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  • In situ, 3D characterization of the deformation mechanics of a superelastic NiTi shape memory alloy single crystal under multiscale constraint
    Acta Mater. (IF 5.301) Pub Date : 2017-11-20
    Harshad M. Paranjape, Partha P. Paul, Behnam Amin-Ahmadi, Hemant Sharma, Darren Dale, J.Y. Peter Ko, Yury I. Chumlyakov, L. Catherine Brinson, Aaron P. Stebner

    Microstructural elements in NiTi shape memory alloys (SMAs) – precipitates, phase boundaries, inclusions, grain boundaries – can be viewed as sources of multiscale constraint that influence their deformation response. We characterized in situ, and in 3D, the deformation and the evolution of microstructure during a tension test in a superelastic NiTi specimen containing some of these sources of constraint. The method used was far-field high-energy X-ray diffraction microscopy (ff-HEDM), complemented by electron microscopy. We simulated the local stress state in the specimen using a microstructural model informed by the experimental data. Using these combined microstructure, deformation, and stress data, we report three phenomena, and relate them to specific sources of constraint. During initial elastic loading, axial lattice strain in austenite increased monotonically. On partial stress-induced phase transformation to martensite, the stress redistributed to both phases leading to a stress relaxation in austenite. The specimen contained a dense distribution of inclusions, which led to the activation of martensite habit plane variants that produce less than theoretical maximum transformation strain. Large Ni4Ti3 precipitates potentially contributed to the poor transformation response. Under load, proportional gradients in local rotation and elastic stretch developed in the martensite phase, because of the constraint at phase interfaces. This combined ff-HEDM, electron microscopy, microstructural simulation toolbox provides a versatile method to understand the effect of constraint on inelastic deformation in other alloys with hierarchical microstructure.

    更新日期:2017-11-21
  • Analysis of thermal desorption of hydrogen in metallic alloys
    Acta Mater. (IF 5.301) Pub Date : 2017-11-20
    A. Raina, V.S. Deshpande, N.A. Fleck

    The degree of embrittlement of metallic alloys is sensitive to the concentration of absorbed hydrogen, with hydrogen traps (particularly at grain boundaries) playing an important role. Thermal desorption spectrometry (TDS) is widely used to measure the detrapping and diffusion behaviour of hydrogen in metallic alloys. However, it is problematic to obtain a consistent interpretation of TDS data from the literature, due to the large number of material parameters that influence the measurement, and this results in a wide range of quoted values for trapping parameters such as the number of trap types, trap binding energies and trap densities. In this paper, the governing partial differential equation for hydrogen diffusion with sink and source terms for a single trap is formulated in non-dimensional form, assuming local equilibrium between the hydrogen atoms at the lattice sites and the trap sites. An asymptotic analysis reveals two distinct regimes of diffusion behaviour in TDS tests. Kissinger-type behaviour is expected in a TDS test for low heating rates on an alloy with a low lattice activation energy. Contour maps of maximum hydrogen flux and the corresponding temperature are plotted using axes of trap density and trap binding energy by making use of the full numerical solution (and asymptotic solutions). These maps serve as a useful tool for an accurate and simple determination of the trap binding energy as well as the trap density.

    更新日期:2017-11-21
  • Elucidating the effect of Mn partitioning on interface migration and carbon partitioning during Quenching and Partitioning of the Fe-C-Mn-Si steels: Modeling and experiments
    Acta Mater. (IF 5.301) Pub Date : 2017-11-17
    Zongbiao Dai, Ran Ding, Zhigang Yang, Chi Zhang, Hao Chen

    A fundamental understanding of carbon partitioning and the martensite/austenite interface migration during the Quenching & Partitioning (Q&P) process is essential for tailoring the microstructures of the advanced Q&P steels. In this study, two Q&P models (QP-LE and QP-PE), in which effects of substitutional alloying elements have been considered by assuming Local Equilibrium (LE) or Paraequilibrium (PE) at the interface, are proposed to simulate the kinetics of martensite/austenite interface migration and carbon partitioning in the Fe-C-Mn-Si steels. The QP-LE and QP-PE models predict that whether the interface migrates or not and its moving direction are dependent on quenching/partitioning temperature (QT/PT) and alloy composition. A careful comparison between experiments and model predictions indicates that the dependence of interface migration behavior on QT/PT indirectly measured by experiments during the Q&P process could be explained reasonably well by the QP-LE model, rather than the Constrain Carbon Equilibrium (CCE) model and the QP-PE model. The carbon partitioning behavior is also well predicted by the QP-LE model while the QP-PE model predictions deviate significantly from experiments. The current study suggests that interfacial partitioning of Mn plays a significant role in carbon partitioning and interface migration during the Q&P process.

    更新日期:2017-11-17
  • Tensile properties and deformation mode of Si-added Fe-18Mn-0.6C steels
    Acta Mater. (IF 5.301) Pub Date : 2017-11-17
    Sang-Min Lee, Seung-Joon Lee, Sukjin Lee, Jae-Hoon Nam, Young-Kook Lee

    The effects of Si concentration and austenite grain size (AGS) on the tensile properties, stacking fault energy (γ), and deformation mode of Fe-18Mn-0.6C (wt.%) steel were investigated to improve the yield strength (YS) of twinning-induced plasticity (TWIP) steel. The 3% Si-added steel revealed the higher YS than previous TWIP steels at the same level of AGS. In particular when the AGS was ∼6.8 μm, its YS reached ∼593 MPa, which is comparable to the YS (613 MPa) of transformation-induced plasticity steel with a tensile strength of 980 MPa. The measured γ of 3% Si-added steel was exponentially decreased with grain coarsening primarily due to the reduction of micro-strain, finally reaching its intrinsic γ (γint) at the AGSs above ∼70 μm. This indicates that the γint measurement by means of X-ray diffractometry must be performed using coarse-grained specimens with the AGSs above ∼70 μm. Critical resolved shear stresses for twinning (τtwin) and ε-martensitic transformation (τε-mart) were evaluated as a function of AGS in (0-3%) Si-added steels. Whereas the τtwin value was slightly decreased with increasing AGS or Si concentration, the τε-mart value was more significantly reduced. This indicates that ε-martensitic transformation precedes mechanical twinning with increasing AGS or Si concentration. As a result, a transition of deformation mode from mechanical twinning to ε-martensitic transformation occurred with grain coarsening in Si-added steels. A critical AGS for the transition of deformation mode was reduced from ∼69 μm to ∼15 μm with increasing Si concentration from 0.5 wt.% to 3.0 wt.%.

