Acta Materialia最新文献

{"title":"The influence of sodium oxide and temperature on the atomic structure and mechanical properties of silicate glasses: A molecular dynamics and Brillouin light scattering study","authors":"Hicham Jabraoui , Thibault Charpentier , Jean-Marc Delaye , Yann Vaills","doi":"10.1016/j.actamat.2025.121565","DOIUrl":"10.1016/j.actamat.2025.121565","url":null,"abstract":"<div><div>This study investigates the structural and mechanical properties of sodium silicate glasses (Na<sub>2</sub>O-SiO<sub>2</sub>) based on Na<sub>2</sub>O content (5–35 mol%) and temperature (300–600 K) using Brillouin Light Scattering (BLS) spectroscopy and Molecular Dynamics (MD) simulations. Key structural parameters are examined to understand how composition, temperature, and network structure interact. The results reveal significant network depolymerization as the Na<sub>2</sub>O content increases, driven by Na-rich clusters that depend on the amount of Na<sub>2</sub>O. Na diffusion is also studied and connected to its Voronoi volume. At low Na<sub>2</sub>O, Na atoms are associated with larger Voronoi volumes, making diffusion easier due to thermal agitation and densification of the silicate network. At high Na<sub>2</sub>O, Na atoms occupy smaller Voronoi volumes, requiring more energy to diffuse due to congestion of the Na sub-network and rigidification. Elastic constants (<span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>11</mn></mrow></msub></math></span>, <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>44</mn></mrow></msub></math></span>) show different patterns: <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>11</mn></mrow></msub></math></span> decreases below 20% Na<sub>2</sub>O but increases at higher concentrations due to depolymerization and densification of the Na network, while <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>44</mn></mrow></msub></math></span> steadily decreases, showing less resistance to shear due to the increasing presence of non-bridging oxygens (NBOs) (with only a minor contribution from free oxygens, FOs, whose concentration remains very low, <span><math><mo>∼</mo></math></span>0.6%). Experimental results also show that at low Na<sub>2</sub>O (<span><math><mo><</mo></math></span>11%–12% for <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>11</mn></mrow></msub></math></span>, <span><math><mo><</mo></math></span>15% for <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>44</mn></mrow></msub></math></span>), elastic constants increase with temperature due to local structural rearrangements and densification effects, while at higher Na<sub>2</sub>O content, they decrease because of thermal softening driven by enhanced Na<span><math><msup><mrow></mrow><mrow><mo>+</mo></mrow></msup></math></span> mobility and disruption of the silicate network. MD simulations confirm these trends with Na<sub>2</sub>O content and the same trends at high Na<sub>2</sub>O with temperature. However, at low Na<sub>2</sub>O, the elastic constants decrease slightly with temperature. Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio are determined from <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>11</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>44</mn></mrow></msub></math></span>. Novel metrics related to oxygen types and <span><math><msub><mrow><mi>Q<","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"301 ","pages":"Article 121565"},"PeriodicalIF":9.3,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145140719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of the influence of manganese on the dynamic strain ageing of ferritic steels – Part II: Industrial alloy","authors":"W. Mottay ,&nbsp;D. Caillard ,&nbsp;H. Idrissi ,&nbsp;P. Maugis ,&nbsp;A. Portavoce ,&nbsp;F. Roch ,&nbsp;C. Perrin-Pellegrino ,&nbsp;K. Hoummada","doi":"10.1016/j.actamat.2025.121576","DOIUrl":"10.1016/j.actamat.2025.121576","url":null,"abstract":"<div><div>Dynamic strain aging (DSA) was studied in an as-welded C-Mn steel at multiple scales, using macroscopic tensile tests, <em>in-situ</em> TEM tensile tests and atom probe tomography (APT). At the macroscopic scale, DSA is related to an increase in Ultimate Tensile Strength (UTS) between 423 K and 623 K, compared to room temperature. PLC serrations are observed in a limited temperature range, 423 K and 473 K. At the nano-scale, DSA manifests as a change in dislocation dynamics, namely the occurrence of dislocation bursts. Interestingly, high-temperature diffusion-controlled (HTDC) Peierls glide suppresses PLC serrations, and its velocity controls the end of DSA. Moreover, the occurrence of HTDC-Peierls glide suggests that interstitial atoms control DSA in the C-Mn weld, that being confirmed by the extracted activation energy for HTDC-Peierls glide and by APT characterizations showing the absence of Mn on dislocations. Contrary to what was observed in the Fe-3Mn-C model in the first part of this study, Mn does not influence DSA in this industrial C-Mn weld. We propose that the reduced Mn content does not lead to a sufficient anchoring of mixed dislocations, thus allowing for the occurrence of HTDC-Peierls glide. Consequently, screw dislocations, which do not attract Mn atoms, become prominent as deformation proceeds, therefore suppressing the Mn-controlled DSA. Based on these findings, we discuss previously published results regarding the manifestations of DSA in steels as a function of their chemical composition.