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This work demonstrates that large pores promote abnormal grain growth, a commonly observed but poorly understood behavior. To investigate this phenomenon, calcia doped aluminum oxide is used as a model ceramic because of its known propensity for abnormal grain growth. Controlled porous microstructures are fabricated using polymer microspheres with nominal diameters approximately an order of magnitude larger than the average grain diameters. Electron backscattered diffraction maps indicate that the introduction of large pores (∼3 vol.%) promotes abnormal grain growth, increasing the total abnormal grain area by more than 60 % when sintered at 1600 °C for 4 h in air. The differences between samples with and without large pores provide insight into the initiation of abnormal grain growth, which is needed to predict microstructure evolution in complex systems with such defects. [Display omitted] [ABSTRACT FROM AUTHOR]

Enhanced Hastelloy alloy diffusion bonding was investigated via introducing nanostructured Ni surface layer. Because the bonding temperature was significantly higher than the nanostructured Ni destabilization temperature, rapidly complete recrystallization and dramatic grain growth occurred. The beneficial effect of high-density short-circuit defects provided by nanocrystalline on enhanced diffusion ought to be limited. However, significantly accelerated diffusion was still observed in the joint. The unique contribution of the nanostructured layer in evolving microstructure is to promote the formation of diffusion-induced recrystallization at the interface, where solute elements could diffuse rapidly along the moving boundaries at a rate several orders of magnitude larger than static grain boundaries. The retained ultrafast atomic diffusion paths result in a bonding temperature of 250 °C–350 °C lower than the conventional diffusion bonding approach. The tensile strength of the achieved joint reached 833 MPa, which was nearly equal to that of the as-delivered substrate. [Display omitted] [ABSTRACT FROM AUTHOR]

The effects of initial twinned microstructure on the grain growth behavior of four sputtered nanotwinned copper alloys were compared. As-deposited films were characterized by transmission electron microscopy and the microstructural evolution of the annealed samples was investigated through electron backscatter diffraction. Texture showed a pronounced effect, where films with strong {111} textures exhibited abnormal grain growth that was not observed in a randomly textured film. Additionally, the stability induced by twin boundaries appears to be limited, as the excess energy generated by a large twin density could drive the early onset of abnormal grain growth and recrystallization. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In this work anisotropic motion of disconnections at general grain boundaries in SrTiO 3 was detected in-situ at 1030°C, 1040°C and 1050°C using transmission electron microscopy. The same anisotropic motion of ledges and terraces at the surfaces of SrTiO 3 was detected in-situ. These results corroborate previous ex-situ studies on disconnection motion in SrTiO 3 , and experimentally confirm that anisotropic disconnection motion is the mechanism of grain growth. