bluuebunny/crossref_metadata_2025_split huggingface dataset:
Monitoring microstructural evolution in-situ during cyclic loading with high-resolution reciprocal space mapping
Authors: Diederichs Annika Martina , Lienert Ulrich , Pantleon Wolfgang 
Published: December 2019

Abstract
High-resolution reciprocal space mapping using high-energy hard x-rays has been developed to investigate the microstructure of grains located in the bulk of a metallic sample in a non-destructive way in-situ during different loading conditions. The technique allows to identify and follow individual grains and subgrains during ongoing deformation such as loading in tension and compression, during repeated cyclic deformation or even individual load cycles while simultaneously monitoring macroscopic stress and strain. Insight in the structural reorganization within single grains is gained by in-situ monitoring of the characteristic intensity distribution of Bragg reflections from individual grains during cyclic deformation of commercially pure polycrystalline aluminium. By reciprocal space mapping with high angular resolution and combined analysis of the radial and azimuthal information, individual subgrains are tracked during single load cycles with different strain amplitudes. Additionally, changes in mean peak position, peak width and asymmetry of integrated radial profiles from individual grains are analyzed as well as their orientation spread. In this manner, the microstructural evolution in grains embedded in the bulk of polycrystalline specimens is traced and linked to the changing mechanical loads during cyclic deformation.
Roles of transformation interfaces in the design of advanced high strength steels
Authors: Furuhara Tadashi , Zhang Yongjie , Miyamoto Goro 
Published: December 2019

Abstract
Alloy partitioning and segregation or precipitation at transformation interfaces have been important in designing the mechanical properties of final products. Some representative examples in high-strength low-alloy steels are briefly discussed, with an emphasis on the transformation interface. For achieving better strengthening-ductility balance in TRIP-aided low alloy steels, it is essential to control carbon enrichment in austenite during ferrite and bainite transformations and the stability of retained austenite. Recent studies on alloy partitioning including carbon enrichment into austenite, provides a deeper insight into transformation mechanisms. We show that energy dissipation during interface migration and strain energy accumulation are important factors to control carbon enrichment into untransformed austenite during the ferrite/bainite transformation. As a counterpart of TRIP steels, interphase precipitation of alloy carbides during ferrite transformation leads to high yield strength and good elongation in low-carbon ferritic steels. A key for further strengthening is clarification of the conditions for refining the carbide dispersion. It is shown that incoherent ferrite/austenite interfaces are superior nucleation sites for carbides.
Morphological characterization of bicontinuous microstructures using two-point statistics
Authors: Sun Y , Elder K L M , Voorhees P W 
Published: December 2019

Abstract
Bicontinuous structures are found in a wide range of multiphase materials. We employ the prototypical bicontinuous structure that is found following spinodal decomposition to probe the morphology and evolution of bicontinuous two-phase mixtures during coarsening using two-point statistics of the mean, total curvature, and the interfacial velocity. We find that the relative spatial variations of the interfacial velocity are larger than those of the mean curvature. In addition, interfaces with high positive and high negative values of the mean curvature, total curvature and interfacial velocity are spatially localized. Finally, the spatial distribution of interfaces with near zero interfacial velocity largely resembles that of near zero mean curvature, and have correlations only over very short distances.
Multi-dimensional characterization and controlling of microstructure evolution during solidification of metallic alloys
Authors: Wang Tongmin 
Published: December 2019

Abstract
Metallic alloys are important structural and functional materials and have been widely applied in industry. The performance of metallic alloys strongly depends on the microstructures after solidification. Many effective methods are introduced to control the microstructure evolution during solidification, including grain refining, adding rare earth (RE) elements, applying electric current and/or magnetic field, etc. However the inherent mechanisms affecting the microstructure formation are still unclear due to the limitation of real time and multidimensional characterization technique. With the development of the third generation synchrotron radiation light source, a real time imaging technology in 2D (two dimensional) or 3D (three dimensional) view with strong penetrability, high spatial and temporal resolution, nondestructive features has been developed to break those limitations. In this paper, some application cases during solidification performed in our group are reported in different alloys and using different solidification controlling techniques. Different solidification behaviors in those cases are revealed and discussed.
Sub-grain orientation resolution during continuous loading using only far-field HEDM
Authors: Nygren K E , Pagan D C , Miller M P 
Published: December 2019