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"301 ","pages":"Article 121576"},"PeriodicalIF":9.3,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145127856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Serrated grain boundary modulation inhibits nano cracks propagation in pure magnesium: A phase field crystal and quasi in-situ EBSD study","authors":"Huanqing Li ,&nbsp;Yuhong Zhao ,&nbsp;Zhuo Song ,&nbsp;Xiaolin Tian ,&nbsp;Ruifeng Dong ,&nbsp;Yuntao Zhang ,&nbsp;Hua Hou","doi":"10.1016/j.actamat.2025.121573","DOIUrl":"10.1016/j.actamat.2025.121573","url":null,"abstract":"<div><div>Modulating serrated grain boundaries (SGB) has the potential to enhance fracture properties in materials. This work investigates the crack behavior at SGB during loading through high-resolution transmission electron microscopy, quasi in-situ electron backscatter diffraction and phase field crystal simulations. Experimental results demonstrate that nano-crack initiation and propagation at SGBs driven by basal or prismatic &lt;a&gt; slip at varying angles between grains. Additionally, large shear strains are observed in the SGB bending regions, and portions of these regions that align with the loading direction impede crack propagation. Previous studies have suggested that a loading direction perpendicular to the grain boundary (GB) promotes intergranular fracture. However, our research demonstrates that the influence of the angle between GB and the loading direction on crack propagation is localized, with previous conclusions valid only within a strain range of 10-27%. Beyond this critical strain, cracks predominantly transgranular propagate in a brittle manner, with a weaker effect in the loading direction. Furthermore, when the angle between SGB and the loading direction is less than 65°, the proportion of the SGB parallel to the loading direction increases, thereby inhibiting intergranular fracture. Additionally, SGB curvature significantly impacts crack extension, with an optimal curvature of approximately 0.151 1/nm for double-serrated grain boundaries that effectively suppresses nano-crack propagation. The hindering effect of Lommer–Cottrell locks at the SGB bends on crack propagation is quantified by the geometric compatibility factor. This work may provide insights into enhancing material fracture strength through the control of SGB.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"301 ","pages":"Article 121573"},"PeriodicalIF":9.3,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145116205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Controlling magnetic interactions and domain dynamics in Co2NiO4 nanorods via carbon integrated structural modulation","authors":"Aslam Hossain ,&nbsp;Zhengyou Li ,&nbsp;Alexander V. Soldatov ,&nbsp;A.M.A. Henaish ,&nbsp;D.E. El Refaay ,&nbsp;Evgeniy Novikov","doi":"10.1016/j.actamat.2025.121575","DOIUrl":"10.1016/j.actamat.2025.121575","url":null,"abstract":"<div><div>Nanomaterials with tailored morphology, microstructure, and carbon integration exhibit profound impacts on their optical and magnetic properties. In this study, a series of carbon-integrated Co₂NiO₄ spinel nanorods were synthesized via a hydrothermal method by systematically varying co-precursor ratios, followed by post synthesis low-temperature air annealing. Elemental analysis and Rietveld-refined XRD patterns confirmed carbon incorporation within the spinel lattice, altering unit cell parameters and crystallite size. Electron microscopic study revealed uniform nanorod morphologies with density variations correlating to carbon content, while UV–Vis spectroscopy demonstrated tunable optical bandgaps (1.85–2.08 eV), attributed to carbon-induced mid-gap states and structural defects. Magnetic characterization revealed soft ferromagnetic behavior with systematic variations in coercivity, remanent magnetization, and saturation magnetization, driven by carbon-mediated defect engineering and Co/Ni stoichiometry. First-Order Reversal Curve (FORC) mapping further uncovered tunable interaction fields and coercivity distributions, highlighting the interplay of carbon-induced pinning effects and cation-driven superexchange interactions. The controlled synthesis and annealing process enabled precise modulation of morphology, carbon content, and cation distribution, offering a pathway to engineer multifunctional spinel oxides for advanced applications.