    更新日期:2017-11-17
  • Brittle crack propagation resistance inside grain and at high angle grain boundary in 3% Si-Fe alloy
    Acta Mater. (IF 5.301) Pub Date : 2017-11-16
    Daiki Nakanishi, Tomoya Kawabata, Shuji Aihara

    Brittle fracture in carbon steel has a strong impact on the safety of the structures. Especially, the arresting technology of the running crack is the measure of last resort for ensuring structural integrity. Due to such high importance, many experimental and theoretical studies of brittle crack propagation have been conducted from both mechanical and microstructural viewpoints. It is thought that the elementary step of the brittle fracture of polycrystalline steel is the cleavage in each crystal grain and their connection process. However, the detailed mechanisms of brittle fracture have not been fully understood; for example, it is still unclear why the propagation rate under a large driving force is not increased up to the Rayleigh wave speed. Several difficulties hinder the achievement of a detailed understanding so far: 1) crack propagation is quite rapid, 2) the crystal grain is usually too small (10-100 μm) to collect sufficient information, 3) the microstructure is very complicated in most case, i.e., containing different phases, microstructures, precipitates and inclusions. In this study, to eliminate such difficulties, 3% silicon steel in which microstructure is the ferrite single phase and the grain size is increased to 4-5mm is used. This steel can be fractured in a brittle manner, even under ambient temperature. For this steel, by using a high speed camera and strain gauge data with a high sampling rate, the elementary process of brittle crack propagation is elucidated. As a result, it is revealed that the brittle crack propagation rate even in a single-crystal grain is much slower than the Rayleigh wave speed. This seems to be due to the presence of twin deformations and twin boundary cracks in crystal grain as observed on the fracture surface. Using the analysis of electron back scatter diffraction (EBSD) data, the mechanism of twin deformation and twin boundary crack is revealed. Additionally, it is shown that the brittle crack propagation rate where the path includes crystal grain boundaries is much slower. This delay seems to be related to the misorientation angle at the GB. By applying our simplified model, the delay effect at the grain boundary can be successfully explained.

    更新日期:2017-11-16
  • Application of Spherical Indentation and the Materials Knowledge System Framework to Establishing Microstructure-Yield Strength Linkages from Carbon Steel Scoops Excised from High-Temperature Exposed Components
    Acta Mater. (IF 5.301) Pub Date : 2017-11-15
    Almambet Iskakov, Yuksel C. Yabansu, Sudhir Rajagopalan, Anna Kapustina, Surya R. Kalidindi

    Industrial power generation turbines operate at elevated temperatures for prolonged periods of time (around 100,000 hours) which leads to significant microstructure evolution and mechanical property changes. Due to physical and structural constraints of operational turbines, only small scoop samples can be excised from heat-exposed steel components. Scoop samples at various service time intervals provide valuable information on microstructure changes, for example on graphite formation in carbon steels, with increasing service time. However, mechanical evaluation of such small material volumes poses significant challenges using conventional tests. A novel spherical microindentation technique is applied to evaluate a library of scoop samples ranging between 0-99,000 hours of service. Furthermore, microstructure and yield strength data for the different exposure periods is used to construct a structure-property (S-P) linkage using the MKS homogenization approach that employs spatial correlations, principal component analysis, and regression techniques. The accuracy of the extracted S-P linkage was assessed on new samples that were not included in the calibration set.

    更新日期:2017-11-16
  • Effects of Laves phase particles on recovery and recrystallization behaviors of Nb-containing FeCrAl alloys
    Acta Mater. (IF 5.301) Pub Date : 2017-11-15
    Zhiqian Sun, Philip D. Edmondson, Yukinori Yamamoto

    The microstructures and mechanical properties of deformed and annealed Nb-containing FeCrAl alloys were investigated. Fine dispersion of Fe2Nb-type Laves phase particles was observed in the bcc-Fe matrix after applying a thermomechanical treatment, especially along grain/subgrain boundaries, which effectively stabilized the recovered and recrystallized microstructures compared with the Nb-free FeCrAl alloy. The stability of recovered areas increased with Nb content up to 1 wt%. The recrystallized grain structure in Nb-containing FeCrAl alloys consisted of elongated grains along the rolling direction with a weak texture when annealed below 1100 °C. An abnormal relationship between recrystallized grain size and annealing temperature was found. Microstructural inhomogeneity in the deformed and annealed states was explained based on the Taylor factor. Annealed Nb-containing FeCrAl alloys showed a good combination of strength and ductility, which is desirable for their application as fuel cladding in light-water reactors.

    更新日期:2017-11-16
  • Atomistic investigation into the mechanical properties of the ferrite-cementite interface: The Bagaryatskii orientation
    Acta Mater. (IF 5.301) Pub Date : 2017-11-15
    Matthew Guziewski, Shawn P. Coleman, Christopher R. Weinberger

    Atomistic modeling is used to investigate the mechanical response to compressive and tensile straining of the Bagaryatskii orientation relationship between ferrite and cementite within pearlite. A range of interlamellar spacings and ferrite to cementite ratios are considered and values for important mechanical properties, including elastic modulus, yield stress, flow stress, and ductility, are determined. These values are fit to simple elasto-plastic models, thus allowing for the easy interpolation of states not simulated. Transverse loading can be described using simple 1-D composite theory, while longitudinal loading requires the consideration of the strain compatibility of the interface. The mechanical properties are shown to be largely dependent on the volume ratios of the cementite and ferrite, with the interlamellar spacing having an increasing role as it reaches smaller values. Additionally, the effect of the interface is discussed and characterized, including its role as a nucleation site for dislocations in both the ferrite and cementite.

    更新日期:2017-11-16
  • Mimicking tetravalent dopant behavior using paired charge compensating dopants to improve the redox performance of ceria for thermochemically splitting H2O and CO2
    Acta Mater. (IF 5.301) Pub Date : 2017-11-15
    Christopher Muhich, Marie Hoes, Aldo Steinfeld

    A novel doping strategy based on paired charge compensating dopants is proposed to improve the solar thermochemical H2O and CO2 splitting performance of ceria. Density functional theory based ab initio calculations show that by co-doping trivalent and pentavalent cations into ceria the behavior of the trivalent dopant resembles that of tetravalent dopants. In this study, which investigated combinations of group IIIA and VA elements, it was found that the trivalent dopant identity has the largest effect on the reduction energy, while the pentavalent dopant only slightly modifies it. The trivalent dopant in these materials suppresses the reduction energy due to decreased ionic attraction of the trivalent cation and O2− as compared to Ce4+ and O2−. We predict relative reducing capabilities in the following decreasing order: Hf-CeO2 > ScX-CeO2 > Zr-CeO2 > YX-CeO2 > LaX-CeO2 > undoped CeO2 (where X = V, Nb or Ta). Experimental thermogravimetric analysis confirms the computational predictions.