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Thermomechanical behavior of an ultrafine-grained nickel-yttrium alloy has been investigated through quasi-static (10−4 s−1) and high temperature creep experiments under uniaxial compression along with post-deformed transmission electron microscopy (TEM) characterization. While the alloy possesses a quasi-static flow stress of ~1255 MPa at room temperature, the flow stress drops by about 80% at 873 K. TEM analysis showed negligible average grain growth over the entire temperature range tested. Furthermore, the alloy showed exceptional steady–state creep behavior owing to the relative stability of the grain size and interactions between dislocations/grain boundary and inclusions/dispersoids. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The influence of sample size on microstructure, density, and onset temperature of the flash event was investigated for 3 mol% yttria-stabilised zirconia (3YSZ). Pellet samples with different height and constant diameter were flash sintered under an AC electric field. The larger the samples were, the lower was their flash onset temperature. Furthermore, a more heterogeneous microstructure was verified on larger samples followed by lower density. The influence of the samples' height on the thermal runaway and the thermal gradient within the samples are discussed as responsible for these effects. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We reported the fabrication of densely twinned Cu films with highly (211) texture developed from the annealing of <111>-oriented nanotwinned copper (nt-Cu) films. During the annealing at 300 °C, abnormal grain growth occurred in the nt-Cu film and resulted in a microstructure dominated by the anomalously large <211>-oriented grains. Moreover, densely-intersected annealing twin bands with <221>, <611>, and <931> orientations are embedded in the large <211> grains. The measured annealing twin density is 0.2 µm−1, which is highest among the reported values in previous literatures with similar grain size. Extensive multiple twinning process may occur during the annealing to form the unique microstructure. We reported the fabrication of densely twinned Cu films with highly (211) texture developed from the annealing of <111>-oriented nanotwinned copper (nt-Cu) films. During the annealing at 300 °C, abnormal grain growth occurred in the nt-Cu film and resulted in a microstructure dominated by large <211>-oriented grains embedded with densely-intersected annealing twin bands with <221>, <611>, and <931> orientations, as shown in Fig (a) below. The measured annealing twin density is 0.2 µm−1, which is highest among the reported values in previous literatures. The boundaries shown in red in Fig (b) represent the ∑3 twin boundaries. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Influence of energetically-preferred quadrijunctions on the kinetics of grain growth in textured two-dimensional duplex-microstructure is investigated in this work. A multiphase-field approach, wherein individual grains are associated with the constituent phases of the microstructure, is adopted for the present study. Different forms of anisotropy, phase-dependent (E α ≠ E β) and -independent (E α = E β), established by appropriately varying grain boundary energies are considered. While being consistent with the analytical predictions, and existing studies, the present investigation unravels that, irrespective of the nature of anisotropy, the kinetics of the microstructural evolution in duplex polycrystalline system linearly decreases with increase in the density of quadrijunctions. [ABSTRACT FROM AUTHOR]