Abstract
A far-field data reduction algorithm for high-energy X-ray diffraction microscopy (HEDM) has been adapted to extract sub-grain orientation descriptors in a polycrystalline material during continuous in situ loading experiments. Previously, the standard data reduction algorithm would only extract grain-averaged strains, orientation, and the centroid position. A new descriptor, the grain orientation envelope (GOE), is introduced as a measure of the intragranular microstructure extracted from every grain during a continuous loading experiment. Initial results showing the evolution of a GOE from one grain in the titanium alloy, Ti-7Al, during a tension test is presented as a demonstration of the nature of the data.
Advantages of architectured harmonic structure in structural performance
Authors: Orlov Dmytro , Zhou Jinming , Hall Stephen , Ota-Kawabata Mie , Ameyama Kei 
Published: December 2019

Abstract
The concept of heterogenous materials with architectured harmonic structure (HS) has emerged recently with the aim of enhancing the structural performance of metals. This work presents critical microstructure characteristics contributing to the superior structural performance of harmonic-structured materials using as an example of commercially-pure nickel. Optical and scanning electron microscopy, along with nano-indentation and tensile testing, as well as digital image correlation analysis, were used for this purpose. A brief overview of the structural performance of several representative systems with HS is provided and interesting directions for future studies are discussed.
Understanding structural evolution of nanostructures during deformation from 2D (3D) experiments
Authors: Renk O , Kapp M W , Pippan R 
Published: December 2019

Abstract
Understanding how microstructures evolve during deformation and/or annealing treatments is of fundamental interest, as the underlying structure dictates the resulting property spectrum. This issue is even more important for nanomaterials, where interfaces and defect populations have a stronger effect on mechanical properties. In addition, for nanometals the grain architecture can also be an important parameter for improvement of mechanical properties. However, synthesis of bulk high strength materials by severe deformation with tailored and desired properties requires a thorough understanding about the processes governing their microstructural evolution at large and severe strains. Here, we summarize findings from 2D (3D) experiments uncovering these restoration processes. Interestingly, the main mechanisms seem to change with deformation temperature, causing formation of extremely elongated grain structures at intermediate deformation temperature regimes. Apart from discussing the reasons for this finding, we also present recent results focusing on the mechanisms triggering these restoration processes at low temperatures, highlighting the crucial role of plastic strain to facilitate these processes.
Analysis of in-grain orientation distributions in deformed aluminium using X-ray diffraction and finite elements
Authors: Renversade Loïc , Quey Romain 
Published: December 2019

Abstract
The lattice orientation distributions developing inside individual grains of a polycrystalline aluminium sample subjected to plastic deformation are analysed. In the experiment, diffraction contrast tomography (DCT) and far-field 3D X-ray diffraction microscopy (3DXRD) are used to track the development of the orientation distributions of 466 grains of an aluminium polycrystal deformed in tension to successive strains of 1.0, 1.5, 2.0, 2.5 and 4.5%. A new method is presented and employed to determine the in-grain orientation distributions from broadening of the diffraction spots. The polycrystal deformation is then simulated using the crystal-plasticity finite element method, starting from the initial, DCT-determined microstructure. The experimental and numerical in-grain lattice orientation distributions are analysed and compared in terms of trends over all grains and grain by grain.
The Coupling of Grain Growth and Twinning in FCC Metals
Authors: Thomas Spencer L , Han Jian , Srolovitz David J 
Published: December 2019