    更新日期:2017-11-15
  • Study of point defects diffusion in nickel using kinetic activation-relaxation technique
    Acta Mater. (IF 5.301) Pub Date : 2017-11-14
    Sami Mahmoud, Mickaël Trochet, Oscar A. Restrepo, Normand Mousseau

    Point defects play a central role in materials properties. Yet, details regarding their diffusion and aggregation are still largely lacking beyond the monomer and dimer. Using the kinetic Activation Relaxation Technique (k-ART), a recently proposed off-lattice kinetic Monte Carlo method, the energy landscape, kinetics and diffusion mechanisms of point defect in fcc nickel are characterized, providing an exhaustive picture of the motion of one to five vacancies and self-interstitials in this system. Starting with a comparison of the prediction of four empirical potentials — the embedded atom method (EAM), the original modified embedded atom method (MEAM1NN), the second nearest neighbor modified embedded atom method (MEAM2NN) and the Reactive Force Field (ReaxFF) —, it is shown that while both EAM and ReaxFF capture the right physics, EAM provides the overall best agreement with ab initio and molecular dynamics simulations and available experiments both for vacancies and interstitial defect energetics and kinetics. Extensive k-ART simulations using this potential provide complete details the energy landscape associated with these defects, demonstrated a complex set of mechanisms available to both vacancies and self-interstitials even in a simple environment such as crystalline Ni. We find, in particular, that the diffusion barriers of both vacancies and interstitials do not change monotonically with the cluster size and that some clusters of vacancies diffuse more easily than single ones. As self-interstitial clusters grow, moreover, we show that the fast diffusion takes places from excited states but ground states can act as pinning centers, contrary to what could be expected.

    更新日期:2017-11-15
  • Non-equilibrium solid solution of molybdenum and sodium: Atomic scale experimental and first principles studies
    Acta Mater. (IF 5.301) Pub Date : 2017-11-13
    Beate Bergk, Uwe Mühle, Ivan Povstugar, Nikola Koutná, David Holec, Helmut, Clemens, Bernd Kieback

    We report a combined experimental and first principles study of an extremely immiscible alloy of Mo with 1 and 2 at.% Na, which was produced by high-energy ball milling. The microstructure of the as-milled and annealed state were examined by various methods, including atom-probe tomography (APT), transmission electron microscopy, and energy-dispersive (EDX) analysis. Despite the complete immiscibility of the Mo-Na system in the solid and even in the liquid state, APT measurements clearly evidence the formation of a true nanocrystalline solid-solution microstructure with insignificant Na clustering for samples with 1 at.% Na. In agreement with our x-ray diffraction experiments, first principles calculations expose that the Na atoms do not expand the Mo lattice, which is in contrast to predictions using Vegard’s rule. Heating at 700°C induces only slight grain growth while the solid solution remains remarkably stable without any decomposition. On the contrary, after annealing at 900°C first Na segregations at triple junctions and significant grain growth are observable, although the solid solution still retains most of the dissolved Na.

    更新日期:2017-11-14
  • Atom probe tomography study of Fe-Ni-Al-Cr-Ti ferritic steels with hierarchically-structured precipitates
    Acta Mater. (IF 5.301) Pub Date : 2017-11-13
    Sung-Il Baik, Michael J.S. Rawlings, David C. Dunand

    The ferritic Fe-Ni-Al-Cr-Mo steel (FBB8) has good creep properties up to 700 °C due to B2-NiAl nanoscale precipitates and its creep resistance can be further improved by additions of 2 or 4% Ti, as a result of sub-precipitates within the main precipitates. Here, the hierarchical structure of the precipitates is studied in the light of phase separation via transmission electron microscopy (TEM) and atom probe tomography (APT). For FBB8-2Ti (with 2% Ti added) exhibiting B2-NiAl precipitates with L21-Ni2AlTi sub-precipitates, APT analysis shows strong partitioning of Ni, Al and Ti from the ferritic matrix into the B2/L21 precipitates and, within the precipitates, partitioning of Ti and Fe within the L21 sub-precipitates. Based on the published pseudo-binary phase-diagram between (Ni,Fe)Al and (Ni,Fe)Ti, this hierarchical precipitate microstructure is discussed based on the known miscibility gap between the B2 and L21 phases, due to partitioning of Ti into the L21 phase and ordering of Al and Ti on the Al sub-lattice of the B2 structure. For FBB8-4Ti (with 4% Ti added), by contrast, the L21 precipitates exhibit bcc sub-precipitates rich in Fe and Cr, with a composition close to that of the matrix; the absence of the B2 structure is consistent with an increase of Fe concentration, to 19.3 at.%, as measured via APT, in the L21 precipitates.

    更新日期:2017-11-13
  • Crystal structure of Th2B2C3 with unique mixed B-C structural units
    Acta Mater. (IF 5.301) Pub Date : 2017-11-12
    P.F. Rogl, R. Podloucky, H. Noël, G. Giester

    X-ray single crystal data for "ThBC2" defined the crystal structure as orthorhombic (space group Pnnm; a=1.30655(3) nm, b=0.39757(1) nm, c=0.36507(1) nm; RF2=0.0130) with the correct formula Th2B2C3. According to the new findings phase relations for the Th-B-C system at 1400°C have been revised confirming the hitherto known thorium-boron-carbon compounds: ThBC, ThB2C and Th3B2C3. The crystal structure of Th2B2C3 as a unique structure type is characterized by a C2-branched infinite chain ...B-C1-B-B-C1-B... whereby each boron atom is additionally linked to a C2-atom. Boron atoms are in a typical triangular prismatic metal coordination, C1-atoms center a bi-pyramid, Th4B2, and C2-atoms are surrounded by 5 pyramidal Th-atoms and one B-atom. Density functional theory calculations were made within the pseudopotential approach of VASP utilizing the general gradient approximation for the exchange correlation functional. Structural parameters were optimized resulting in the orthorhombic lattice parameters of a=1.3144 nm, b=0.3989 nm, and c=0.3656 nm. Relativistic calculations by including spin-orbit coupling were performed for the electronic structure. Atomic volumes and charges were computed by the concept of Bader yielding the ionic charges Δq(Th)=+0.99; Δq(B)=+0.61; Δq(C1)=-1.20; Δq(C2)=-1.10. The analysis of the electronic structure shows features of chains and corresponding structural subunits with σ-like bonding. The compound appears weakly metallic with a Sommerfeld constant of γ = 3.12 mJ/(molK2) per formula unit.