Using our homemade tensile device inside a transmission electron microscope, we in-situ investigated the deformation behaviours of the nano-twinned nanocrystalline Au thin-films with thickness of ~15 nm and average grain size of ~16 nm. Our extensive in-situ observation studies reveal that the deformation of the nano-twinned nanocrystalline Au thin-film was dominated by the cooperative grain boundary sliding and migration, which were rarely observed in the previous reports. Meanwhile, our statistic shows that the nano-twins tended to promote further stress-driven grain growth, and the promotion became more remarkable for the nano-twinned grains that were located at the crack tips. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Normal grain growth in thin films attached to a substrate has been considered. It has been shown that shear-coupled grain boundary migration results in the build-up of elastic stresses in the film. A semi-quantitative model of grain growth combining the elements of disclinations theory with the Burke-Turnbull model of normal grain growth has been proposed. It has been shown that shear-coupled grain boundary migration may lead to stagnation of normal grain growth, whereas for high coupling factor values, the grains in the film do not grow at all. Finally, the mechanisms of stress relaxation enabling some grain growth are discussed. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In 3D IC technology, when the size of the micro-bump solder joint is reduced to 10 µm, the scallop-type Cu 6 Sn 5 grains on opposite sides of the joint can interact directly by contacting each other during the solid–liquid interdiffusion reaction. Upon contact, an extremely rapid grain growth of the scallops occurs. We propose that the liquid solder wets the grain boundary between scallops and provides an extremely fast kinetic path of liquid channel for grain growth. The width of the liquid channel has been estimated to be about 1.5 nm. This is a unique phenomenon observed in micro-bump solid joints. The intermetallic compound (IMC) of Cu 6 Sn 5 on the opposite sides of the joint can interact directly by touching each other during the solid–liquid interdiffusion (SLID) reaction, as shown in Fig. (a) and (b). Upon touching, an extremely rapid grain growth of the IMC occurs, as seen in Fig. (c). We propose that the liquid solder wets the grain boundary of IMC and provides an extremely fast kinetic path of liquid channel for grain growth, as illustrated in Fig. (d). It is a unique phenomenon in solid joint technology when the joint becomes small. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We demonstrate the sensitivity of complexion time-temperature-transformation (TTT)-diagrams to composition and grain size in Eu-doped MgAl 2 O 4. 100 ppm and 500 ppm Eu-doped MgAl 2 O 4 undergo the same complexion transition, which causes abnormal grain growth, but exhibit different nucleation and grain growth rates. The Eu content per grain boundary area (Eu/GBA) was calculated for various heat treatments using a simple model based on average grain size. Despite their differences, a common Eu/GBA is calculated at the onset of abnormal grain growth. This common grain boundary excess has important implications for complexion TTT-diagrams and provides a new metric for predicting abnormal grain growth. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The impact of faceting on grain growth was approached by model experiments in NiO–MgO. Grain growth rates were found to be 10 times higher in NiO compared to MgO. As the self-diffusion acoefficients differ by a factor of 250, grain growth in NiO is unexpectedly slow compared to MgO. Recently, the movement of steps was identified as the atomic mechanism of grain boundary migration. According to the equilibrium crystal shape, grain boundaries in NiO are more faceted. The faceted grain boundaries of NiO have fewer steps at the grain boundaries resulting in a relatively lower mobility. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We investigate the effect of direct electric current (DC) on grain growth in 100 nm thick iron-carbon films with carbon concentrations between 0.7 to 4.4 at%. The application of DC-current during annealing at 550°C confirms the expected transport of carbon in the direction of the electric current and the unexpected formation of elongated, abnormally large carbide and ferrite grains along the current direction in the carbon-rich regions. The formation of elongated grains is explained by electromigration-induced carbon flux divergences that result from the carbide precipitates. This presents a possible scenario for controlling microstructure evolution in iron by using DC electric currents. Changes for alternating current (AC) pulses had been observed before. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In this work, the effect of ZrO 2 -doping on the microstructure evolution and phase change of Tb 3 Al 5 O 12 (TAG) ceramics has been investigated systematically. Except for the transformation of Zr4+–Zr3+, a novel phenomenon is discovered in the final stage of sintering that a second phase of ZrO 2 is discharged to the surface of samples at the sintering temperature higher than 1550 °C, which is accompanied with a largely promoted grain growth at the same time. The discharge behavior is considered to contribute to the enhanced optical quality of TAG ceramics for the decreasing residual impurity in grain boundaries. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Electromigration (EM) is a major failure mode in electronic interconnections, which is commonly made of Ag, Cu, and their alloys. Herein, a single- and two-phase Ag Cu alloys were subjected with current density of 4 × 105 A/cm2 for in situ microstructural and crystallographic characterizations. Anomalous grain growth and the formation of cord-like grains with an aspect ratio over 1000 and asymmetrical hillock/voids clusters were found. These abnormal morphological evolutions were resulted from the electron flow-induced lattice strains, which was inversely correlated with the lifespan of interconnection. Multi-phase alloys are less resistant to EM due to the unbalanced electron flow-induced strains. Unlabelled Image [ABSTRACT FROM AUTHOR]

