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The temporal evolution of microstructural features in metals and ceramics has been the subject of intense investigation over many years because deviations from normal grain growth behavior are ubiquitous and strongly dictate observed mechanical and magnetic properties. To distinguish among different grain growth scenarios, we examine the time evolution of the information content of both synthetic and experimental coarsening microstructures as quantified by both a computable information density (CID) and a spectral entropy along with selected metrics and measures of shared information and interaction strength. In these approaches, microstructural evolution is described in terms of two time series representations, namely: (1) strings and their compressed counterparts that reflect the information contained in the configuration of a system over time, and (2) the spectra of graph Laplacians that embody the information contained in a coarsening grain network. These approaches permit one to characterize dynamically evolving microstructures and to identify correlation times associated with different coarsening scenarios. Moreover, as the information content of a system is a proxy for the entropy, a thermodynamic description of grain growth is also described. [ABSTRACT FROM AUTHOR]

The post-dynamic recrystallization behavior of ultrafine-grained (UFG: 0.44 μm) cp-Ti under annealing, room temperature (RT) monotonic and cyclic loading was investigated across a range of temperatures and deformation rates wherever appropriate. By characterizing the grain and boundary structures, it was confirmed that recrystallization and grain growth occurred due to annealing (≥ 600 °C) and R = − 1 fatigue at RT. There was a noticeable 30 deg aggregation in misorientation distribution, along with the increased grain size. However, the hypothetical correlation between 30 deg aggregation and Σ13a or the other characteristic coincidence site lattice boundaries was found to be weak. The fatigue-induced grain growth is particularly intriguing for two reasons. First, the large monotonic deformation with low strain rate cannot trigger grain growth. Second, fatigue sharpened the basal intensity around the ND and caused a weaker texture component close to TD (load axis along the LD, perpendicular to the TD–ND plane). By contrast, high-temperature annealing only strengthened the UFG processing induced basal pole but without affecting its location. Novel insights into this fatigue-induced texture evolution in UFG cp-Ti has been provided. The lattice rotation during fatigue can be attributed to the combined effect of activation of prismatic ⟨ a ⟩ slip parallel to LD, and basal ⟨ a ⟩ slip perpendicular to it. The theoretically calculated stress to activate dislocation slip by assuming a non-equilibrium grain boundary state lent support to the above assertion. Moreover, the TEM observation evidently showed the characteristics of dislocation cross-slip and multiple slip in the grain interior. [ABSTRACT FROM AUTHOR]

Vacuum brazing of NbSS/Nb5Si3 composite was performed with BNi2 and BNi5 filler alloys at 1293-1423 K for 1800 seconds. The joint microstructures were examined by a scanning electron microstructure (SEM) equipped with an X-ray energy-dispersive spectrometer (XEDS), and shear test for the brazed joints was conducted at room temperature. The NbSS/Nb5Si3 joint brazed with BNi2 filler alloy at 1293 K mainly consisted of Ni3Si + Nb3Si, NiSS and borides. As the brazing temperature increased to 1423 K, Cr2Nb and NbNi phases were formed and the shear strength of the joints was increased from 180 to 253 MPa. Concerning the joints brazed with BNi5 filler at 1423 K, they exhibited an average strength of 274 MPa, and the joint micro-hardness was lower than BNi2 filler. The BNi5 filler alloy not only raised the shear strength but also decreased the joint brittleness to some extent. As a new finding in this study, 4-5 at. pct Ni had been dissolved into (Nb,Ti)SS in the NbSS/Nb5Si3 composite, providing a new insight into the design of novel specific filler material for NbSS/Nb5Si3 joining. [ABSTRACT FROM AUTHOR]

The elastic mechanical parameters of initial and pre-twisted copper wires were investigated with the aid of a self-developed micro-torsion tester. It was found that the apparent elastic shear modulus and the apparent Young tensile modulus of the copper wires decrease by 13.3 and 8.4% after pre-twist deformation, respectively. In addition, the indentation modulus also decreases as the deformation is increased. When the deformation is more than 30%, the indentation modulus of pre-twisted copper wires is smaller than that of initial copper wires. Microstructural analyses show that the elastic modulus decreases with the proportion of faults. [ABSTRACT FROM AUTHOR]