    更新日期:2017-11-13
  • Exploring the fatigue strength improvement of Cu-Al alloys
    Acta Mater. (IF 5.301) Pub Date : 2017-11-11
    R. Liu, Y.Z. Tian, Z.J. Zhang, P. Zhang, X.H. An, Z.F. Zhang

    As a significant scientific problem directly impacting on the long-term safety of engineering materials and facilities, the improvement of fatigue strength under fully-reversed cycling was comprehensively explored in this study. Advantageous material characteristics for the improvement of fatigue strength were summarized from the achievements of the previous researches, followed by a new attempt to combine them in material design. As the model material, α-Cu-Al alloys with clean ultrafine-grains as well as large proportions of twin boundaries were thus produced, which exhibited a notable fatigue strength improvement (up to 155 % higher than the coarse-grained counterparts and 40 % higher than the counterparts produced by severe plastic deformation). Furthermore, a general principle briefly summarized as localized fatigue damage reduction was proposed based on the analysis of the optimizing methods including microstructure optimization and composition optimization. Accordingly, several recommended features to obtain such high fatigue strength materials were finally listed for further anti-fatigue design, such as uniform grains with small size and stable boundaries; low initial dislocation density, and proper alloying composition.

    更新日期:2017-11-13
  • Orientation of austenite reverted from martensite in Fe-2Mn-1.5Si-0.3C alloy
    Acta Mater. (IF 5.301) Pub Date : 2017-11-10
    Xianguang Zhang, Goro Miyamoto, Yuki Toji, Shoichi Nambu, Toshihiko Koseki, Tadashi Furuhara

    The orientation of austenite (γ) reverted from lath martensite has been studied using electron backscatter diffraction (EBSD) in Fe-2%Mn-1.5%Si-0.3%C (mass%) alloy. Two morphologies of γ, acicular and globular, are formed during reversion. Nucleation sites for acicular γ are lath, block and sub-block boundaries, while those for globular γ are prior γ grain boundaries, as well as inside packets. Both acicular and globular γ hold a near Kurdjumov-Sachs (K-S) orientation relationship with at least one of its surrounding tempered martensite blocks. Most acicular γ have almost identical orientations with the prior γ, while only a part of acicular γ have a specific twin-related variant with the prior γ. Furthermore, grain boundary globular γ has almost identical orientations with the prior γ into which it does not grow. The formation of acicular and grain-boundary globular γ was attributed to strong variant selection during γ nucleation at lath, block and sub-block boundaries. On the other hand, orientation relationship analyses among intragranular globular γ, tempered martensite and cementite suggest that the nucleation of γ at cementite and tempered martensite interfaces causes weakening of the variant selection for the formation of intragranular globular γ.

    更新日期:2017-11-11
  • Wetting and solidification of silver alloys in the presence of tungsten carbide
    Acta Mater. (IF 5.301) Pub Date : 2017-11-09
    Nachiketa Ray, Ludo Froyen, Kim Vanmeensel, Jef Vleugels

    The wettability of pure Ag and Ag alloys (with Ni and Cu) on WC was investigated as a function of temperature by means of sessile drop experiments. Ni was found to preferentially segregate at the Ag/WC interface resulting in a decreased contact angle as compared to Cu. The influence of the Ni content and WC particle size on the solidification behavior of Ag in infiltrated Ag-WC-Ni (40 wt% WC and 0.07/5 wt% Ni) composites was assessed, revealing the pushing of WC particles by the solidification front, especially in the materials with a finer WC particle size. Addition of Ni decreased the grain size of the Ag phase by promoting heterogeneous nucleation. Complete coherency between the Ag and Ni phases was confirmed by electron backscattered diffraction analysis.

    更新日期:2017-11-10
  • Sintering behaviors of micron-sized ceramic rod features
    Acta Mater. (IF 5.301) Pub Date : 2017-11-08
    Hong-fei Ju, Kaijie Ning, Kathy Lu

    When ceramic features decrease to much smaller sizes, such as in the micron range, the dominating sintering mechanism(s) can be different from those of the bulk at large scales. In this work, the sintering behaviors of ZnO rod features of ∼4 μm diameter are studied. The rods and the bulk of the ZnO ceramics have different behaviors in shrinkage, grain growth, and densification. Sintering mechanisms are mainly grain boundary diffusion controlled densification and pore gas diffusion controlled grain growth, but with the major difference associated with a factor Ng/Nb (Ng, average pore number per grain; Nb, average pore number per grain boundary) based on the theoretical modeling and Voronoi diagram simulation. The smaller Ng/Nb for the micron-sized features leads to enhanced grain growth, and the higher exposed surface area leads to larger shrinkage; both can be explained using nominal Dgs/Dgb. Nanoparticle agglomeration can potentially affect grain growth in the rods during sintering and should be further studied.

    更新日期:2017-11-10
  • Enhanced radiation tolerance of YSZ/Al2O3 multilayered nanofilms with pre-existing nanovoids
    Acta Mater. (IF 5.301) Pub Date : 2017-11-08
    Hui Wang, Feng Ren, Jun Tang, Wenjing Qin, Lulu Hu, Lan Dong, Bin Yang, Guangxu Cai, Changzhong Jiang

    Utilization of high density small sinks, such as voids, to collect and store helium atoms inside might be a potential new strategy for designing nanostructured materials with high radiation resistance to swelling and embrittlement. To understand the role of pre-existing nanovoids on irradiation, we investigated the evolutions of micro-structure and mechanical properties of the YSZ/Al2O3 multilayered nanofilms irradiated by He+ ions to different fluences. Compared to the Al2O3 monolithic film and the single crystal bulk YSZ, smaller He bubbles were found in the Al2O3 layers of the YSZ/Al2O3 multilayered nanofilms with pre-existing nanovoids after He+ ion irradiation. The growth of He bubbles was restricted inside the Al2O3 layers to avoid the formation of large bubbles. In contrast to the radiation-induced hardening in traditional materials, radiation-induced softening is observed in the YSZ/Al2O3 multilayered nanofilms with pre-existing nanovoids irradiated to high fluences. In addition, the Hardness to Young's modulus (H/E) ratio of the YSZ/Al2O3 multilayered nanofilms increases in response to irradiation, which suggests a potential improvement in the wear resistance of the irradiated YSZ/Al2O3 multilayered nanofilms. A defect “loading-unloading” effect at the interfaces was proposed to explain the enhanced radiation tolerance.