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"301 ","pages":"Article 121575"},"PeriodicalIF":9.3,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145127416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A semi-analytic model of vacancy cluster thermodynamics with applications to transition metal carbides","authors":"Xiaochuan Tang ,&nbsp;Kaka Ma ,&nbsp;Gregory B. Thompson ,&nbsp;Christopher R. Weinberger","doi":"10.1016/j.actamat.2025.121574","DOIUrl":"10.1016/j.actamat.2025.121574","url":null,"abstract":"<div><div>Vacancies are well known to alter a wide range of material properties from electrical conductivity to creep rates. However, there is a dearth of understanding of how vacancy clustering occurs in compounds where vacancy clustering is significant which is highlighted in the B1 structure transition metal carbides. In this study, we present a semi-analytical model for vacancy cluster thermodynamics, which accounts for both isolated vacancies and vacancy clusters by minimizing the total Helmholtz free energy. This approach enables the prediction of equilibrium vacancy concentrations while incorporating configurational entropy and temperature-dependent formation energetics. The model is then applied to two B1-structured transition metal carbides, <span><math><mtext>TiC</mtext></math></span> and <span><math><mtext>TaC</mtext></math></span>, where the isolated vacancy formation energies and vacancy-cluster binding energies are determined using density functional theory (DFT) calculations. Contributions from vibrational and electronic entropies are also included, which highlights the different bonding in group IVB and VB monocarbides. The results suggest that metal vacancy concentration at thermodynamic equilibrium exhibits a non-Arrhenius behavior since vacancy-cluster formation not only changes the formation energy but also significantly lowers the configurational entropy. This means that the formation of metal vacancies depends on both the temperature and the carbon vacancy concentration, which provides insights into the self-diffusion mechanism in transition metal carbides. Furthermore, the theory presented here can be applied to a wide range of materials to understand the role vacancy clustering in compounds.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"301 ","pages":"Article 121574"},"PeriodicalIF":9.3,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145116204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atomic-scale cocoonlike interfacial segregation stabilizes the nanoprecipitates in a dilute Mg-Mn-Al-Ca-Ce alloy","authors":"Zhen-Ming Hua ,&nbsp;Shuai-Lei Wu ,&nbsp;Min Zha ,&nbsp;Yulong Zhu ,&nbsp;Zhangting Hu ,&nbsp;Peng Chen ,&nbsp;Xin-Yu Xu ,&nbsp;Shuang Li ,&nbsp;Cheng Wang ,&nbsp;Shen-Bao Jin ,&nbsp;Upadrasta Ramamurty ,&nbsp;Hui-Yuan Wang","doi":"10.1016/j.actamat.2025.121572","DOIUrl":"10.1016/j.actamat.2025.121572","url":null,"abstract":"<div><div>Achieving densely distributed and thermally stable nanoprecipitates is critical in the development of Mg alloys suitable for long-time thermal exposure at elevated temperatures. Herein, highly stable β-Mn nanoprecipitates with a high volumetric number density (∼1.1 × 10²⁰ m^-3) are created in a dilute Mg-0.6Mn-0.5Al-0.2Ca-0.3Ce (wt.%) alloy, which stem from the formation of a unique core-shell structure characterized by a Ca-Ce cocoonlike segregation layer. Through detailed multi-scale characterizations and Molecular Dynamics/Monte Carlo simulations, we reveal that the segregation layer forms through a complex dynamic solute repartitioning behavior, wherein Ca and Ce, attracted into the β-Mn nanoprecipitates during hot rolling at 598 K, are repelled toward precipitate interface upon subsequent thermal exposure at 753 K. This process is driven by the changes in the local strain fields that arise from the increased Mn/Al ratio in the β-Mn nanoprecipitates. These core-shell β-Mn nanoprecipitates effectively stabilize the fine-grained structure (∼13-16 μm), with negligible degradation of yield strength when extending exposure time from 10 min to 3000 min at 753 K, <em>i.e.</em>, ∼82% of the melting point of pure Mg. Our work illustrates how solute atoms with large differences in diffusivities can work synergistically to form densely distributed and highly stable nanoprecipitates even in a dilute Mg alloy, and the results could provide new insights into the development of high-performance alloys with superior microstructure stability.