Abstract
Coherent twin boundaries (CTBs) routinely form during the annealing of polycrystalline metals, in the absence of an applied stress. Molecular dynamics (MD) simulations of normal grain growth in nanocrystalline metals show such annealing twins as well the formation of twin junctions. MD simulations and theoretical analyses demonstrate how these junctions form and that their formation necessarily retards grain boundary (GB) migration. Both CTB and GB migration occurs via disconnection motion. We identify the types of disconnections important for CTB migration and show the disconnection pile-ups at TJs during GB migration are responsible for CTB formation in the vicinity of TJs. Analysis further shows that at least two types twinning partials are to be expected during TJ migration and that these give rise to the multiple twinning near migrating TJs observed in the MD simulations.
Effect of strain gradient on the microstructure and mechanical properties of pearlitic steel
Authors: Ahlström Johan , Zhang Xiaodan 
Published: December 2019

Abstract
Pearlitic steels, with a combination of good strength and wear properties, are commonly used for railway rails. The passage of trains creates large shear strain gradients in the surface layer of rails. Knowledge of the microstructural evolution and material properties as related to the shear strain in this layer is therefore important for prediction both of crack evolution and fatigue life. A bi-axial torsion-compression machine was used to deform fully pearlitic R260 rail steel test bars to create a similar gradient structure. Uniaxial tension and compression tests were performed on these pre-deformed test bars to evaluate the mechanical properties of the material. The local microstructural parameters, such as thickness of the ferrite and cementite lamellae, the dislocation density in the ferrite lamellae, the interlamellar spacing and eth local hardness at different places across the diameter of the bars, as well as microstructural evolution across the radius, were characterized. An attempt to set up a correlation between the local microstructural parameters, hardness and the macro mechanical properties is made and discussed in the present study.
Effect of heterogeneous laser surface treatment on mechanical properties of interstitial free steel
Authors: Cai Pengzhan , Lian Xiaojin , Tang Zhixiang , Zhang Ling , Wang Tingting , Chai Linjiang , Wu Guilin 
Published: December 2019

Abstract
Laser surface treatment was applied to a Ti-added interstitial-free steel by linear-scanning. The distance between each linear scan was 1.5 mm and the width of the laser-modified zone for each scan was 1 mm. These process parameters result in a heterogeneous surface, containing hard laser-modified lamella separated by non-treated material. It is found that after the treatment, higher strength and good ductility can be obtained. Electron channelling contrast imaging was used to investigate the structure of the sample, which was then compared with the untreated one to reveal the origin of the improved mechanical behaviour of the laser surface-treated steel.
In-situ study of microstructural evolution and local strain distribution during tensile loading of near-micrometre grain size aluminium
Authors: Gao W Q , Zhang C L , Zhang S Q , Godfrey A 
Published: December 2019

Abstract
A combined digital image correlation (DIC) and electron backscatter diffraction (EBSD) study of local strain distribution and microstructural evolution during tensile loading has been carried on samples of near-micrometre grain size Al prepared by spark plasma sintering. To achieve the required spatial resolution and allow combined DIC and EBSD measurements a method of surface patterning using colloidal silica was developed. The DIC results reveal a wide variety in heterogeneity of plastic strain, both in terms of the average strain experienced by each grain and regarding the extent and nature of strain localization within individual grains. No obvious correlation is found between the heterogeneity in plastic strain and either Schmid factor, grain size or the pattern of local grain rotations. The experiments also allow investigation of the pattern of crystal rotation during tension in near-micrometer grain size samples and reveal differences in the mean grain rotation and the in-grain orientation spread.
Imaging modalities at the Swedish Materials Science beamline at PETRA III
Authors: Hegedüs Z , Müller T , Hektor J , Larsson E , Bäcker T , Haas S , Conceiçao ALC , Gutschmidt S , Lienert U 
Published: December 2019

Abstract
High-energy synchrotron radiation has been demonstrated to be a powerful tool for materials characterization. The development of novel methodologies is still ongoing, driven by major technological advances regarding the available source brilliance and efficient large area detectors. The Swedish Materials Science beamline at PETRA III is dedicated to materials characterization by high-energy X-rays and scheduled to enter into user operation starting August 2019. The beamline has been designed in particular for the combination of two complementary techniques: wide and small angle scattering and imaging. The beamline design is presented briefly and the different techniques are reviewed with regard to the contrast mechanisms and the ability to obtain spatially resolved information.
Visualization of low-misorientation dislocation structures from orientation data using customized All-Euler maps
Authors: Hong Chuanshi 
Published: December 2019

