scholarly journals Comparative Study of Microstructural Characteristics and Hardness of β-Quenched Zr702 and Zr–2.5Nb Alloys

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3752 ◽  
Author(s):  
Jiahong Dai ◽  
Haotian Guan ◽  
Linjiang Chai ◽  
Kang Xiang ◽  
Yufan Zhu ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Electron Backscatter Diffraction ◽  
Microstructural Characteristics ◽  
Plate Structures ◽  
Average Width ◽  
Before And After ◽  
Quantitative Analyses ◽  
Backscatter Diffraction ◽  
Equiaxed Grains ◽  
Misorientation Angles

In this study, two commercial Zr alloys (Zr702 and Zr–2.5Nb) were subjected to the same β-quenching treatment (water cooling after annealing at 1000 °C for 10 min). Their microstructural characteristics and hardness before and after the heat treatment were well characterized and compared by electron channel contrast (ECC) imaging, electron backscatter diffraction (EBSD) techniques, and microhardness measurements. Results show that after the β quenching, prior equiaxed grains in Zr702 are transformed into Widmanstätten plate structures (the average width ~0.8 μm) with many fine precipitates distributed along their boundaries, while the initial dual-phase (α + β) microstructure in Zr–2.5Nb is fully replaced by fine twinned martensitic plates (the average width ~0.31 μm). Differences in alloying elements (especially Nb) between Zr702 and Zr–2.5Nb are demonstrated to play a key role in determining their phase transformation behaviors during the β quenching. Analyses on crystallographic orientations show that the Burgers orientation relationship is well obeyed in both the alloys with misorientation angles between α plates essentially focused on ~60°. After β quenching, the hardnesses of both alloys were increased by ~35%–40%. Quantitative analyses using the Hall–Petch equation suggest that such an increase was mainly attributable to phase transformation-induced grain refinements. Since Nb is able to effectively refine the β-quenched structures, a higher hardness increment is produced in Zr–2.5Nb than in Zr702.

scholarly journals EBSD-Based Techniques for Characterization of Microstructural Restoration Processes during Annealing of Metals Deformed to Large Plastic Strains

2012 ◽  
Vol 715-716 ◽  
pp. 203-210 ◽  
Author(s):  
Andrew Godfrey ◽  
O.V. Mishin ◽  
T.B. Yu
Keyword(s):  
Equal Channel Angular Extrusion ◽  
Electron Backscatter Diffraction ◽  
Dislocation Cell ◽  
Plastic Strains ◽  
High Angle ◽  
Microstructural Refinement ◽  
Before And After ◽  
Backscatter Diffraction ◽  
Misorientation Angles

Some methods for quantitative characterization of the microstructures deformed to large plastic strains both before and after annealing are discussed and illustrated using examples of samples after equal channel angular extrusion and cold-rolling. It is emphasized that the microstructures in such deformed samples exhibit a heterogeneity in the microstructural refinement by high angle boundaries. Based on this, a new parameter describing the fraction of regions containing predominantly low angle boundaries is introduced. This parameter has some advantages over the simpler high angle boundary fraction parameter, in particular with regard to data collected from electron-backscatter diffraction investigations, where boundaries with very low misorientation angles cannot be reliably detected. It is shown how this parameter can be related to the recrystallization behavior. Another parameter, based on mode of the distribution of dislocation cell sizes is outlined, and it is demonstrated how this parameter can be used to investigate the uniformity, or otherwise, of the restoration processes occurring during annealing of metals deformed to large plastic strains.

Analysis and characterization by electron backscatter diffraction of microstructural evolution in the adiabatic shear bands in Fe–Cr–Ni alloys

2009 ◽  
Vol 24 (8) ◽  
pp. 2617-2627 ◽  
Author(s):  
Huajie Yang ◽  
Yongbo Xu ◽  
Yasuaki Seki ◽  
Vitali F. Nesterenko ◽  
Marc André Meyers
Keyword(s):  
Microstructural Evolution ◽  
Electron Backscatter Diffraction ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
Adiabatic Shear Bands ◽  
Localized Deformation ◽  
Ni Alloys ◽  
Electron Backscatter ◽  
Backscatter Diffraction ◽  
Equiaxed Grains

The microstructural evolution inside adiabatic shear bands in Fe–Cr–Ni alloys dynamically deformed (strain rates > 104 s−1) by the collapse of an explosively driven, thick-walled cylinder under prescribed strain conditions was examined by electron backscatter diffraction. The observed structure within the bands consisted of both equiaxed and elongated grains with a size of ∼200 nm. These fine microstructures can be attributed to recrystallization; it is proposed that the elongated grains may be developed simultaneously with localized deformation (dynamic recrystallization), and the equiaxed grains may be formed subsequently to deformation (static recrystallization). These recrystallized structures can be explained by a rotational recrystallization mechanism.

