Electron Backscatter Diffraction Data Research Articles

Crystallographic preferred orientations and microtexture of the Himalayan eclogites revealing records of syn-deformation peak metamorphic stage and subsequent exhumation

Electron backscattered diffraction (EBSD) and crystallographic preferred orientations (CPO) studies on Himalayan high- and ultrahigh-pressure eclogites are reported. Subduction-related peak eclogite facies (omphacite, garnet, quartz, rutile) and exhumation-related post-eclogite facies (hornblende, epidote, titanite) minerals were investigated to understand subduction and exhumation-related deformation regimes. Petrographic features from the studied eclogite samples show preferably shape-oriented omphacites coexisting with random to weakly shape-oriented garnets, and overgrown by hornblende and symplectites. Quartz grains are also randomly shape-oriented in the eclogite matrix whereas epidote grains display shape-preferred orientations. Based on EBSD data, an L-type CPO was dominant in omphacites in the studied eclogites, exhibited by the maximum density of [001] axes parallel to the lineation and the high density of poles to the (010) and (110) planes forming girdles perpendicular to the foliation. This CPO likely developed in a constrictional strain regime during the peak eclogite-facies conditions due to dislocation creep and is associated with an intra-crystalline (110) [001] and (110) <110> slip systems. EBSD data of garnets exhibit complex fabric, suggesting they most likely behaved like rigid objects in the presence of omphacite, indicating insignificant plastic deformation. EBSD data of quartz in high-pressure eclogites show irregular CPO but in ultrahigh-pressure eclogites the fabric is relatively strong. EBSD data of rutile show CPO of [001] axes strongly aligned along the lineation, suggesting its deformation was coeval to the omphacite. Titanite, mainly overgrown around rutile, indicates a random CPO different from rutile, suggesting its growth during late-stages. Hornblende in both types of eclogites shows identical fabric to that of omphacite, displaying CPO of [001] axes parallel to the lineation and poles of (010) and (110) planes form girdles perpendicular to the foliation, suggesting topotactic replacement over omphacite during exhumation. The EBSD data, combined with textural features, indicate syn-deformation peak metamorphism as well as preserve records of subsequent exhumation.

Simulation of the Rheological Behavior and Dynamic Recrystallization of the Heterogenized V95 (7075) Alloy

In this paper, a structural hierarchical viscoplastic model is identified. The model describes the flow stress and the evolution of the microstructure of the heterogenized V95 alloy (the Russian analogue of the 7075 alloy) at a temperature of 400°C in strain rates ranging between 0.01 and 5 s−1. The model describes alloy hardening through increasing dislocation density and softening due to dynamic recovery and recrystallization. The model parameters responsible for dynamic recrystallization are identified by electron backscattered diffraction data. The identification results testify that, at a time-varying strain rate, the model determines the value of flow stress and the amount of dynamic recrystallization with an average relative deviation of 4.2 and 7.6%, respectively. The model is used to obtain the strain rate and strain dependences of the amount of dynamic recrystallization, as well as to plot flow stress curves for strain rates ranging between 0.01 and 5 s−1. The simulation results have allowed us to establish that, with the same accumulated strain level, an increase in the strain rate of the V95 alloy at a temperature of 400°C leads to an increase in the portion of dynamically recrystallized grains. Dynamic recrystallization has a noticeable effect on the shape of the flow stress curve at strain rates exceeding 0.5 s−1, when a pronounced peak appears in the flow stress curves.

Effect of Double-Quenching on the Hardness and Toughness of a Wear-Resistant Steel

Martensitic/bainitic wear-resistant steels are widely used in civilian industry, where a good combination of strength and toughness is required. In the present study, a double-quenching process was applied and compared to the conventional single-quenching process. The microhardness and ductile–brittle transition temperature were measured, and the microstructure was characterized with scanning electron microscopy and electron backscatter diffraction (EBSD) technique. It was found that the double-quenching process refined the prior austenite grain size by 43% and simultaneously improved the toughness and hardness. The ductile-to-brittle transition temperature was decreased from −77 °C to −90 °C, and the hardness was increased by 8%. Based on the EBSD data, a detailed analysis of the grain boundary distribution was performed using a recently developed machine learning model. Unlike what was found in previous studies, for the studied wear-resistant steel, the refinement of the prior austenite grain did not increase the block boundary density while increasing the high-angle packet boundary density. As a result, the total density of the high-angle grain boundaries in the double-quenched specimen was not improved compared to the single-quenched specimen. Further inspection suggested that it is the prior austenite grain boundaries and high-angle packet boundaries that contribute to the hardness and toughness, and the key factors that determine their effectiveness are the high misorientation angle between the {110} slip planes and the high slip transmission factor.

