scholarly journals Phase Transformation in 316L Austenitic Steel Induced by Fracture at Cryogenic Temperatures: Experiment and Modelling

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 127
Author(s):  
Kinga Nalepka ◽  
Błażej Skoczeń ◽  
Marlena Ciepielowska ◽  
Rafał Schmidt ◽  
Jakub Tabin ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Electron Backscatter Diffraction ◽  
Secondary Phase ◽  
Transition Process ◽  
Primary Phase ◽  
Extended Finite Element ◽  
Steel Microstructure ◽  
Interphase Boundaries ◽  
Synchrotron Studies ◽  
Backscatter Diffraction

Investigations by electron backscatter diffraction (EBSD) and X-ray diffraction with the use of synchrotron radiation, as well as parallel extended finite element (XFEM) simulations, reveal the evolution of the 316L stainless steel microstructure in the vicinity of a macro-crack developing at the temperature of liquid helium (4.2 K). The fracture propagation induces a dynamic, highly localized phase transformation of face-centred cubic austenite into α’ martensite with a body-centred cubic structure. Synchrotron studies show that the texture of the primary phase controls the transition process. The austenite grains, tending to the stable Brass orientation, generate three mechanisms of the phase transformation. EBSD studies reveal that the secondary phase particles match the ordered austenitic matrix. Hence, interphase boundaries with the Pitsch disorientation are most often formed and α’ martensite undergoes intensive twinning. The XFEM simulations, based on the experimentally determined kinetics of the phase transformation and on the relevant constitutive relationships, reveal that the macro-crack propagates mainly in the martensitic phase. Synchrotron and EBSD studies confirm the almost 100% content of the secondary phase at the fracture surface. Moreover, they indicate that the boundaries formed then are largely random. As a result, the primary beneficial role of martensite as reinforcing particles is eliminated.

scholarly journals Visualization of the Bainite Fine Structure Using EBSD and Euler Angles

2019 ◽  
Vol 1 (1) ◽  
pp. 11
Author(s):  
Yu.V. Yudin ◽  
A.A. Kuklina ◽  
M.V. Maisuradze ◽  
M.S. Karabanalov
Keyword(s):  
Fine Structure ◽  
Electron Backscatter Diffraction ◽  
Three Dimensional ◽  
Diffraction Method ◽  
Bainitic Steel ◽  
Near Surface ◽  
Steel Microstructure ◽  
Electron Backscatter ◽  
Backscatter Diffraction ◽  
Ebsd Method

The electron backscatter diffraction method (EBSD) is widely used to studycrystallographic orientational relationships of the steel microstructure constituentsincluding bainite. Nevertheless the fine structure of bainite (subunits, plates) is notinvestigated by this method. In this paper we propose a technique for visualizing ofthe structure of a bainitic steel near-surface layer using the values of Euler anglesobtained by EBSD method. A three-dimensional picture of the bainite fine structure ofthe HY-TUF steel obtained by the proposed technique is in

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.

Characterization of Dual-Phase Steel Microstructure by Combined Submicrometer EBSD and EPMA Carbon Measurements

2013 ◽  
Vol 19 (4) ◽  
pp. 996-1006 ◽  
Author(s):  
Philippe T. Pinard ◽  
Alexander Schwedt ◽  
Ali Ramazani ◽  
Ulrich Prahl ◽  
Silvia Richter
Keyword(s):  
Dual Phase Steel ◽  
Electron Backscatter Diffraction ◽  
Hydrocarbon Contamination ◽  
Dual Phase ◽  
Kernel Average Misorientation ◽  
Steel Microstructure ◽  
Backscatter Diffraction ◽  
Induced Dislocation ◽  
Better Than

AbstractElectron backscatter diffraction (EBSD) and electron probe microanalysis (EPMA) measurements are combined to characterize an industrial produced dual-phase steel containing some bainite fraction. High-resolution carbon mappings acquired on a field emission electron microprobe are utilized to validate and improve the identification of the constituents (ferrite, martensite, and bainite) performed by EBSD using the image quality and kernel average misorientation. The combination eliminates the ambiguity between the identification of bainite and transformation-induced dislocation zones, encountered if only the kernel average misorientation is considered. The detection of carbon in high misorientation regions confirms the presence of bainite. These results are corroborated by secondary electron images after nital etching. Limitations of this combined method due to differences between the spatial resolution of EBSD and EPMA are assessed. Moreover, a quantification procedure adapted to carbon analysis is presented and used to measure the carbon concentration in martensite and bainite on a submicrometer scale. From measurements on reference materials, this method gives an accuracy of 0.02 wt% C and a precision better than 0.05 wt% C despite unavoidable effects of hydrocarbon contamination.