The mechanical properties of cemented carbides can be tuned by controlling WC grain coarsening and the simultaneous growth of the binder pocket size during the sintering. So far, bulk studies considering this phenomenon are scarce, but here, we report the first very-small angle neutron scattering (VSANS) study on cemented carbides. VSANS is supplemented with electron backscatter diffraction (EBSD) and the microstructural refinement by increasing V-doping (0, 0.02, 0.22, and 0.76 wt%) is quantified. The capability of VSANS as a non-destructive bulk probe for cemented carbides is shown, paving way for forthcoming in-situ studies. Unlabelled Image [ABSTRACT FROM AUTHOR]

Two transparent AlON ceramics substrates were successfully pressureless joined at 1880 °C for 80 min by using a powder interlayer of parent material. The grains on the interface of the joint were simultaneously shared by both interlayer and substrates due to grain growth and coalescence, which can evidently be categorized as thermal diffusion bonding under pressureless condition. The identical phase assemblage and microstructure for both interlayer and substrates lead to a bending strength of the joint (229.1 MPa) nearly equal to that of substrates, which is much higher than that of the reported AlON joints. Unlabelled Image [ABSTRACT FROM AUTHOR]

The microstructure and texture evolution during static recrystallization of Mg-Nd alloys were investigated. Depending on the third alloying element added into Mg-Nd alloy, either Al or Zn, diverse textures are formed during recrystallization annealing. The rolled Mg-2Nd-1Zn sheet shows a high activity of prismatic slip and the formation of a weak texture with basal pole spread in the sheet transverse direction. In contrast, a strong texture with a basal pole spread in the rolling direction was formed in the Mg-2Nd-1Al sheet. An equivalent growth of the recrystallized grains at the early annealing stage retains their orientations during grain growth. Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Atomistic simulations of radiation damage uncover how grain boundaries (GBs) migrate and coalesce under irradiation in bicrystalline Cu. Planar GB migration biased by defect cluster-mediated attraction first leads to slow and steady motion. Subsequently, adjoining GBs coalesce into curved surfaces, where curvature-driven migration with a velocity three orders of magnitude higher than that of a planar boundary dominates motion, triggering rapid grain growth. This study reveals the atomistic mechanisms of radiation-induced grain growth, and has practical implications towards engineering radiation-tolerant nanostructures. Graphical Abstract [ABSTRACT FROM AUTHOR]

Abstract Highly transparent Zr:TAG (Zr:Tb 3 Al 5 O 12) ceramics were obtained by the solid-state reaction after vacuum sintering (up to 82.04% at 1064 nm). Laser-induced damage threshold of Zr:TAG ceramics were measured and compared to TGG (Tb 3 Ga 5 O 12) crystal and ceramic. Improved optical quality and exaggerated grain growth of TAG ceramics were observed at the same time due to ZrO 2 -doping, which is argued to be related to the valence change of Zr4+ → Zr3+ at high temperature. A detailed analysis of possible mechanisms was presented and discussed. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Significant grain growth assisted by a martensitic transformation near or below room temperature was found in a nanocrystalline Ti-50.8Ni (at.%) alloy. Significant grain growth was observed when thermally- or stress-induced B2 ↔ R ↔ B19′ (B2: parent phase, R and B19′: two types of martensite phases) martensitic transformation is repeated while not when B2 ↔ R transformation is repeated. This implies that martensitic transformation to and from the B19′ martensite phase assist the grain growth. Transmission electron microscope observations indicate that migration of grain boundaries could be the main mechanism for the grain growth. Graphical abstract Growth of B2 parent phase grain assisted by martensitic transformation in a nanocrystalline Ti-50.8Ni (at.%) shape memory alloy. Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Employing CaCO 3 as sintering additive, highly transparent aluminum oxynitride (AlON) ceramics were pressurelessly fabricated from AlON powder at 1870 °C during150 min. The transmittance of the AlON doped with 0.3–0.4 wt% CaCO 3 is up to 83–85% at ~3700 nm for 2 mm thickness samples, and their transmittances are consistently higher than that of the AlON doped with the ideal amount of Y 2 O 3 at wavelength ranging from 200 nm to 6000 nm. The AlON doped with CaCO 3 exhibits the transmittance of 71% at 4800 nm (typical band for infrared targeting), which is higher by 6% than that of the doped Y 2 O 3. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

The coefficient of thermal expansion (CTE) as measured by dilatometry of electroformed nanocrystalline Ni-32at%Co macro-defect free sheet metal up to 500 °C can be separated into three regions. Below 185 °C, the nanocrystalline material's CTE is similar to its polycrystalline counterpart. Between 185 and 310 °C, the CTE of the nanocrystalline material plateaus, then drops at temperatures above 310 °C due to volume shrinkage induced by different grain growth stages. The grain boundary excess volume (BEV) was determined to be between 0.20–0.24 nm. In addition, it is shown that simple digital caliper measurements are a reliable technique to estimate BEV for specimens with grain boundaries being the main defect. [Display omitted] [ABSTRACT FROM AUTHOR]