W-Doping of Dense NMC811 Hydroxide through Wet-Impregnation and Its Impact on Crystal Structure, Phase Transition Related Gas Evolution and Electrochemical Performance at Elevated Upper Cut-Off Voltage

Doping of Ni-rich LNMC cathode materials with tungsten via solid-state route has been shown to stabilize the materials against structural degradation at high voltages during electrochemical cycling. Here we use a wet-chemical doping method to homogeneously introduce 0.5 mol% tungsten into dense NMC811 (Li[(Ni0.8Mn0.1Co0.1)]O2), followed by a detailed structural and electrochemical characterization. A homogeneous distribution of W in the materials was evidenced by elemental mapping and TOF-SIMS. The increase in bond-dissociation energy to oxygen (BDEO) of the transition metal (TM) site led to compressed slab thickness (TMO6 octahedron width in c-direction), indicating shorter, and thus strengthened, TM–O bonds, as also confirmed by TGA-MS results. Importantly, statistical analysis of electron backscatter diffraction (EBSD) data revealed a W-induced radial alignment of a–b planes of the primary particles. The cycling stability of the doped material was more than 7% higher for the W-doped (92.4%) as compared to the undoped NMC811 (85.3%) material at a higher upper cut-off voltage of 4.5 V vs Li/Li+. Furthermore, the voltage decay was lower (0.2 V vs 0.29 V), leading to >2% lower energy loss (5.3% vs 7.4%) for the W-doped material.

Effect of distribution characters of ferrite/bainite on deformation compatibility in dual-phase pipeline steel: Experimental and numerical study

The morphology distribution of microstructure has an important influence on the match of the strength and plasticity of dual-phase pipeline steel. Bainite and PF dual-phase steels with layered and network morphology were obtained by combining the Thermomechanical Control Process (TMCP) and inter-critical isothermal heat treatment. A novel experimental-numerical methodology studied the effect of phase distribution characters on the deformability of PF and bainite dual-phase pipeline steel. The plastic damage features and microscopic strain and stress distribution in both network and layered microstructure were clarified. The obvious differences in the microstructure evolution for both samples were captured by a quasi-situ tensile test. The PF phase in the network morphology sample was believed the main deformation phase, but the deformation of the PF phase in the layered morphology sample was restrained. Two three-dimensional (3D) crystal plasticity finite element models (CPFEMs) were established based on the electron backscatter diffraction (EBSD) data. The simulation results indicated that the strain field in layered microstructure was more uniform than that in network microstructure, and the continuous internal stress relaxation (ISR) in the bainite phase led to plastic damage at low tensile strain level; The strain field in network microstructure mainly existed in the PF phase, the deformation of the PF phase can be fully utilized. When changing the tensile x-direction of the layered microstructure to the z-direction, the strain field showed an obvious anisotropy, and loading in the z-direction increased the risk of interlaminar crack formation. • Quasi-situ tensile test was used to study the deformation behavior • Strain/stress distribution characteristics were clarified using CPFEM method • Uniform strain distribution and ISR in layered microstructure decreased its plasticity • z-axis loading increased the risk of interlaminar crack for layered microstructure

Experimental Investigation on the Inhomogeneities of Transverse Microstructure and Internal Stress of High‐Strength Low‐Alloy Hot‐Rolled Strip

Herein, the evolution of transformation in the width direction of high‐strength low‐alloy hot‐rolled strip is studied by using thermomechanical simulation, and the temperature, microstructure, and internal stress are correlated based on electron backscatter diffraction data. The temperature and time range of the transverse transformation are determined based on the thermal expansion curve. The results show that the transformation at the edge of the steel plate ends earliest and that at the plate center begins at the latest; only 31.9% austenite undergoes transformation at the plate central by the end of laminar cooling. The fraction of transformed austenite at the plate center is the least throughout the laminar cooling process. The proportion of small grains (within the grain size range of 0–4 μm), mean, and variant coefficient of grain sizes at the plate edge are 75%, 4 μm, and 1.29, respectively. In contrast, those values of the central region are 66%, 4.4 μm, and 1.05, respectively. The correlation between temperature and internal stress evolutions is established. It is demonstrated that the internal stress increases monotonically with the average transformation rate.

