽  
And Performance ◽  
Backscatter Diffraction ◽  
Equiaxed Grains

Identification and Evaluation of Freckles in Directionally Solidified Casting Made of PWA 1426 Nickel-Based SuperalloyManufacturing of modern aero engine turbine blades made of nickel-based superalloys is very complex and expensive. The thrust and performance of new engines must address constantly more demanding requirements. Therefore, turbine blades must be characterised by very good mechanical properties, which is possible only if the blades are free of casting defects. An important innovation has been the launching of directionally solidified (DS) and single crystal (SX) turbine blades. But, manufacturing procedures and the chemical composition of many superalloys promote the formation of casting defects that are characteristic only for directional solidification. One of these defects is freckles. Freckles are small equiaxed grains in the form of long chains parallel to the solidification direction and are located on the surface of the casting. Freckles decrease the mechanical properties of DS and SX blades; therefore, they should be always unambiguously identified to improve the manufacturing process. This work presents the possibilities of identifying and evaluating freckles in DS casting made of PWA 1426 superalloy by combining the scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and electron backscatter diffraction (EBSD) techniques.

Analyses of The Eutectoid Phase Transformation in Complex Ds Nb-Silicide In-Situ Composites

2001 ◽  
Vol 7 (S2) ◽  
pp. 1244-1245
Author(s):  
S.D. Sitzman ◽  
B.P. Bewlay
Keyword(s):  
Crystal Structure ◽  
Pattern Analysis ◽  
Electron Backscatter Diffraction ◽  
Czochralski Method ◽  
Directionally Solidified ◽  
Two Phase ◽  
In Situ Composites ◽  
Structural Applications ◽  
Backscatter Diffraction

In-situ composites based on (Nb) and Nb silicides, such as Nb5Si3 (tI32 crystal structure) and Nb3Si (tP32 crystal structure), are being investigated for revolutionary high-temperature structural applications [1,2]. The use of Hf and Ti alloying additions to these silicides has also been examined; in these systems Nb5Si3 has also been observed with the hP16 structure. The present paper describes EBSD analyses of a directionally solidified (DS) Nb-silicide based composite that experienced a eutectoid transformation. The composites were directionally solidified using the Czochralski method as described previously [1]. The composites were creep tested at 1200°C for 24 hours. Microstructure and microtexture characterization were performed using scanning electron microscopy, and electron backscatter diffraction pattern analysis (EBSD).The microstructure of a composite directionally solidified from a Nb-12.5Hf-33Ti-16Si alloy is shown in Figure 1. in the as-DS condition the microstructure consisted of primary (Nb)3Si dendrites and coarse (Nb)3Si-(Nb) two-phase cells.

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