Effects of Anisotropy on the Microstructural Characteristics and Mechanical Behavior of Shock-Loaded of AZ31 Alloy

2011 ◽  
Vol 284-286 ◽  
pp. 1537-1541 ◽  
Author(s):  
Min Hao ◽  
Fan Zhang ◽  
Cheng Wen Tan ◽  
Tie Jian Su ◽  
Xiao Dong Yu
Keyword(s):  
Mechanical Behavior ◽  
Strain Hardening ◽  
Electron Backscatter Diffraction ◽  
Az31 Alloy ◽  
Peak Strain ◽  
Compression Tests ◽  
Microstructural Characteristics ◽  
Post Shock ◽  
Backscatter Diffraction ◽  
Strain Hardening Rate

Effects of anisotropy on the microstructural characteristics and mechanical behavior of shock loaded of AZ31 magnesium alloy have been investigated. Using electron backscatter diffraction, tension twinning was observed in both shock loading directions along the normal (ND) and rolling directions (RD). Compression tests were carried out along ND and RD in both as-received and post-shock conditions. It indicated that the RD samples show a more notable hardening behavior compared to the as-received conditions. Moreover, it is postulated here that detwinningresults in a drop of strain-hardening rate for the ND samples under post shock reload conditions and tension twinning formed during the shock wave loading process leads to a significant moving left of the peak strain hardening rate for the RD samples under post shock reload conditions.

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).

The Spectrum of Crystallographic Misorientations of Intercrystalline Boundaries for BCC-HCP Phase Transformation in Additively Manufactured Ti-6Al-4V

2021 ◽  
Vol 410 ◽  
pp. 867-871
Author(s):  
Andrey A. Redikultsev ◽  
Stepan I. Stepanov ◽  
Mikhail L. Lobanov
Keyword(s):  
Electron Backscatter Diffraction ◽  
Experimental Spectrum ◽  
High Angle ◽  
Structural And Phase Transformations ◽  
Orientation Microscopy ◽  
Α Phase ◽  
Interphase Boundaries ◽  
Intercrystalline Boundaries ◽  
Backscatter Diffraction ◽  
Misorientation Angles

Electron backscatter diffraction is a modern experimental method for local structure and texture investigation, which makes it possible to establish the presence and types of the various boundaries between the elements of the mesostructure such as low or high angle, special and interphase boundaries. Moreover, this technique can demonstrate the migration of boundaries during structural and phase transformations. This study estimated the possible spectrum of crystallographic misorientations of intercrystalline boundaries in additively manufactured titanium alloy Ti-6Al-4V using orientation microscopy and crystallographic calculations based on Burgers orientation relationship during β→α-transformation. The study has established that the boundaries between grains of α-phase are characterized by the misorientation angles of 11±2 °, 61±5 °, 89±3 °. The majority of high-angle boundaries are characterized by misorientation angles in the range of 57-65 °. The study also ascertained that the experimental spectrum of intercrystalline boundaries in the α-phase reveals the displacive nature of β→α-transformation in titanium alloys.

Workability of ZK60A Alloy Depending on Microstructure

2012 ◽  
Vol 217-219 ◽  
pp. 373-376 ◽  
Author(s):  
K.H. Jung ◽  
Yong Bae Kim ◽  
Byung Min Ahn ◽  
Sang Mok Lee ◽  
Jong Sup Lee ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Uniaxial Compression ◽  
Microstructural Evolution ◽  
Elevated Temperatures ◽  
Electron Backscatter Diffraction ◽  
Strain Rates ◽  
Compression Tests ◽  
Electron Backscatter ◽  
Before And After ◽  
Backscatter Diffraction

In this study, the variation of workability of semi-continuously casted and extruded ZK60A magnesium alloy was investigated. To determine the deformation capability of two different billets, uniaxial compression tests were conducted at elevated temperatures and two different strain rates. In addition, the microstructural evolution was investigated using electron backscatter diffraction (EBSD) to compare the microstructure before and after the extrusion. The formability of ZK60A depending on the microstructure is discussed based on the experimental results obtained in this study, and is compared with earlier research in the literature.

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.

Microstructural Analysis of Biomedical Co-Cr-Mo Alloy Subjected to High-Pressure Torsion Processing

2014 ◽  
Vol 616 ◽  
pp. 263-269
Author(s):  
Murat Isik ◽  
Mitsuo Niinomi ◽  
Ken Cho ◽  
Masaaki Nakai ◽  
Junko Hieda ◽  
...  
Keyword(s):  
High Pressure ◽  
Vickers Hardness ◽  
High Strain ◽  
High Pressure Torsion ◽  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Equivalent Strain ◽  
Ε Phase ◽  
Backscatter Diffraction ◽  
Equiaxed Grains

The effect of high-pressure torsion (HPT) processing on the microstructure and Vickers hardness of Co-Cr-Mo (CCM) alloys were investigated in this study. The microstructure of initial CCM alloy contains equiaxed grains with a grain diameter of approximately 50 μm and twins. The clear grain boundaries of equiaxed grains and twins disappear after HPT processing at a rotation number, N, of 10. The phase maps of initial CCM alloy and CCM alloy subjected to HPT processing at N = 5 measured by electron backscatter diffraction exhibit that the ratio of γ phase decreases from 93.5% to 34.1% and the ratio of ε phase increases from 6.5% to 65.9% by applying HPT processing. These results indicate that the ε phase is formed by high-strain, which is induced by the HPT processing. The Vickers hardness values on the surfaces of the CCM alloys subjected to HPT processing at N = 1, 5, and 10 increase with increasing the equivalent strain, εeq. These results suggest that an increase of Vickers hardness is correlated to an increase of the ratio of ε phase and the dislocation density, and grain refinement, which are caused by the high-strain induced by HPT processing.

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