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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]

Many studies have shown that carbon nanotubes (CNTs) have excellent strengthening effect as a reinforcement in pure aluminum (Al). However, it is unknown that whether such merit can be also achieved in strong Al alloys for achieving higher-strength Al matrix composites. In this study, CNTs were incorporated into pure Al and a high-strength Al alloy (AA5083) via the same powder metallurgy route. Results showed that during the dispersion stage, the high energy ball milling process caused different amounts of deformation to pure Al and AA5083, which led to a better dispersion state of CNTs in powders and composites of pure Al. Although the two composites had the same tensile strength coincidentally, the reinforcing effect of CNTs in pure Al composite was more than five folds larger than that in AA5083, suggesting a strong matrix effect on strengthening behavior of CNTs in Al matrix composites. The present finding may show significant guidance for the optimization of fabrication processes and development of high-performance CNTs/Al composites. [Display omitted] • Strengthening behavior of CNTs/pure Al and CNTs/AA5083 composites were compared. • The dispersion states of CNTs in the CNTs/pure Al and CNTs/AA5083 composites were compared especially. • The reinforcing efficiency of CNTs under poor dispersion state and fine dispersion state were discussed. [ABSTRACT FROM AUTHOR]

The microstructure control and refinement in length scale are pursued in the development of next generations of Pb-free solder alloys with high reliability in harsh environments. In the present work, the influences of nucleation undercooling, as brought by solder ball size, over the microstructure evolution and nanomechanical behavior in Sn-3.0Ag-0.5Cu (wt%) Pb-free solder alloys, have been quantitively investigated using Differential Scanning Calorimeter (DSC), Scanning Electron Microscopy (SEM) and nanoindentation. The results reveal that undercooling increases with the decrease of solder ball size. The frequency of interlaced grain microstructure was significantly increased in 200 μm balls, with a further increase of undercooling by ∼10 K. The volume fraction of primary β-Sn increased with larger undercooling, leading to microstructure refinement with a finer spacing of both β-Sn dendrite and eutectic Ag 3 Sn. The length scale of refinement is on the order of ∼2, as the solder ball size reduced from 650 μm to 200 μm. Nano-hardness and creep resistance increase with smaller ball size and larger undercooling. Nano-hardness values are relatively higher as more eutectic regions being measured due to the strengthening effect of finer and denser eutectic Ag 3 Sn, and also the refinement of interlaced β-Sn grains. The creep exponent is insensitive to the loading force or solder ball size. The variation of nanomechanical deformation behavior was reduced in the 200 μm balls, due to the substantial microstructure refinement, while the dominant creep mechanism stays as the dislocation climb for various solder ball sizes. • Sn3.0Ag0.5Cu ball solidification is nucleation controlled with size independency. • More hypo-eutectic and refined microstructure formed with larger undercooling. • Interlaced microstructure becomes more frequent via a deeper undercooling by 10 K. • The fine eutectic Ag 3 Sn enhances the nano-hardness and creep properties of solder. • Nanomechanical data variation was reduced with refined homogeneous microstructure. [ABSTRACT FROM AUTHOR]

[Display omitted] • 450 °C very-high-cycle fatigue of Ti60 and effect of cyclic pre-strain. • S-N curve with duality characteristic. • Surface cracking mechanism competes with the subsurface one in the life regime of 107. • Local grain texture is important for the subsurface cracking at low stress. • Cyclic pre-strain increases the fatigue strength of ∼100 MPa, despite duality remains. High-cycle and very-high-cycle fatigue at 450 °C in near-α titanium with bi-modal microstructure are investigated. Stress-life duality appears with one data group spanning from 105 to 107 and the other from 107 to 109 cycles, characterized by surface and subsurface cracking, respectively. Misfit strain induced by the high misorientation of a particular primary α-grain relative to its surroundings, termed as local texture, promotes the subsurface fatigue-crack initiation. Fatigue strength increases up to 100 MPa owing to cyclic pre-strain at 450 °C, but the duality remains. Strain hardening by activation of prismatic slip is responsible for the improved fatigue strength. [ABSTRACT FROM AUTHOR]

• As-built samples have shown increased α-lath width along the build direction. • HIPing helped to remove the graded microstructure and increased α-lath width by 50%. • Graded microstructure in as-built samples led to graded cyclic softening behaviour. • As built samples from the bottom showed 38% lower plastic strain range than the top. • Application of HIPing reduced the graded cyclic deformation behaviour. Cyclic deformation and damage mechanisms in electron-beam-melted Ti-6Al-4V are investigated. As-built samples exhibit a graded microstructure over the height of 120 mm, with samples from the top having larger α-laths and higher plastic strain. After HIPing, the α-lath width is greater, with reduced grain misorientation, and lower microstructural and property gradients. In both conditions, the observed cyclic softening is dominated by a monotonic reduction in the friction stress and an increase in grain misorientation, suggesting the lath structure progressively fragments into smaller grains. As-built samples show typically lower fatigue life due to crack initiation from gas pores and lack-of-fusion defects. [ABSTRACT FROM AUTHOR]

• The ambient texture was determined by the parent austenite texture and variant selection. • The major prior austenite texture were B {0 1 1}[2 1 1] and {0 1 1}[2 2 3]. • The ambient textures were promoted by strong Bain group and variant selection. • The austenite texture of Cu, Goss and S orientations were not found. The ambient textures and their evolutions in an 800 MPa grade hot rolled low carbon micro-alloyed complex steel were analyzed. The prior austenite were firstly reconstructed and subsequently, determined the prior austenite texture unambiguously and calculated the corresponding variant fractions. It was found that the ambient texture was concurrently determined by the parent austenite texture and variant selection during the following phase transformation. The major prior austenite texture were B {0 1 1}〈2 1 1〉 and {0 1 1}〈5 3 3〉. They primarily give rise to the ambient transformation γ texture of {1 1 1}〈 2 3 - 1 〉, {1 1 1}〈2 5 - 3〉 and {1 1 1}〈 1 - 2 - 3 〉 by the selection of B1 or B2 group and α texture of {0 0 1}[1 1 0] by the selection of B3 group. The austenite textures of {2 1 0}〈3 6 1〉, {6 3 1}〈3 5 3〉, {6 1 8}〈1 2 1〉, also contribute to the overall transformation texture by strong variant selection. However, the austenite texture of Cu {1 1 2}〈1 1 1〉, Goss {1 1 0}〈0 0 1〉, S {1 2 3}〈6 3 4〉 orientations that were commonly transformed in the previous researches were not found in this steel. [ABSTRACT FROM AUTHOR]