scholarly journals Shock-reshock of zirconium to explore the effect of microstructure on the alpha-omega phase transformation

2021 ◽  
Vol 250 ◽  
pp. 03010
Author(s):  
Benjamin M. Morrow ◽  
Juan P. Escobedo-Diaz ◽  
David R. Jones ◽  
Carl P. Trujillo ◽  
Daniel T. Martinez ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Phase Field ◽  
Electron Backscatter Diffraction ◽  
Peak Stress ◽  
Relative Activity ◽  
Material Behavior ◽  
Omega Phase ◽  
Orientation Relationships ◽  
Final Microstructure ◽  
Backscatter Diffraction

Phase transformations play an important role in the mechanical behavior of materials subjected to extreme loading conditions. A series of shock-reshock experiments were fielded to determine whether the phase transitions in materials are significantly enhanced or inhibited by preexisting microstructural features. Polycrystalline zirconium samples were shock loaded using gas-gun plate impact and soft recovered to examine microstructure using electron backscatter diffraction (EBSD). Drive conditions were varied to study the (hcp) alpha to (hexagonal) omega solidsolid phase transformation. Recovered samples were then subjected to a second shock loading event to determine the change in material behavior as a function of pre-shock microstructure. Crystallography of phase fragments in the final microstructure showed that prior twinning (formed during the shock to a peak stress below the transition threshold) appeared to suppress omega formation/retention after reshock. Conversely, when a material was initially shocked into the omega phase field, retained-omega was not found to have a large impact on subsequent omega formation during reshock. This suggests that nucleation and growth of omega phase are important processes, and the relative activity of nucleation vs. growth processes is modified by a pre-existing substructure. Additionally, orientation relationships reveal a reverse transformation pathway (omega to alpha) dominates the final microstructure, suggesting significant grain growth in the omega phase field is possible even for dynamic timescales.

Supersaturation and solute enrichment and their role in phase transformations in metal alloys

2011 ◽  
Vol 83 (5) ◽  
pp. 1085-1092 ◽  
Author(s):  
Markus Rettenmayr
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Single Phase ◽  
Driving Forces ◽  
Secondary Phase ◽  
Transformation Process ◽  
Primary Phase ◽  
Two Phase ◽  
Phase Mixture ◽  
Phase Out

Supersaturations and depletion or enrichment of solute/solvent are known to be the driving forces for phase transformations. In the present work, a series of different experiments is presented where in a single phase or a two-phase mixture supersaturation or enrichment/depletion of solute occur in at least one of the phases. In all cases the result is a phase transformation, particularly either the precipitation of a secondary phase out of a primary phase, or the migration of the interface in a two-phase mixture. It is demonstrated that solute transport in the phase exhibiting faster kinetics controls the phase transformation process.

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.

Thermomechanical behavior and microstructural evolution in tantalum thin films

2004 ◽  
Vol 854 ◽  
Author(s):  
Robert Knepper ◽  
Katherine Jackson ◽  
Blake Stevens ◽  
Shefford P. Baker
Keyword(s):  
Phase Transformation ◽  
Grain Growth ◽  
Electron Backscatter Diffraction ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Tensile Direction ◽  
Grain Sizes ◽  
Curvature Measurement ◽  
Backscatter Diffraction

ABSTRACTTa films were prepared in the metastable β phase using an ultra-high vacuum sputter deposition system. The stresses that arose during thermal cycles to 750°C were measured using an in situ substrate curvature measurement system, allowing oxygen content in the films to be minimized. A phase transformation from β to the stable α phase takes place in conjunction with distinct “jumps” in stress in the tensile direction during heating at approximately 400°C and 650°C. X-ray and electron backscatter diffraction (EBSD) analyses were used to determine grain sizes, along with crystal phase and orientation information. These results indicate a significant amount of grain growth accompanying the phase transformation. It is found that the measured total stress change is in reasonable agreement with that predicted by the combination of grain growth, crystal densification associated with the phase transformation, and stress relaxation.

scholarly journals Investigation of the α−γ−α Phase Transformation in Steel: High-Temperature In Situ EBSD Measurements

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
I. Lischewski ◽  
D. M. Kirch ◽  
A. Ziemons ◽  
G. Gottstein
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Electron Backscatter Diffraction ◽  
Experimental Setup ◽  
Ebsd Data ◽  
Α Phase ◽  
Electron Backscatter ◽  
First Results ◽  
Backscatter Diffraction

A newly developed laser powered heating stage for commercial SEMs in combination with automated established electron backscatter diffraction (EBSD) data acquisition is presented. This novel experimental setup can be used to achieve more information about microstructure and orientation changes during grain growth, recrystallization, recovery, and phase transformations. First results on the α−γ−α phase transformation in steel within 886∘C–900∘C are presented.

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