    更新日期:2017-11-10
  • High-resolution electron microscopy characterization of modulated structure in high Nb-containing lamellar γ-TiAl alloy
    Acta Mater. (IF 5.301) Pub Date : 2017-11-08
    Guo-dong Ren, Jian Sun

    The microstructure in a lamellar γ-based Ti-45Al-8.5Nb alloy has been investigated by transmission electron microscopy (TEM). The results show that there exists a nano-scale modulated structure with tweed contrast within α2 laths and the orthorhombic phase as a constituent of the modulated structure has the O1 structure with a random occupancy of Ti and Nb atoms on the Wyckoff sites 8g and 4c2. The orthorhombic phase has a thin plate-like morphology with orientation relationships of {001}O//{0001}α2 and <110>O//<11<img height="16" border="0" style="vertical-align:bottom" width="10" alt="Full-size image (<1 K)" title="Full-size image (<1 K)" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S135964541730959X-egi104WGQ2V7KD.jpg">0>α2. The habit plane for orthorhombic phase variants lies at {350}O//{13<img height="16" border="0" style="vertical-align:bottom" width="10" alt="Full-size image (<1 K)" title="Full-size image (<1 K)" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S135964541730959X-egi10TQJGJQBFT.jpg">0}α2, and the O1/α2 interface is not atomic flat. The results further exhibit an enrichment of Nb in the orthorhombic phase in comparison with the α2 parent phase. Based on the TEM evidences, the formation of the orthorhombic phase arises from a phase separation reaction in the α2 parent phase, which is dominated by a diffusion mechanism.

    更新日期:2017-11-10
  • Effect of electric current on densification behavior of conductive ceramic powders consolidated by spark plasma sintering
    Acta Mater. (IF 5.301) Pub Date : 2017-11-07
    Geuntak Lee, Eugene A. Olevsky, Charles Manière, Andrey Maximenko, Oleg Izhvanov, Christina Back, Joanna McKittrick

    The densification mechanism of conductive powders is revealed by comparing the electric current-assisted spark plasma sintering (SPS) of ZrN powder with conventional hot pressing (HP) carried out with the same powder and under the same pressure and temperature. To determine the actual temperature inside ZrN powder, a sacrificial thermocouple is directly inserted into the powder during the SPS process. The spatial distribution of the electric current passing through the powder is calculated using the finite element modeling. The porosity-interparticle neck area geometrical relationship is applied to estimate the electric current density inside the powder volume subjected to SPS. For the first time, by taking into account the explicit influence of the electric current effect on the SPS densification mechanism, the constitutive equations describing the electric current-assisted hot pressing of powders are developed. The densification mechanism of ZrN is determined by the inverse regression of the new SPS constitutive equations and by utilizing the experimental results on ZrN powder consolidation with and without the participation of the electric current effect.

    更新日期:2017-11-10
  • Microstructural evolution and deformation behavior of Al-Cu alloys: A transmission X-ray microscopy (TXM) and micropillar compression study
    Acta Mater. (IF 5.301) Pub Date : 2017-11-07
    C. Shashank Kaira, Christopher Kantzos, Jason J. Williams, Vincent De Andrade, Francesco De Carlo, Nikhilesh Chawla

    A unique approach to correlating an evolving 3D microstructure in an Al-Cu alloy and its micro-scale mechanical properties has been introduced. Using these nanoscale three-dimensional microstructures derived from Transmission X-ray Microscopy (TXM), individual contributions from different strengthening mechanisms were quantified. The spatial distribution and morphology of the individual θʹ and θ phases were seen to play an important role in influencing dislocation storage. Uniaxial micro-compression experiments were used to quantify the stress-strain response of the alloy at different aging times. Transmission electron microscopy (TEM) aided in discerning dislocation activity at these precipitates. A model is proposed to accurately predict the variation in yield stress by using appropriate morphological parameters from the 3D microstructure and its validity has been corroborated using experimental measurements. Distributions of 2D and 3D inter-precipitate spacing were seen to provide crucial insights on influencing deformation in such precipitation-strengthened alloys. Finally, the transition in deformation behavior and origin of numerous strain bursts were investigated using in situ micropillar compression testing.

    更新日期:2017-11-10
  • Interplay between thermodynamic and kinetic stabilization mechanisms in nanocrystalline Fe-Mg alloys
    Acta Mater. (IF 5.301) Pub Date : 2017-11-07
    Dor Amram, Christopher A. Schuh

    Mechanisms governing thermal stability of nanocrystalline metal alloys have typically been classified as either “kinetic” or “thermodynamic”, although both should generally be expected to manifest at the same time and either act constructively, or compete. The aim of this work is to present a quantitative study of thermal stability in ball-milled Fe-Mg alloys with two concurrent stabilization mechanisms at play—grain boundary segregation and Zener pinning by oxide nanoparticles—to assess their relative potency and to explore the interplay between them. To that end, we studied the alloys' configuration and attendant thermal stability by varying their composition, annealing time, temperature and atmosphere. At the mesoscale, both grain growth and oxide evolution were tracked by in-situ annealing during x-ray diffraction, as well as by electron microscopy and atom probe tomography. At the nanoscale, the local grain boundary chemistry was also probed. We discuss our results, which lie between the expectations from each separate mechanism, in terms of two primary interactions them. These results also suggest a method to control both grain and oxide precipitate size within a unified framework, and thus helps elaborate the design space for nanocrystalline alloys.

    更新日期:2017-11-10
  • Point defects at the Σ5(012)[100] grain boundary in TiN and the early stages of Cu diffusion: An ab initio study
    Acta Mater. (IF 5.301) Pub Date : 2017-11-06
    Maxim N. Popov, Anton S. Bochkarev, Vsevolod I. Razumovskiy, Peter Puschnig, Jürgen Spitaler

    Diffusion of impurities along grain boundaries of compound materials is of high relevance for multiple practical applications. In this work, we perform a case study of Cu-impurity diffusion along the special coincident site lattice model Σ5Σ5(012)[100] GB in stoichiometric and off-stoichiometric TiN. The study includes a thorough investigation of the GB structure, formation of point defects and their interaction with a Cu-impurity at the interface as well as the evaluation of energy barriers for a few plausible impurity migration pathways along TiN grain boundaries. The results show that one of the most probable diffusion mechanisms (with an activation energy of 0.77 eV) is Cu-interstitial migration along a grain boundary channel. For a non-stoichiometric case when nitrogen vacancies can be present at GB, the results show that they can act as trapping centers for Cu atoms and increase the migration energy barrier to 1.2 eV. However, our results also indicate that at equilibrium conditions the effect of trapping may be reduced due to slightly unfavored segregation of N vacancies at TiN grain boundaries.