Solute segregation is used to limit grain growth in nanocrystalline metals, but this stabilization often breaks down at high temperatures. Amorphous intergranular films can form in certain alloys at sufficiently high temperatures, providing a possible alternative route to lower grain boundary energy and therefore limit grain growth. In this study, nanocrystalline Ni W that is annealed at temperatures of 1000 °C and above, then rapidly quenched, is found to contain amorphous intergranular films. These complexions lead to a new, unexpected region of nanocrystalline stability at elevated temperatures. [ABSTRACT FROM AUTHOR]

An electrical current upon flash sintering experiments modifies the defect chemistry of corundum and causes the formation of color centers (F-centers), consisting of discharged oxygen vacancies. This phenomenon interacts with the diffusion kinetics in the anodic region and promotes abnormal growth of some grains which reach several hundreds of micrometers in just few minutes, the grains being strongly oriented orthogonally to the current flow. [ABSTRACT FROM AUTHOR]

Microstructure evolution in non-conserved and volume-conserved isotropic two-phase grain structures, with equal interfacial energy for all interfaces and equal volume fractions of the two-phases, is compared based on large-scale phase-field simulations. Two important observations are as follows: (1) the growth mechanism has a larger effect on the grain size distributions of the two alloys than on their grain topology distributions; (2) the growth rate and normalized grain size relation of the grains per topological class are much more scattered for the conserved system than the non-conserved system. [ABSTRACT FROM AUTHOR]

The thermodynamic dissipation-based approach, being one of the approved effective methods for treatment of grain growth, is refined by accounting for dissipation due to translational motion of individual grains during grain growth. The present model introduces an interaction function correlating the velocity of translational motion and the rate of growth for individual grains. The comparison of results of simulations based on the present model with existing phase-field simulations indicates that about 1/4 to 1/3 of the driving force is dissipated by translational motion of grains lowering the grain growth kinetics and changing of the steady state grain radii distribution function. [ABSTRACT FROM AUTHOR]

We investigate the effect of electrical current density below the electromigration failure limit in nanocrystalline zirconium thin films using in-situ Transmission Electron Microscope and molecular dynamics simulation. At least one order of magnitude higher growth was seen at current density of 8.5 × 10 5 A/cm 2 (Joule heating temperature 710 K) in 15 min compared to conventional thermal annealing at 873 K for 360 min. Simulation results support our hypothesis that the concurrent effects of electron wind force and Joule heating specifically target the grain boundaries, producing much higher grain boundary mobility compared to high temperature annealing alone. [ABSTRACT FROM AUTHOR]

The existence of a ‘Hillert regime’ in 3D normal grain growth, where the grain size distributions (GSDs) at different time-steps match the Hillert distribution during parabolic grain growth, is investigated for different initial GSDs using large-scale phase-field simulations. The short-lived ‘Hillert regime’ was present in the early-stage only in few cases. The GSDs obtained at a later-stage for all cases are self-similar over long period; independent of the initial GSDs; and wider than the Hillert distribution. Also, the topological properties in the ‘Hillert regime’ were different from that in the later-stage self-similar regime. [ABSTRACT FROM AUTHOR]

Microstructural changes in nanocrystalline materials are driven by their high grain boundary density and greater mobility at elevated temperatures. For instance, segregation, precipitation, and grain growth become active as the temperature increases. The potential of nanometallic multilayers as a route to synthesize nanostructures is explored examining the microstructural evolution of Hf-Ti nanometallic multilayers through differential scanning calorimetry and characterization at different temperatures. Thermodynamic and kinetic calculations were performed to understand the observed transitions. This study presents a guide to microstructural changes in nanometallic multilayers which can be used to develop new nanocrystalline systems. [ABSTRACT FROM AUTHOR]