Two-step deformation-induced martensitic transformation in additively manufactured High-Si stainless steel

Deformation-induced phase transformation in the additively manufactured (AM) Fe–18Cr–8Ni-5.5Si (in wt.%) alloy was analyzed using the in-situ electron backscattered diffraction (EBSD) record during uniaxial tensile testing in a scanning electron microscope (SEM). Analysis of EBSD data was focused to investigate phase transformation behavior during deformation with consideration of mechanical interactions among phases and grains in the ultrafine AM microstructure. The initial EBSD phase map illustrated that the as-built microstructure was a duplex structure consisting of major austenite (γ) and minor ferrite phases, some of which showed non-traditional orientation relationship since the rapid solidification in the AM process has produced non-equilibrium state in phase formation. In the deformed as-built AM alloy, the two-step martensitic transformation (γ→ε→α′) was identified as the main deformation-induced transformation mechanism. Martensitic transformation steps were found to be associated with glides of Shockley partial dislocations on closed packed (111) planes under the influence of atomic disturbance in the γ and ε phases, respectively. Using the closed-packed plane pole figures and unit cell orientations, their evolutions and mechanisms accompanying with the transformation were analyzed. The results indicate that one variant of ε-martensite forms from their parent γ phase, while two variants of α′ form from their parent ε phase.

Correlated subgrain and particle analysis of a recovered Al-Mn alloy by directly combining EBSD and backscatter electron imaging

Correlated analysis of (sub)grains and particles in alloys is important to understand transformation processes and control material properties. A multimodal data fusion workflow directly combining subgrain data from electron backscatter diffraction (EBSD) and particle data from backscatter electron (BSE) images in the scanning electron microscope is presented. The BSE images provide detection of particles smaller than the applied step size of EBSD down to 0.03 μm in diameter. The workflow is demonstrated on a cold-rolled and recovered Al-Mn alloy, where constituent particles formed during casting and dispersoids formed during subsequent heating affect recovery and recrystallization upon annealing. The multimodal dataset enables statistical analysis including subgrains surrounding constituent particles and dispersoids' location with respect to subgrain boundaries. Among the subgrains of recrystallization texture, Cube{001}〈100〉 subgrains experience an increased Smith-Zener drag from dispersoids on their boundaries compared to CubeND{001}〈310〉 and P{011}⟨5¯6¯6⟩ subgrains, with the latter experiencing the lowest drag. Subgrains at constituent particles are observed to have a growth advantage due to a lower dislocation density and higher boundary misorientation angle. The dispersoid size per subgrain boundary length increases as a function of misorientation angle. The workflow should be applicable to other alloy systems where there is a need for analysis correlating grains and grain boundaries with secondary phases smaller than the applied EBSD step size but resolvable by BSE imaging.

Microstructure, deformation and fracture mechanisms in Al-4043 alloy produced by laser hot-wire additive manufacturing

High deposition rate additive manufacturing (AM) processes with minimal feedstock costs are desirable to reduce part fabrication times and minimize the cost of implementation. Wire-based AM processes meet these demands but suffer from higher heat inputs that can lead to thermal distortion and large heat-affected zones neighboring the melt pools. Here, the tensile deformation response of an Al 4043 (Al-Si) alloy deposited on an Al 6061-T6 substrate using a laser hot-wire AM process was investigated. Digital image correlation during tensile testing was combined with optical microscopy and electron backscatter diffraction data to understand the deformation mechanisms that occurred in samples from a deposited wall in the as-built condition. During tensile testing, localized deformation was observed at the melt pool boundary regions that correlated with serrations on the stress-strain curve. The primary aluminum dendrites in regions adjacent to the melt pool boundary regions were coarser than in bulk deposited material, leading to localized deformation of the coarser microstructure. EBSD post-test analysis confirmed that the accumulated strains had occurred in the melt pool boundary regions. Analysis of the thermal and solidification conditions in the melt pool indicated that the coarsened region was associated with partial remelting of the eutectic phase. This understanding of deformation mechanisms associated with the inhomogeneities at melt pool boundaries can enable AM-specific considerations for improved process and alloy design, particularly for eutectic alloys. • Al 4043 parts were deposited using laser hot-wire additive manufacturing. • The deposited Al 4043 had similar mechanical properties to arc-based AM. • DIC during tensile testing revealed serrated flow resulting from localized deformation. • Partial remelting of the eutectic near the melt pool boundary resulted in coarser dendrites than bulk regions. • Localized deformation was correlated with the coarser microstructure near the melt pool boundary.