    更新日期:2017-11-10
  • Formation mechanism of stable NbC carbide phase in Nb-1Zr-0.1C (wt.%) alloy
    Acta Mater. (IF 5.301) Pub Date : 2017-11-05
    B. Vishwanadh, A. Arya, R. Tewari, G.K. Dey

    In the present work, several long standing issues related to the formation of various carbides and transformation of Nb2C→NbC carbide in Nb-1Zr-0.1C alloy have been addressed. For this purpose, samples were processed by two routes. In the first route, as-solidified samples were extruded and recrystallized and in the second route, as-solidified samples were directly heat treated without imparting deformation. By combining detailed diffraction analyses and ab-initio calculations, identity of the Nb2C carbides in the as-solidified and extruded samples, among the various reported Nb2C crystal structures has been established as an orthorhombic crystal structure (α-Nb2C) having Pnma space group. Chemical analyses showed that the Nb2C carbides in extruded samples had higher Zr content as compared to the carbides formed in as-solidified samples. Experimental and theoretical results revealed that Zr destabilizes Nb2C phase which was shown as a possible reason for the precipitation of a more stable (Nb,Zr)C phase in recrystallized as well as in directly heat treated as-solidified samples. Detailed precession electron diffraction analysis of (Nb,Zr)C particles showed that if the nucleation of precipitates occurs prior to recrystallization and the growth of the precipitates occurs simultaneously with recrystallization, precipitates do not exhibit specific orientation relationship (OR) with the matrix phase. In contrast, if nucleation and growth of precipitates take place after recrystallization or in samples which do not undergo recrystallization, a specific (Baker-Nutting) OR is followed. Finally, by establishing atomic interrelationship by high resolution electron microscopy, the formation mechanisms of (Nb,Zr)C carbides in different morphologies in Nb alloy have been explained.

    更新日期:2017-11-10
  • Indentation size effect in unirradiated and ion-irradiated 800H steel at high temperatures
    Acta Mater. (IF 5.301) Pub Date : 2017-11-04
    A. Prasitthipayong, S.J. Vachhani, S.J. Tumey, A.M. Minor, P. Hosemann

    Nanoindentation is a widespread and useful method for evaluating mechanical properties at the sub-micron length scale. However, the indentation size effect remains a major obstacle to obtain meaningful macroscopic mechanical properties from small volume testing. This work systematically addresses the Indentation Size Effect (ISE) phenomenon as a function of temperature and defect density in an austenitic Fe-Cr-Ni alloy (800H) to establish the baseline for nanoindentation testing of ion-irradiated alloys in environmental conditions. The 800H steel sample was irradiated with 70 MeV Fe9+ at 450 °C to the total dose of 20.68 dpa. All samples were tested up to 300 °C in order to quantify the effect of temperature on the indentation size effect. It was found that in all cases, the ISE is less pronounced at high temperatures due to the increase of the plastic zone. For the same grain orientation, the indentation size effect is less pronounced in the irradiated 800H at all temperatures.

    更新日期:2017-11-10
  • Substitution behavior of Si atoms in the Ti2AlC ceramics
    Acta Mater. (IF 5.301) Pub Date : 2017-11-04
    Chengjie Lu, Kseniia Piven, Qin Qi, Jie Zhang, Gilles Hug, Aurelie Jankowiak

    The substitution of Si atoms in the Ti2AlC ceramics has been observed in the Ti2AlC brazing joints using AlSi eutectic filler alloy, contributing to the formation of Ti2(Al, Si)C solid solution in the interaction area according to the SEM analysis. Afterwards, a detailed characterization was performed using FIB/TEM technique. A remarkable decrease in the lattice constants has been observed in the modified Ti2AlC ceramics, and the presence of Si element in the corresponding area has been further proved by STEM. The formation and decomposition mechanisms of the Ti2(Al, Si)C solid solution have been studied via ab initio calculations. The results suggest that all the Ti2(Al1-x, Six)C structures with different Si contents are stable in the vibration aspect. However, due to the lower Gibbs energy of the competing phases, the structures with high Si content would decompose. Finally, the bulk Ti2(Al0.9, Si0.1)C has been successfully synthesized using SPS method.

    更新日期:2017-11-10
  • Role of the X and n factors in ion-irradiation induced phase transformations of Mn+1AXn phases
    Acta Mater. (IF 5.301) Pub Date : 2017-11-04
    Chenxu Wang, Tengfei Yang, Cameron L. Tracy, Jingren Xiao, Shaoshuai Liu, Yuan Fang, Zhanfeng Yan, Wei Ge, Jianming Xue, Jie Zhang, Jingyang Wang, Qing Huang, Rodney C. Ewing, Yugang Wang

    Phase transitions induced in hcp Mn+1AXn phases (Ti2AlN, Ti2AlC, and Ti4AlN3) by 1 MeV Au+ ion irradiation were investigated, over a series of ion fluences ranging from 1×1014 to 2×1016 ions cm-2, by transmission electron microscopy (TEM) and synchrotron grazing incidence X-ray diffraction (GIXRD). Irradiation-induced structural evolutions were observed using high-resolution TEM (HRTEM) imaging and selected area electron diffraction (SAED). Based on phase contrast imaging and electron diffraction pattern (EDP) simulations, the atomic-scale mechanisms for the phase transitions were determined. Transformations of the initial hcp phases to the intermediate γ-phases and fcc phases were driven by the formation of Ti/Al antisite defects and extended stacking faults induced by ion irradiation. By comparing the transformation behavior of Ti2AlN with that of Ti2AlC and Ti4AlN3 under the same irradiation conditions, using both the experimental data and first-principles calculations, the role of the X and n parameters in the radiation responses of Mn+1AXn phases were elucidated. The susceptibilities of materials in this Ti-Al-X (X=C, N) system to irradiation-induced phase transitions were determined with respect to the bonding characteristics and compositions of these MAX phases. Ti2AlC is slightly less susceptible to the radiation-induced phase transformation than is Ti2AlN, which is attributed to the stronger Ti-Al bond covalency in Ti2AlN. Ti4AlN3 is more resistant to radiation-induced phase transformations than is Ti2AlN, due to the lower Al content and lower anion vacancy ratio in the irradiation-induced solid solution phases.