This study employed a TEM-based automated crystal orientation mapping technique that enables orientation mapping with nanoscale spatial resolution. This nanoscale orientation mapping technique was employed to study thermally-assisted grain growth and to quantify the attendant formation of nanotwins and twin junctions in nanocrystalline Cu. The grain size increased from 29 ± 14 nm to 57 ± 22 nm and the fraction of twin-containing grains increased from 0.18 to 0.70. Close inspection of the twins and twin junctions captured within orientation maps documented a frequency of junctions that was remarkably consistent with previous molecular dynamics predictions. [ABSTRACT FROM AUTHOR]

To study the role of chemical composition on the resistivities of grains and grain boundaries (GB) for dilute Fe-alloyed Cu thin films, Cu films with grain sizes varying over three orders of magnitude and compositions of 0.025 and 0.25 at.% Fe were prepared by magnetron co-sputtering. Character, morphology and compositions of bulk and GBs were studied using electron backscatter diffraction, transmission electron microscopy and atom probe tomography, respectively. The specific resistivities of both individual GBs and within grains were obtained through local electrical measurements assisted by micromanipulation in situ within a scanning electron microscope. In addition, global resistivity characterisation of the thin films allowed for calculation of the GB reflection coefficient. A decoupling of GB and grain interior resistivities is found with alloying, where the GB resistivity increases by an order of magnitude while the grain interior is affected only to a minor extent in comparison. [Display omitted] [ABSTRACT FROM AUTHOR]

Modeling the spark plasma sintering of ceramics can be a very time-consuming task requiring high temperature sintering tests with fully dense/porous specimens in different configurations. Final stage sintering requires a particular attention as the densification kinetic is closely related to the grain growth phenomenon. In this work, we describe a combined master sintering curve and regression method which is able to determine all sintering model parameters. The original approach of this study lies in the possibility to estimate the grain size curve with the grain growth disturbance on the densification kinetics at the final stage. The model and grain size curve estimation reproduce well the experimental data points. [Display omitted] [ABSTRACT FROM AUTHOR]

The thermal stability of multilayered NiFe specimens was investigated by using scanning differential calorimetry. Grain growth was found occurred at similar temperature, around 400 °C. Four different heating rates were selected and the activation energy was determined by using modified Kissinger analysis. The activation energy for grain growth is significantly higher than the activation energy for diffusion processes, in the bulks and grain boundaries that control grain growth. [ABSTRACT FROM AUTHOR]

The effects of nano-precipitation on stress-induced martensitic transformation (SIM) in Fe 43.5 Mn 34 Al 15 Ni 7.5 shape memory alloy wires were investigated. It was shown that a large grain size to wire diameter ratio, i.e. an oligocrystalline structure, is necessary to obtain superelasticity. The critical stress for SIM and tensile strength at room temperature increase with aging time at 200 °C without loss of superelasticity. A superelastic strain of 6.7%, with tunable transformation stress level as high as 600 MPa, and a low stress hysteresis, was obtained in the aged wires. [ABSTRACT FROM AUTHOR]

Phase pure Na 2 Zn 5 (MoO 4 ) 6 ceramic is prepared by solid state ceramic route and the structural characterisations have been done using powder X-ray diffraction and laser Raman spectroscopy. Na 2 Zn 5 (MoO 4 ) 6 ceramics exhibited a maximum density of 3.73 g/cm 3 at 590 °C together with ԑ r = 8.1, Q u × f = 35,800 GHz and τ f = − 95 ppm/ °C at microwave frequencies. Scanning electron micrographs of the sintered samples show exaggerated grain growth, which is correlated with the microwave dielectric properties. The chemical compatibility between Na 2 Zn 5 (MoO 4 ) 6 ceramic and metal electrode has been ascertained using energy dispersive X-ray spectroscopy. [ABSTRACT FROM AUTHOR]