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"301 ","pages":"Article 121572"},"PeriodicalIF":9.3,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145116248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation mechanism of polar nanoregion in heterovalent doped incipient ferroelectrics","authors":"Dongxiao Fan ,&nbsp;Cong Lu","doi":"10.1016/j.actamat.2025.121558","DOIUrl":"10.1016/j.actamat.2025.121558","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Incipient ferroelectric SrTiO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; is known as the structural competition between the ferroelectric polar displacement of Ti ion and antiferrodistortive (AFD) rotation of TiO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; octahedron. Pr-doped SrTiO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; (SPTO) possesses relaxor-type ferroelectricity and exhibits both enhanced ferroelectric polar and antiferrodistortion. Here, we use double-edge X-ray absorption spectroscopy fine structure (XAFS: XANES &amp; EXAFS) to investigate the local structure of the SPTO relaxor and the co-existing nature of these two structural distortions. The enhanced local polar is observed by the increment of the A&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; peak of Ti &lt;span&gt;&lt;math&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;-edge XANES spectra, whose intensity is proportional to the displacement value of the Ti ion. The exact value of Ti displacement is obtained by geometrical analysis of the Ti &lt;span&gt;&lt;math&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;-edge EXAFS spectra. Sr &lt;span&gt;&lt;math&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;-edge EXAFS results show the angle of the AFD rotation of TiO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; octahedron is also increased with Pr doping. With the help of the &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;b&lt;/mi&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;mi&gt;t&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;mi&gt;o&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; calculation, the existence of V&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;Sr&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;, which is produced by charge compensation after the substitution of Pr&lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; on the Sr&lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; site (Pr&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;Sr&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;•&lt;/mo&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;), is confirmed by the decreased A&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; peak of Ti &lt;span&gt;&lt;math&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;-edge XANES. These results explain that the simultaneous enhancement of the ferroelectric polar and the antiferrodistortion in the SPTO relaxor originates from the co-work of the point defects of Pr&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;Sr&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;•&lt;/mo&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; and V&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;Sr&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;. Based on our results, a structural mechanism of the PNR formation in the SPTO relaxor is proposed. This study elucidates the mechanism of the heterovalent doping-induced relaxor property in SrTiO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and paves the way to induce relaxor property in other incipient ferroelec","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"301 ","pages":"Article 121558"},"PeriodicalIF":9.3,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145116206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atomistic mechanisms of oxidation and chlorine corrosion in Ni-based superalloys: The role of boron and light interstitial segregation","authors":"Tyler D. Doležal ,&nbsp;Rodrigo Freitas ,&nbsp;Ju Li","doi":"10.1016/j.actamat.2025.121556","DOIUrl":"10.1016/j.actamat.2025.121556","url":null,"abstract":"<div><div>Hybrid Monte Carlo and molecular dynamics simulations were used to investigate the interaction of light interstitials in multi-element Ni-based alloys. We show that light interstitials such as boron and oxygen fundamentally alter interfacial chemistry by reshaping alloy-element distribution and segregation. Oxygen adsorption drove boron migration from the grain boundary to the free surface, where it co-enriched with Cr, Fe, and Mo and formed BO3 trigonal motifs embedded within mixed-metal oxide networks. Oxygen also promoted M<img>O<img>M chain formation, including Nb2O5 clusters at the free surface. In the absence of oxygen, boron segregated to the grain boundary, altering local metal chemistry and underscoring a dynamic, environment-sensitive behavior. Following chlorine exposure, the oxidized surfaces retained strong O-mediated connectivity while forming new Cl<img>M associations, particularly with Nb and Cr, and exhibited further surface enrichment in Cr, Fe, and Mo. High-temperature MD simulations revealed a dynamic tug-of-war: chlorine exerted upward pull and disrupted weakly anchored sites, while Nb- and BO3-rich oxide motifs resisted deformation. A new stabilization mechanism was identified in which subsurface boron atoms anchored overlying Cr centers, suppressing their mobility and mitigating chlorine-driven displacement. These results demonstrate boron’s dual role as a modifier of alloy-element segregation and a stabilizer of oxide networks, and identify Nb as a key element in reinforcing cohesion under halogen attack. More broadly, this study highlights the need to track light interstitial cross-talk and solute migration under reactive conditions, offering atomistic criteria for designing corrosion-resistant surface chemistries in Ni-based superalloys exposed to halogenated or oxidative environments.