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1. On the role of the microstructure in the deformation of porous solids

   https://doi.org/10.1038/s41524-022-00840-5  

   Patnaik, Sansit; Jokar, Mehdi; Ding, Wei; Semperlotti, Fabio (July 2022, npj Computational Materials)

   Abstract This study explores the role that the microstructure plays in determining the macroscopic static response of porous elastic continua and exposes the occurrence of position-dependent nonlocal effects that are strictly correlated to the configuration of the microstructure. Then, a nonlocal continuum theory based on variable-order fractional calculus is developed in order to accurately capture the complex spatially distributed nonlocal response. The remarkable potential of the fractional approach is illustrated by simulating the nonlinear thermoelastic response of porous beams. The performance, evaluated both in terms of accuracy and computational efficiency, is directly contrasted with high-fidelity finite element models that fully resolve the pores’ geometry. Results indicate that the reduced-order representation of the porous microstructure, captured by the synthetic variable-order parameter, offers a robust and accurate representation of the multiscale material architecture that largely outperforms classical approaches based on the concept of average porosity. 

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2. Advances in characterizing and understanding the microstructure of cementitious materials

   https://doi.org/https://doi.org/10.1016/j.cemconres.2019.105806  

   Monteiro, P.J. (October 2019, Cement and concrete research)

   Progress in microstructural characterization methods is summarized. Special attention is given to advanced probes, such as X-ray imaging and spectroscopy, 1H NMR relaxometry, in-situ and high-pressure X-ray diffraction, and digital holographic microscopy. Microtomography has become a mature technique and nanotography has improved its spatial resolution significantly, particularly with the use of ptychography. The review also discusses the effect of plasticizers on the microstructure of concrete and presents a critical analysis of how organic admixtures affects the hydrates obtained from pure synthesis in saturated solutions and from more realistic hydrating systems. The addition of nanomaterials into cementitious systems modifies the microstructure of the matrix so a summary of recent research is presented. It is important to integrate the impressive progress in the characterization of the micro(nano)structure with efforts developing realistic models. Therefore, the present work gives a short but critical presentation of physical chemistry approaches that aim to link the chemical composition, texture, and microstructure of the cement hydrates. 

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3. Microstructure classification and the polycrystalline microstructure state space

   https://doi.org/10.1016/j.actamat.2025.121219  

   Miley, Dylan; Suwandi, Ethan; Schweinhart, Benjamin; Mason, Jeremy K (September 2025, Acta Materialia)

   A cornerstone of materials science is that material properties are determined by their microstructure. While the community has already developed a wide variety of approaches to describe microstructure, most of these are tailored to specific material systems or classes. This work proposes a way to quantitatively measure the similarity of microstructures based on the geometry of the grain boundary network, a feature which is fundamental to and characteristic of all polycrystalline materials. Specifically, a distance on all single-phase polycrystalline microstructures is proposed such that two microstructures that are close with regard to the distance have grain boundary networks that are statistically similar in all geometric respects below a user-specified length scale. Given a pair of micrographs, the distance is approximated by sampling windows from the micrographs, defining a distance between pairs of windows, and finding a window matching that minimizes the sum of the pairwise window distances. The approach is used to compare a variety of synthetic microstructures and to develop a procedure to query a proof-of-concept database suitable for general single-phase polycrystalline microstructures. 

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4. Effect of the initial microstructure on the pressure-induced phase transition in Zr and microstructure evolution

   Pandey, K. K.; Levitas, Valery I.; Park, Changyong; Shen, Guoyin (January 2023, arXivorg)

   The effect of initial microstructure and its evolution across the α→ω phase transformation in commercially pure Zr under hydrostatic compression has been studied using in situ x-ray diffraction measurements. Two samples were studied: one is plastically pre-deformed Zr with saturated hardness and the other is annealed. Phase transformation α→ω initiates at lower pressure for pre-deformed sample, suggesting pre-straining promotes nucleation by producing more defects with stronger stress concentrators. With transformation progress, the promoting effect on nucleation reduces while that on growth is suppressed by producing more obstacles for interface propagation. The crystal domain size reduces and microstrain and dislocation density increase during loading for both α and ω phases in their single-phase regions. For α phase, domain sizes are much smaller for prestrained Zr, while microstrain and dislocation densities are much higher. On the other hand, they do not differ much in ω Zr for both prestrained and annealed samples, implying that microstructure is not inherited during phase transformation. The significant effect of pressure on the microstructural parameters (domain size, microstrain, and dislocation density) demonstrates that their postmortem evaluation does not represent the true conditions during loading. A simple model for the initiation of the phase transformation involving microstrain is suggested, and a possible model for the growth is outlined. The obtained results suggest an extended experimental basis is required for better predictive models for the pressure-induced and combined pressure- and strain-induced phase transformations. 

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5. Effects of microstructure on the mechanical properties of Ti2AlC in compression

   Benitez, R. (January 2018, Acta materialia)

   This study investigates the effect of microstructure, specifically the grain size and TiAlx impurity, on the compressive strength and hysteretic behavior of Ti2AlC at room temperature. Given the plate-like nature of the MAX phase grains, the length and thicknesses of over 100 grains for each microstructure were measured. A Hall-Petch like relationship between compressive strength and the grain length was observed, but not such a relationship was observed with the grain thickness. Results from cyclic compression testing in combination with resonant ultrasound spectroscopy show that room temperature mechanical response of Ti2AlC can be divided into four stress regions regardless of the variation in grain size and/or amount of impurities. The grain size effect on the transition stresses for stress regions was also investigated. It was found that all transition stresses, between the different stress regions, also follow different Hall-Petch-type relationships. 

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