Ultrafine-grained Al-Mg-Si alloys with four different Mg/Si ratios (=0.75, 1.10, 1.48, and 1.94) were prepared by using extrusion and cold-drawing. The microstructural evolution during aging treatment was examined by using transmission electron microscopy. Hardness and electrical conductivity of the alloys were, respectively, measured before and after aging treatment. Experimental results showed that $$ \beta^{\prime\prime} $$ precipitates were dispersed within the grain interior in all the four aged alloys. Although the precipitate size was insensitive to the Mg/Si ratio, the precipitate number density as well as the inter-precipitate spacing was greatly dependent on the Mg/Si ratio. The optimized Mg/Si ratio within present work was 1.48, which led to the densest precipitation, and resulted in the highest hardness and simultaneously greatest conductivity. These findings are rationalized by considering the precipitation behaviors in the ultrafine-grained length scale and their effect on the hardness-conductivity relationship. A strengthening model was proposed for the ultrafine-grained Al-Mg-Si alloys, which accounted for the multiple contributions from grain size, dislocations, solid solution atoms, and precipitates to the hardness. The calculations were in good agreement with the experimental results. Similarly, the effect of multiple microstructural features on the electrical conductivity was also quantitatively described by adopting a model. The contribution of precipitation to both the hardness and conductivity is well demonstrated for the ultrafine-grained Al-Mg-Si alloys, which will be helpful for material design of advanced ultrafine-grained Al alloys with enhanced performance. [ABSTRACT FROM AUTHOR]

Transient liquid-phase diffusion bonding of TiAl-based alloy to TiAl intermetallics was conducted using Ti-13Zr-21Cu-9Ni (wt pct) interlayer foil. The joint microstructures were examined using a scanning electron microscope (SEM) equipped with an electron probe micro-analyzer (EPMA). The microhardness across the joint was measured and joint strengths were tested. The results show that the TiAl/TiAl joint mainly consists of Ti-rich phase, TiAl layer, α-TiAl band, and residual interlayer alloy dissolved with Al. The amount of residual interlayer at the central part of the joint is decreased with the increase of the bonding temperature, and meantime the TiAl and α-TiAl reaction bands close to the joined TiAl-based alloy become thickened gradually. Furthermore, the central part of the joint exhibits the maximum microhardness across the whole joint. The joints bonded at 1193 K (920 °C) for 600 seconds with a pressure of 2 MPa presented the maximum shear strength of 417 MPa at room temperature, and the strength of 234 MPa was maintained at 773 K (500 °C). [ABSTRACT FROM AUTHOR]

As one of the most important properties of compacted bentonite used as buffer/backfill materials, hydraulic conductivity is influenced by various factors including temperature, microstructure and suction (or degree of saturation), etc. Based on the readily available results of both temperature-controlled water-retention tests and unsaturated infiltration tests under confined (constant volume) conditions, influences of temperature and microstructure variations on unsaturated hydraulic conductivity of the compacted Gaomiaozi (GMZ01) bentonite were analyzed. Then, a revised unsaturated hydraulic conductivity model considering temperature effects and microstructure changes was developed. With this proposed model, prediction and comparison were made on the unsaturated hydraulic conductivity of the compacted GMZ01 bentonite at 20 °C. Results show that water-retention capacity of compacted GMZ01 bentonite decreases as temperature increases and the degree of the temperature influence depends on suction. Under confined conditions, influence of hydration on microstructure of compacted GMZ01 bentonite depends on pore size. The proposed model can well describe the variations of unsaturated hydraulic conductivity with suction at different temperatures. However, further improvement of the proposed model is needed to account for the phenomenon of inter-aggregate pores clogging that occurred at the initial stage of hydration of compacted GMZ01 bentonite under confined conditions. [ABSTRACT FROM AUTHOR]

This article focuses on the influence of iron ion irradiation on the aqueous corrosion resistance of zircaloy-4. Materials irradiated with energetic particles respond by undergoing changes in the internal microstructures, phase distributions, dimensions, mechanical and corrosion properties. Heavy ions in the MeV energy range impart energy to the atoms of the target materials and produce a displacement cascade consisting of highly localized interstitials and vacancies. There is a growing interest in the effect of irradiation on the structure and the corrosion property of zirconium alloys in recent years.