    更新日期:2017-11-10
  • Ultrafast synchrotron X-ray imaging studies of microstructure fragmentation in solidification under ultrasound
    Acta Mater. (IF 5.301) Pub Date : 2017-11-03
    Bing Wang, Dongyue Tan, Tung Lik Lee, Jia Chuan Khong, Feng Wang, Dmitry Eskin, Thomas Connolley, Kamel Fezzaa, Jiawei Mi

    Ultrasound processing of metal alloys is an environmental friendly and promising green technology for liquid metal degassing and microstructural refinement. However many fundamental issues in this field are still not fully understood, because of the difficulties in direct observation of the dynamic behaviours caused by ultrasound inside liquid metal and semisolid metals during the solidification processes. In this paper, we report a systematic study using the ultrafast synchrotron X-ray imaging (up to 271,554 frame per second) technique available at the Advanced Photon Source, USA and Diamond Light Source, UK to investigate the dynamic interactions between the ultrasonic bubbles/acoustic flow and the solidifying phases in a Bi-8%Zn alloy. The experimental results were complimented by numerical modelling. The chaotic bubble implosion and dynamic bubble oscillations were revealed in-situ for the first time in liquid metal and semisolid metal. The fragmentation of the solidifying Zn phases and breaking up of the liquid-solid interface by ultrasonic bubbles and enhanced acoustic flow were clearly demonstrated and agreed very well with the theoretical calculations. The research provides unambiguous experimental evidence and robust theoretical interpretation in elucidating the dominant mechanisms of microstructure fragmentation and refinement in solidification under ultrasound.

    更新日期:2017-11-10
  • On the effects of SLM process parameters on microstructure and thermomechanical response of Ni-rich NiTi SMAs
    Acta Mater. (IF 5.301) Pub Date : 2017-11-02
    Soheil Saedi, Narges Shayesteh Moghaddam, Amirhesam Amerinatanzi, Mohammad Elahinia, Haluk E. Karaca

    Many processing parameters are involved in selective laser melting fabrication where adjustment of each reflects on the performance of the final product. This study is concerned with the effect of laser power and scanning speed alteration on the microstructure and shape memory response of Ni50.8Ti49.2. In this regard, several samples were systematically fabricated to study the microstructure, transformation temperatures, texture, and superelasticity. It is shown that different processing parameters lead to functional parts with distinct features and behavior. The samples processed with low laser power, compared to those processed with high laser power, showed significantly higher strain recovery and lower hysteresis. The samples fabricated with same energy level, but different processing parameters did not display similar results. The sample fabricated with a laser power of 100 W and scanning speed of 125 mm/s exhibited almost perfect superelasticity with a recovery ratio of 96% and strain recovery of 5.77% in the first cycle. The corresponding stabilized superelastic response demonstrated fully recoverable strain recovery of 5.5 % after 10 cycles.

    更新日期:2017-11-10
  • Coercivity enhancement of hot-deformed Ce-Fe-B magnets by grain boundary infiltration of Nd-Cu eutectic alloy
    Acta Mater. (IF 5.301) Pub Date : 2017-11-02
    Xin Tang, H. Sepehri-Amin, T. Ohkubo, M. Yano, M. Ito, A. Kato, N. Sakuma, T. Shoji, T. Schrefl, K. Hono

    The coercivity of hot-deformed Ce-Fe-B magnet was substantially improved from ∼8 ×10−4 to ∼0.7 T by the grain boundary infiltration of Nd-Cu eutectic alloy. Transmission electron microscopy have shown the formation of (NdxCe1-x)2Fe14B shell in Ce2Fe14B grains and the increase of rare earth elements in the intergranular phases after the process. The former enhances the anisotropy field of the shell region and the latter weakens intergranular exchange coupling. Micromagnetic simulations showed that the increase of the Nd content in the (NdxCe1-x)2Fe14B shell results in only a slight increase in coercivity for ferromagnetic intergranular phase. This explains the minor increment of coercivity of only ∼0.2 T for the increased amount of the Nd-Cu infiltration from 10 wt.% to 40 wt.%. For further increase of the coercivity, exchange decoupling by increasing the rare earth content in the intergranular phase is predicted to be effective.