Deformation induced decoupling between U-Pb and trace elements in titanite revealed through petrochronology and study of localized deformation

In this contribution, we analyzed a pair of mafic samples collected from a recently identified shear zone and its proximal footwall from the Manicouagan Imbricate Zone (MIZ) of the central Grenville Province, Québec, Canada. Titanite petrochronology, metamorphic phase equilibria modelling, trace element thermometry, and electron backscattered diffraction data were used to define a Pressure-Temperature-time-Deformation path for the two samples. An interconnected dislocation network within titanite grains, as outlined with Kerneled Average Misorientation maps, are spatially correlated with variation in the U-Pb system but not with that observed for trace element These results suggest that the U-Pb system was decoupled from trace and rare earth elements and that deformation, rather than interface-coupled dissolution-precipitation reactions or re-crystallisation, was the main driver for this decoupling. In addition to highlighting a potential pitfall of titanite petrochronology, our P-T-t-D path reveals that ductile shear zones were active later than previously suggested within the MIZ.

Effects of GNPs on variant selection during quenching of Ti6Al4V matrix composites prepared by hot extrusion

In this work, Ti–6Al–4V matrix composites with GNPs distributed along the extrusion direction(ED) were prepared by hot extrusion, and the effect of GNPs on variant selection of Ti6Al4V alloy during quenching was investigated. The electron backscatter diffraction (EBSD) data showed that GNPs induced variant selection of Ti–6Al–4V, resulting in a difference in the texture intensity distribution of basket-woven α phase in the transverse direction (TD). The contents of various variants in a single grain were analyzed statistics, and the volume changes caused by the variants were calculated. The results show that the interfacial stress of GNPs increases the content of α variants whose volume expansion direction is consistent with the expansion direction of GNPs.

Crystal plasticity enhances trace element mobility in garnet

Abstract Chemical heterogeneities along grain boundaries in garnet occur across a wide range of metamorphic conditions, yet the processes underlying their development remain poorly understood. Here we integrate electron backscattered diffraction (EBSD) and atom probe tomography (APT) to evaluate the mechanisms driving nanoscale trace element mobility to deformation microstructures in a granulite-facies garnet. This approach shows that low-angle boundaries can be enriched in Ca, Ti, P, Cu, K, Na, Cl, and H. Based on the correlation between EBSD and APT data, we propose that solute ions (Ca, Ti, P, and Cu) were segregated to the interface during the migration of dislocation associated with ductile deformation of the grain. In contrast, elements such as K, Na, Cl, and H are interpreted to reflect diffusion along the low-angle boundary from an externally derived fluid source. These results provide the missing link between chemical heterogeneity and deformation-related microstructures in garnet. Our approach shows that a combination of microstructural and nanoscale geochemical analyses can provide unprecedented insights into mechanisms of element transfer within minerals.

Single crystal elastic constants of additively manufactured components determined by resonant ultrasound spectroscopy