The study of grain growth kinetics in nano-grained UO 2 samples is reported. Dense nano-grained UO 2 samples with well-controlled stoichiometry and grain size were fabricated using the spark plasma sintering technique. To determine the grain growth kinetics at elevated temperatures, a synchrotron wide-angle X-ray scattering (WAXS) study was performed in situ to measure the real-time grain size evolution based on the modified Williamson-Hall analysis. The unique grain growth kinetics of nanocrystalline UO 2 at 730 °C and 820 °C were observed and explained by the difference in mobility of various grain boundaries. [ABSTRACT FROM AUTHOR]

The effect of Mn substitution with 1 at.% additions of Co, Fe, Cu, and Cr on the properties of a polycrystalline Ni 49.8 Mn 28.5 Ga 21.7 magnetic shape memory (MSM) alloy after heat-treatment is examined. Doped alloys exhibit a single-phase five-layered modulated martensite structure at ambient temperature and a slight increase in martensite transformation temperatures compared to the non-doped alloy, without a substantial alteration of the Curie temperature. Cr addition decreases the grain size, while additions of Co, Fe, and Cu increase the grain size, as compared to the non-doped alloy. Particularly, Co addition leads to extreme grain growth, transforming the grain structure from polycrystalline to oligocrystalline with an average grain diameter of 2.83 mm. The Co-doped alloy demonstrates an MSM effect with a low switching field of H <0.15 T and a twinning stress of 1 MPa, which is a promising composition for use in polycrystalline-based MSM research and applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, the self-ion irradiation behavior of nanocrystalline copper-tantalum alloys was investigated. In particular, the microstructural evolution of Cu-3at.%Ta and Cu-10at.%Ta was evaluated under the fluence of 2 × 1017 ions/cm2 of 4 MeV Cu-ions at different temperatures. Results revealed that despite the ability of Cu-10Ta to reprecipitate new nanoclusters and thereby increase the sink density by ∼17%, it undergoes significant microstructural evolution. On the other hand, Cu-3Ta exhibits a relatively more stable microstructural response and 3.5 times less swelling over the same conditions. This result illustrates the premise that irradiation and deformation may be coupled to stabilize/rejuvenate Ta-nanoclusters in extreme-environments. [Display omitted] [ABSTRACT FROM AUTHOR]

High-energy x-ray diffraction microscopy (HEDM) nondestructively maps microstructures in 3D, allowing for the same grains and boundaries to be tracked over time during annealing experiments. Here, HEDM was applied to observe grain growth in strontium titanate. These results are compared to a 3D isotropic grain growth simulation that starts from the same initial microstructure to identify potentially unknown grain boundary migration mechanisms. During the simulation, grain growth behaves as expected: the change in grain volume is correlated with the number of neighbors, and the grain boundary velocity is correlated with its local curvature. Experimentally, however, flat boundaries were found to move faster than curved boundaries, and 37% of all measured boundaries move in the direction opposite to their curvature. These unexpected observations suggest that, in materials with anisotropic grain boundary properties, mechanisms other than curvature-driven boundary migration play a role in the minimization of interfacial energy. [Display omitted] [ABSTRACT FROM AUTHOR]

Instantaneous high temperature improved the low-temperature sintering efficiency of the un-doped MgB 2 superconductor, and the MgB 2 was rapidly synthesized at 600 °C for only 2 h. In addition to the refinement of MgO impurity particles, the sudden high temperature induced defects within the MgB 2 grains, e.g. twinning crystal, and the J c performance is therefore significantly enhanced, about 2.2 × 10 3 A·cm − 2 at 4 T for bulk sample. Differed from the two-dimensional nucleation growth mode of the MgB 2 grains in the high-temperature sintered un-doped sample, the low-temperature sintered MgB 2 grains accord with the dislocation growth mechanism, relying on the thermal-stress-triggered twinning crystal. [ABSTRACT FROM AUTHOR]