Abstract
A method for visualization of low-misorientation dislocation structures from orientation data obtained by electron backscatter diffraction (EBSD) in scanning electron microscopy is presented. The method is termed “customized All-Euler maps”. The microstructure of high purity (99.996 wt.%) aluminum lightly rolled to a thickness reduction of 12% is presented as a case study. Dislocation structures with misorientations across dislocation boundaries approaching the orientation precision of standard EBSD (∼0.5°) are revealed using the customized All-Euler maps. Cautions and limitations in using such maps are discussed.
Quantification of recrystallization kinetics in industrially processed 5xxx aluminum alloy sheet
Authors: Lei X C , Sanders R E , Yang X F , Jensen D Juul 
Published: December 2019

Abstract
The annealing kinetics of two aluminum alloys AA5xxx is investigated. The volume fraction of recrystallized material, Vv, is determined for a series of partly recrystallized samples both by hardness measurements and by electron back scattering diffraction (EBSD). Because of extended recovery overlapping with recrystallization, in particular in AA5182, it is not straightforward to estimate Vv from the hardness measurements. Two methods are suggested: one relying solely on the hardness data, and one in which EBSD data are used to estimate the hardness at the onset of recrystallization. Effects of the choice of method and of parameters on the resulting annealing kinetics are analysed, and the potential and limitations of the two methods are discussed.
Microstructural evolution of Ta-4%W during cold rolling
Authors: Ma Guoqiang , Godfrey Andrew , Chen Qiang , Wu Guilin , Hughes Darcy A. , Hansen Niels 
Published: December 2019

Abstract
Tantalum alloys are regarded as materials with great potential for challenging environments due to their exceptional mechanical properties, especially at high temperatures. To analyse deformation mechanisms and the relationship between microstructure and strength, characterization of the deformation microstructure of Ta-4%W during cold rolling from 10% to 50% has been carried out by transmission electron microscopy combined with electron backscatter diffraction investigations. The microstructural evolution of Ta-4%W was found to follow the same general framework as FCC metals (Al, Cu, Ni) and IF steel, with added complexity due to the additional constraints on dislocation motion.
Heterogeneous microstructure of low-carbon lath martensite with continuous yielding behavior in Fe-C-Mn alloys
Authors: Sugiyama M , Sawa G , Hata K , Maruyama N 
Published: December 2019

Abstract
High strength steels have been rapidly developed for several kinds of application fields such as light weight automobile bodies, multistory buildings, and oil well tubulars. With an increase of strength, the use of the low-carbon lath martensite phase puts this component as the main microstructure, or a part of the dual phase one. However, the martensite is a non-equilibrium phase, and the microstructure is also a heterogeneous composite-like one including of fine carbides and retained austenite. In order to understand the hierarchical structure, multi-scale microscopic techniques have been utilized. Internal twins in a lath and some large lath domains with fine carbides are revealed by scanning electron microscope (SEM) and transmission electron microscope (TEM) observations, although a conventional low-carbon martensite is known to include mainly dislocations in the lath structure. The heterogeneous microstructure is discussed based on a model of the local difference of transformation temperature of each lath block segment during cooling. On the plasticity of low-carbon lath martensite, the continuous yielding behavior is one characteristic property, and the elastic limit is obtained by the cyclic tensile test. The heterogeneous deformation behavior is detected as a periodic strain partitioning among lath blocks in a grain by digital imaging correlation analysis using in situ SEM tensile testing.
Extraction of grain boundary curvature from voxel-based representations of polycrystalline microstructures
Authors: Wang Mingyan , Wu Shuang , Krill Carl E. 
Published: December 2019