Bayesian inference with Sequential Monte Carlo was used to determine the single crystal elastic constants of additively manufactured (AM) cobalt‑nickel-based superalloy specimens from only the resonant frequencies and texture data. This novel framework enables the quantification of the single crystal elastic constants for AM and polycrystalline specimens using only electron backscatter diffraction (EBSD) and Resonant Ultrasound Spectroscopy (RUS), avoiding the expense of bulk single crystal fabrication or synchrotron experiments. A parallelizable and open-source Python package (SMCPy) was used to perform Bayesian inference of the single crystal elastic constants from resonant frequencies of AM specimens. The single crystal elastic constants determined from AM cobalt‑nickel-base superalloy specimens were validated with measurements of the single crystal elastic constants on a bulk single crystal specimen. EBSD texture data was used to determine the single crystal elastic constants from the resonant frequencies of AM specimens, and validated with neutron diffraction data by considering the experimental uncertainty in both the EBSD and neutron diffraction data. The robustness of this framework for varied texture orientations relative to the build direction (BD) was demonstrated for AM specimens printed at 0° and 20° BD-inclinations. • Single crystal elastic constants are determinable with RUS/ EBSD of AM specimens. • Textures both aligned and misaligned to BD are demonstrated. • Single crystal constant variability driven by error in input texture coefficients. • Parallelized SMC enables 10× computation time reduction.

Assessment of the post-dynamic recrystallization effects on the overall dynamic recrystallization kinetics in a Ni-base superalloy

Understanding the role of microconstituents, viz., precipitates, and carbides, on dynamic recrystallization (DRX) and on post-dynamic recrystallization (PDRX) is essential to obtain a uniform microstructure with desirable grain size during hot deformation. Thus, the present study was taken up to address the role of carbides on DRX as well as on the PDRXcharacteristics of a Ni-base superalloy XH55 (Ni-17Cr-12Fe-9Mo-2 Nb-1.8Al-0.04 C). Uniaxial hot compression tests were conducted in the temperature range of 950–1100 °C and at a constant strain rate of 10−1 s−1 on the peak-aged specimens. The evolution of DRX without and with post-deformation hold for 15 s was correlated with the flow softening mechanisms across the tested temperature range. Besides, the PDRX fraction and its evolution with temperature was estimated from the electron backscattered diffraction data while using the denoising filters and a grain level misorientation parameter. Further, intermittent post-deformation microstructural characterization was carried out on the specimens deformed at 1050 °C to understand the role of carbides in the initial stages of DRX and PDRX. Overall, the present study illustrates that carbides have inhibited the DRX kinetics in the initial stage, i.e., at low strains (ε<0.40). Whereas, at higher strains (ε>0.40), the role of carbides is limited in inhibiting the growth of the recrystallized (DRX and PDRX) grains present in their vicinity.

Investigation of microstructure and mechanical properties of Cu-Ni alloy processed by equal channel angular pressing

The Copper-Nickel alloy, C70600, was subjected to severe plastic deformation by the equal channel angular pressing (ECAP) technique. The material was pressed at room temperature along route BC for eight passes. Microstructural analysis and mechanical characterization of the material were done for each of the ECAP pass samples. The initial homogenized material having equiaxial grains of average grain size 75 µm was reduced to 20 µm after eight ECAP passes. Electron backscatter diffraction data presented an increase in low angle grain boundaries with an increase in the number of ECAP passes. Initially, the ultimate tensile strength and the hardness increased by 56% and 94% respectively. After the fifth ECAP pass, a drastic reduction in ultimate tensile strength and ductility was witnessed. Hardness value remained constant after the fifth ECAP pass. Fractography analysis indicate the ductile mode of fracture with reduced dimple size at higher ECAP passes.

Effect of Phase-Selective Nanoscale Precipitates on the Bauschinger Effect in Austenitic–Ferritic Duplex Stainless Steels

The Bauschinger effect in austenitic–ferritic duplex stainless steel 1.4462 was investigated using tension–compression tests combined with electron backscatter diffraction (EBSD). A major focus was on the impact of phase-selective nanoscale α′ precipitates formed in the ferritic phase due to 475 °C embrittlement. Contrary to the general knowledge that coherent precipitates have only a short-range effect and thus no significant influence, a strong increase in the Bauschinger effect was detected. Based on EBSD data and cyclic micro-indentations in individual grains, it was demonstrated that α′ precipitates enhance the phase difference between austenite and ferrite and increase deformation incompatibility and local dislocation density gradients at phase boundaries. Thus, despite their small size and coherence, α′ precipitates lead to long-range back stresses that significantly enhance the Bauschinger effect. In addition, the influence of precipitation was shown to depend on the extent of pre-strain during initial loading. The insights demonstrate that the influence of precipitates on the Bauschinger effect is highly complex and always needs to be analyzed with respect to precipitation characteristics, microstructure, and external boundary conditions.