    更新日期:2017-11-10
  • Temperature-dependence of mode I fracture toughness of a bulk metallic glass
    Acta Mater. (IF 5.301) Pub Date : 2017-11-01
    Devaraj Raut, R.L. Narayan, Parag Tandaiya, Upadrasta Ramamurty
    更新日期:2017-11-01
  • Strong and tough metal/ceramic micro-laminates
    Acta Mater. (IF 5.301) Pub Date : 2017-11-01
    Claudio Ferraro, Sylvain Meille, Julien Réthoré, Na Ni, Jerome Chevalier, Eduardo Saiz
    更新日期:2017-11-01
  • Stress-induced microcrack density evolution in β-eucryptite ceramics: experimental observations and possible route to strain hardening
    Acta Mater. (IF 5.301) Pub Date : 2017-11-01
    B.R. Müller, R.C. Cooper, A. Lange, A. Kupsch, M. Wheeler, M.P. Hentschel, A. Staude, A. Pandey, A. Shyam, G. Bruno
    更新日期:2017-11-01
  • Hierarchical aging pathways and reversible fragile-to-strong transition upon annealing of a metallic glass former
    Acta Mater. (IF 5.301) Pub Date : 2017-10-31
    Isabella Gallino, Daniele Cangialosi, Zach Evenson, Lisa Schmitt, Simon Hechler, Moritz Stolpe, Beatrice Ruta
    更新日期:2017-10-31
  • In-situ 3D visualization of composite microstructure during polymer-to-ceramic conversion
    Acta Mater. (IF 5.301) Pub Date : 2017-10-31
    Natalie M. Larson, Frank W. Zok
    更新日期:2017-10-31
  • Composition design of high entropy alloys using the valence electron concentration to balance strength and ductility
    Acta Mater. (IF 5.301) Pub Date : 2017-10-31
    Ruirun Chen, Gang Qin, Huiting Zheng, Liang Wang, Yanqing Su, YuLung Chiu, Hongsheng Ding, Jingjie Guo, Hengzhi Fu
    更新日期:2017-10-31
  • Strong converse magnetoelectric effect in (Ba,Ca)(Zr,Ti)O3 - NiFe2O4 multiferroics: A relationship between phase-connectivity and interface coupling
    Acta Mater. (IF 5.301) Pub Date : 2017-10-31
    M. Naveed-Ul-Haq, Vladimir V. Shvartsman, Harsh Trivedi, Soma Salamon, Samira Webers, Heiko Wende, Ulrich Hagemann, Jörg Schröder, Doru C. Lupascu
    更新日期:2017-10-31
  • Spatially resolved localization and characterization of trapped hydrogen in zero to three dimensional defects inside ferritic steel
    Acta Mater. (IF 5.301) Pub Date : 2017-10-31
    Waldemar Krieger, Sergiy V. Merzlikin, Asif Bashir, Agnieszka Szczepaniak, Hauke Springer, Michael Rohwerder
    更新日期:2017-10-31
  • Twin-interface interactions in nanostructured Cu/Ag: Molecular dynamics study
    Acta Mater. (IF 5.301) Pub Date : 2017-10-31
    R. Béjaud, J. Durinck, S. Brochard
    更新日期:2017-10-31
  • Strain-engineered allotrope-like bismuth nanowires for enhanced thermoelectric performance
    Acta Mater. (IF 5.301) Pub Date : 2017-10-30
    Jeongmin Kim, Min-Wook Oh, Gwansik Kim, Je-Hyeong Bahk, Jae Yong Song, Seong Gi Jeon, Dong Won Chun, Jee-Hwan Bae, Wooyoung Shim, Wooyoung Lee
    更新日期:2017-10-31
  • High frequency in situ fatigue response of Ni-base superalloy René-N5 microcrystals
    Acta Mater. (IF 5.301) Pub Date : 2017-10-30
    Steven Lavenstein, Bryan Crawford, Gi-Dong Sim, Paul A. Shade, Christopher Woodward, Jaafar A. El-Awady
    更新日期:2017-10-30
  • Relaxation and saturation of electrostriction in 10 mol% Gd-doped ceria ceramics
    Acta Mater. (IF 5.301) Pub Date : 2017-10-30
    Nimrod Yavo, Ori Yeheskel, Ellen Wachtel, David Ehre, Anatoly I. Frenkel, Igor Lubomirsky
    更新日期:2017-10-30
  • Alternative misfit dislocations pattern in semi-coherent FCC {100} interfaces
    Acta Mater. (IF 5.301) Pub Date : 2017-10-30
    S. Shao, F. Akasheh, J. Wang, Yue Liu
    更新日期:2017-10-30
  • Direct observation of the spatial distribution of primary cascade damage in tungsten
    Acta Mater. (IF 5.301) Pub Date : 2017-10-30
    D.R. Mason, A.E. Sand, X. Yi, S.L. Dudarev
    更新日期:2017-10-30
  • Surface termination analysis of stoichiometric metal hexaborides: Insights from first-principles and XPS measurements
    Acta Mater. (IF 5.301) Pub Date : 2017-10-30
    K.M. Schmidt, O. Jaime, J.T. Cahill, D. Edwards, S.T. Misture, O.A. Graeve, V.R. Vasquez
    更新日期:2017-10-30
  • The α→ω and β→ω phase transformations in Ti–Fe alloys under high-pressure torsion
    Acta Mater. (IF 5.301) Pub Date : 2017-10-28
    A.R. Kilmametov, Yu. Ivanisenko, A.A. Mazilkin, B.B. Straumal, A.S. Gornakova, O.B. Fabrichnaya, M.J. Kriegel, D. Rafaja, H. Hahn
    更新日期:2017-10-28
  • Hydrogen-modified dislocation structures in a cyclically deformed ferritic-pearlitic low carbon steel
    Acta Mater. (IF 5.301) Pub Date : 2017-10-28
    Shuai Wang, Akihide Nagao, Petros Sofronis, Ian M. Robertson
    更新日期:2017-10-28
  • Unveiling the mechanisms of cold sintering of ZnO at 250 °C by varying applied stress and characterizing grain boundaries by Kelvin Probe Force Microscopy
    Acta Mater. (IF 5.301) Pub Date : 2017-10-28
    J. Gonzalez-Julian, K. Neuhaus, M. Bernemann, J. Pereira da Silva, A. Laptev, M. Bram, O. Guillon
    更新日期:2017-10-28
  • Texture-directed twin formation propensity in Al with high stacking fault energy
    Acta Mater. (IF 5.301) Pub Date : 2017-10-27
    S. Xue, W. Kuo, Q. Li, Z. Fan, J. Ding, R. Su, H. Wang, X. Zhang
    更新日期:2017-10-27
  • Transmission electron microscopy characterization of dislocation structure in the face-centered cubic high-entropy alloy Al0.1CoCrFeNi
    Acta Mater. (IF 5.301) Pub Date : 2017-10-27
    X.D. Xu, P. Liu, Z. Tang, A. Hirata, S.X. Song, T.G. Nieh, P.K. Liaw, C.T. Liu, M.W. Chen
    更新日期:2017-10-27
  • Elastic properties and plastic deformation of TiC- and VC-based pseudobinary alloys
    Acta Mater. (IF 5.301) Pub Date : 2017-10-27
    D. Edström, D.G. Sangiovanni, L. Hultman, Ivan Petrov, J.E. Greene, V. Chirita
    更新日期:2017-10-27
  • Microstructural Deformation in Fatigued Nanotwinned Copper Alloys
    Acta Mater. (IF 5.301) Pub Date : 2017-10-27
    By Nathan M. Heckman, Matthew F. Berwind, Christoph Eberl, Andrea M. Hodge
    更新日期:2017-10-27
  • 更新日期:2017-10-27
  • In situ micromechanical testing in environmental scanning electron microscope: A new insight into hydrogen-assisted cracking
    Acta Mater. (IF 5.301) Pub Date : 2017-10-26
    Bjørn Rune Sørås Rogne, Nousha Kheradmand, Yun Deng, Afrooz Barnoush
    更新日期:2017-10-26
  • Dislocation interactions at reduced strain rates in atomistic simulations of nanocrystalline Al
    Acta Mater. (IF 5.301) Pub Date : 2017-10-25
    Maxime Dupraz, Zhen Sun, C. Brandl, Helena Van Swygenhoven
    更新日期:2017-10-25
  • Similar local order in disordered fluorite and aperiodic pyrochlore structures
    Acta Mater. (IF 5.301) Pub Date : 2017-10-23
    Jacob Shamblin, Cameron L. Tracy, Raul I. Palomares, Eric O'Quinn, Rodney C. Ewing, Joerg Neuefeind, Mikhail Feygenson, Jason Behrens, Christina Trautmann, Maik Lang
    更新日期:2017-10-24
  • Strain accumulation during microstructurally small fatigue crack propagation in bcc Fe-Cr ferritic stainless steel
    Acta Mater. (IF 5.301) Pub Date : 2017-10-23
    E. Malitckii, H. Remes, P. Lehto, Y. Yagodzinskyy, S. Bossuyt, H. Hänninen
    更新日期:2017-10-23
  • 更新日期:2017-10-23
  • Solubility in Zr-Nb alloys from first-principles
    Acta Mater. (IF 5.301) Pub Date : 2017-10-21
    Maeva Cottura, Emmanuel Clouet
    更新日期:2017-10-21
  • Synergistic effect of ultrasonic melt treatment and fast cooling on the refinement of primary Si in a hypereutectic Al–Si alloy
    Acta Mater. (IF 5.301) Pub Date : 2017-10-20
    Jae-Gil Jung, Tae-Young Ahn, Young-Hee Cho, Su-Hyeon Kim, Jung-Moo Lee
    更新日期:2017-10-20
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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