Abstract
Extracting the curvature of grain boundaries from 3D voxel-based representations of microstructure is challenging. Previous investigations have concluded that the accuracy of curvature estimation depends strongly on the degree of smoothing after a microstructure has been meshed. We find that best results are obtained when the degree of smoothing is determined on a boundary-by-boundary basis. Evaluating a voxelized representation of a Reuleaux tetrahedron of known boundary curvature, we establish that, for a given boundary, the optimal smoothing power minimizes the coefficient of variation (CV) of local curvature. We apply the minimum-CV criterion to the extraction of grain boundary curvatures from a measurement of polycrystalline Al-5 wt% Cu performed by 3D x-ray diffraction (3DXRD) microscopy. The results show that grain boundaries in this sample are surprisingly flat. Moreover, boundaries of larger area manifest lower curvature, while higher curvature values are observed solely for boundaries of smaller area.
Simultaneous enhancement of strength and ductility in a finegrained Fe-30Mn-0.11C steel at 77 K
Authors: Wang Y H , Kang J M , Chen X M , Yu T , Hansen N , Huang X 
Published: December 2019

Abstract
High Mn austenitic steels are a class of materials for cryogenic applications. Previous studies on Fe-34.5Mn-0.04C austenitic steels have shown that refining grain size can suppress the formation of deformation-induced ε and α’ martensite and improve the tensile strength and ductility at temperatures down to 123 K. Here we report a new observation of simultaneous increase of strength and ductility at liquid nitrogen temperature (77 K) in a fine grained Fe-30Mn-0.11C (wt. %) steel where the addition of 0.11%C stabilizes the austenite. This improvement is attributed to complete suppression of martensitic transformation and enhanced occurrence of deformation twinning.
Recent progress in dilatometry for quantitative analysis of precipitation kinetics
Authors: Würschum Roland , Enzinger Robert , Hengge Elisabeth , Sprengel Wolfgang 
Published: December 2019

Abstract
A high-stability non-contact dilatometer based on two-beam Michelson interferomtry was developed recently, enabling isothermal measurements of relative length changes in the sub-10−5 regime with minimized drift over times as long as 106 s. This advanced technique opens up novel potentials for quantitative studies of precipitation phenomena, which are associated with tiny relative length changes that have not been accessible before. Using a dilute Al-Mg- Si alloy as a case study, the amount of the metastable coherent β″- and of the semi-coherent β’-phase, as well as the amount of the stable β-phase could be determined quantitatively from isothermal length change measurements. This is accomplished by the distinct length change features that arise from the volume excess due to the precipitates, on the one hand, and the contraction of the matrix upon precipitation of solute atoms, on the other hand. Moreover, reaction-rate analyses of isothermal length change variations yield the kinetic parameters for the formation and transformation of the precipitates.
Deformation microstructures and strength of face-centered cubic high/medium entropy alloys
Authors: Yoshida Shuhei , Ikeuchi Takuto , Bai Yu , Shibata Akinobu , Hansen Niels , Huang Xiaoxu , Tsuji Nobuhiro 
Published: December 2019

Abstract
In this study we report the deformation microstructures and strength of medium entropy alloys (MEAs) and high entropy alloys (HEAs), which are defined as alloys composed of four or less, and five or more principal elements, respectively, with (near-) equi-atomic concentrations. The friction stress (fundamental resistance to dislocation motion in the crystal lattice) and Hall-Petch relationship of various MEAs (CoCrFeNi, CoCrNi, etc.), taken as subsystems of the equi-atomic CoCrFeMnNi HEA, were precisely measured at room temperature. Experimental values of the friction stresses were found to fit with a theoretical model proposed by Toda-Caraballo et al. very well, which indicates that the strength of the alloys is closely related to a heterogeneously distorted crystal lattice. At the same time, values of the average lattice distortion in the alloys were found to be comparable to those in some dilute alloys, contradicting the belief that “severe” lattice distortion is a reason for the higher strength than in dilute systems. Finally, a strengthening mechanism due to element-element interactions was proposed as an additional mechanism in FCC HEAs and MEAs.