On Σ9 grain boundary plane orientation

Past measurements of the orientation of the ∑9 grain boundary plane have consistently shown that it adopts a tilt orientation. However, in different circumstances, a wide range of symmetric and asymmetric tilt boundaries are observed. Here, a stereological interpretation of electron-backscatter diffraction data was used to measure the orientation of the ∑9 grain boundary plane in Fe-30Ni. The grain boundary plane orientation was found to be influenced by the types of boundaries meeting the ∑9 at triple points. ∑9 boundaries attached to random high angle boundaries showed a nearly continuous range of symmetric and asymmetric tilt boundaries. ∑9 boundaries attached to ∑3 boundaries selectively adopted a range of lower energy grain boundaries with grain boundary normals between (001) and (11¯1) orientations. As the coherency of the attached ∑3 boundaries increased, the grain boundary plane orientation maximum was found at the (11¯4)//(11¯4) symmetric tilt orientation, thought to be minimum energy for this disorientation. The distribution of ∑9 grain boundary plane orientations depends on the fraction of ∑3 boundaries and how close they are to the coherent twin orientation.

Defect‐Induced Effects in Nanomaterials

Defect‐Induced Effects in Nanomaterials

Using Misorientation and Weighted Burgers Vector Statistics to Understand Intragranular Boundary Development and Grain Boundary Formation at High Temperatures

AbstractDuring plastic deformation, strain weakening can be achieved, in part, via strain energy reduction associated with intragranular boundary development and grain boundary formation. Grain boundaries (in 2D) are segments between triple junctions, that connect to encircle grains; every boundary segment in the encircling loop has a high (&gt;10°) misorientation angle. Intragranular boundaries terminate within grains or dissect grains, usually containing boundary segments with a low (&lt;10°) misorientation angle. We analyze electron backscatter diffraction (EBSD) data from ice deformed at −30°C ( 0.9). Misorientation and weighted Burgers vector (WBV) statistics are calculated along planar intragranular boundaries. Misorientation angles change markedly along each intragranular boundary, linking low‐ (&lt;10°) and high‐angle (10–38°) segments that exhibit distinct misorientation axes and WBV directions. We suggest that these boundaries might be produced by the growth and intersection of individual intragranular boundary segments comprising dislocations with distinct slip systems. There is a fundamental difference between misorientation axis distributions of intragranular boundaries (misorientation axes mostly confined to ice basal plane) and grain boundaries (no preferred misorientation axis). These observations suggest during progressive subgrain rotation, intragranular boundaries remain crystallographically controlled up to large misorientation angles (&gt;&gt;10°). In contrast, the apparent lack of crystallographic control for grain boundaries suggests misorientation axes become randomized, likely due to the activation of additional mechanisms (such as grain boundary sliding) after grain boundary formation, linking boundary segments to encircle a grain. Our findings on ice intragranular boundary development and grain boundary formation may apply more broadly to other rock‐forming minerals (e.g., olivine, quartz).

On the plasticity of a hot-rolled Zircolay-4 via a combination of in-situ acoustic emission and ex-situ EBSD techniques

The plastic anisotropy of a hot-rolled Zircaloy-4 (Zr-1.56Sn-0.22Fe-0.11Cr) occurring during compressive loading in three orthogonal directions was analysed using the acoustic emission (AE) technique and scanning electron microscopy (SEM). In particular, AE was used for in-situ monitoring of the activity of individual deformation mechanisms. The microstructure was characterized by the electron backscatter diffraction (EBSD) technique in the initial state and after deformation of 2% and 12%, respectively. The grain reference orientation deviation (GROD) maps estimated from the EBSD data reveal the evolution of slip system activities in individual grains. During compressive loading along the rolling and transverse directions (RD and TD, respectively), dislocation glide and twinning are dominant deformation mechanisms. Moreover, the AE technique in combination with EBSD analysis indicates that more intensive twinning in RD, reflected by a high twin volume fraction, is rather given by twin thickening than massive twin nucleation. With respect to the initial texture, the twinning is almost suppressed during loading along the normal direction (ND) and plastic deformation is realized by several slip systems, including multiple slip.