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"301 ","pages":"Article 121556"},"PeriodicalIF":9.3,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145103767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anomalous temperature effects on the twinning-dislocation transition in magnesium: in-situ quantitative thermal-mechanical investigations","authors":"Fei Liu ,&nbsp;Bo-Yu Liu ,&nbsp;Yu-Han Tian ,&nbsp;Si-Yuan Wei ,&nbsp;Song Xiang ,&nbsp;Upadrasta Ramamurty ,&nbsp;Zhi-Wei Shan","doi":"10.1016/j.actamat.2025.121571","DOIUrl":"10.1016/j.actamat.2025.121571","url":null,"abstract":"<div><div>The effect of temperature on the plastic deformation mechanisms in submicron magnesium (Mg) single crystal is investigated by performing <em>in-situ</em> mechanical tests inside transmission electron microscope over the temperature range of 25 and 300 °C. The deformation in submicron Mg under compression along <span><math><mrow><mo>[</mo><mrow><mn>01</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>0</mn></mrow><mo>]</mo></mrow></math></span> orientation transitions from twinning- to dislocation-dominated one over the temperature range of 210-250 °C. Below this temperature range, deformation is governed by <span><math><mrow><mo>{</mo><mrow><mn>10</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo></mrow></math></span> deformation twins, while it is dominated by non-basal 〈a〉 dislocation slip above it. Under tension along [0001], due to the higher critical resolved shear stress (CRSS) for the pyramidal 〈c+a〉 dislocation slip (compared to that of <span><math><mrow><mo>{</mo><mrow><mn>10</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo></mrow></math></span> deformation twins), no transition involving twins and pyramidal 〈c+a〉 dislocation slip occurs over the tested temperature range. Interestingly, an abnormal increase in the CRSS of <span><math><mrow><mo>{</mo><mrow><mn>10</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo></mrow></math></span> deformation twinning with the temperature is observed, both under compression and tension. Critical experiments show that the observed anomalous temperature dependence is not caused by the stress required for twin boundary migration, which remains invariant with temperature, but may be attributed to the lack of heterogenous nucleation sites for twin nucleation at high temperatures. These findings provide new insights into the transition from twinning- to dislocation-dominated plasticity in Mg and its alloys at elevated temperatures. The methodology can be extended to investigate the high-temperature deformation behavior and mechanisms in other materials.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"301 ","pages":"Article 121571"},"PeriodicalIF":9.3,"publicationDate":"2025-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145093669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In situ observation of phase transitions in La2NiO4+δ bulk and thin film samples via Raman spectroscopy","authors":"Adeel Riaz ,&nbsp;Alexander Stangl ,&nbsp;Mónica Burriel ,&nbsp;Michel Mermoux","doi":"10.1016/j.actamat.2025.121570","DOIUrl":"10.1016/j.actamat.2025.121570","url":null,"abstract":"<div><div>La₂NiO_4+δ has attracted increasing interest in recent years, both as oxygen electrode in solid oxide fuel cells and electrolysers due to its high electrochemical activity at intermediate-to-low temperatures, and as key component of memristive devices for neuromorphic computing, owing to its variable oxygen stoichiometry. The integration of La₂NiO_4+δ into devices operating at different temperatures and oxygen partial pressures requires knowledge of the effects of hyper-stoichiometry (δ) on its crystalline structure. La₂NiO_4+δ is known to accommodate oxygen at interstitial sites allowing for large δ values, up to ∼ 0.16. In addition, the O-doping - temperature phase diagram is known to be complex, exhibiting several phase transitions with increasing δ. Herein, we use Raman spectroscopy to monitor the effects of O-doping in the phase diagram and the various structures it contains. Throughout this work, we studied this material in its usual ceramic form, as well as in the form of thin films. Results are discussed in terms of phase transitions, chemical expansion, and some of the possible consequences of the low mean grain size inherent to such thin films.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"301 ","pages":"Article 121570"},"PeriodicalIF":9.3,"publicationDate":"2025-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145093670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}