Pub Date : 2026-01-09DOI: 10.1016/j.actamat.2026.121919
Zhe Li , Liang Wang , Baoxian Su , Qingda Zhang , Jiaxin Du , Zhiwen Li , Chen Liu , Ruirun Chen , Daniel Şopu , Parthiban Ramasamy , Jürgen Eckert , Yanqing Su
The synergistic enhancement of strength and ductility remains an urgently demanded challenge for refractory high entropy alloys (RHEAs). Here, we propose a novel preexisting twinning strategy to achieve excellent strength-ductility synergy. Advanced crystallographic analysis and molecular dynamics simulations reveal that the mechanism of preexisting {112}<111> twinning enhances the ductility via inducing rotational twinning. The rotational twins serve as an effective slip transfer interface and dislocation reaction node, which facilitates the local strain coordination. More crucially, the following rotational twin modes have been identified: {}<>, {}<>, {}<>, {}<> (rotation around the common <110> pole), and a special {}<111> mode, in stark contrast to the classical twinning shear mechanism. At 723-823 K, preexisting twins trigger early dynamic recrystallization, refine grain structures, and serve as nucleation sites for deformation twins, while atomic kinks along the rotational twin boundaries dynamically drive twin rotation and suppress crack propagation. Consequently, the non-equiatomic TiNbZrHfTa alloy reaches a remarkable yield strength of ∼660±11 MPa with 20.74±1.26% elongation at 723 K, and elongations exceeding 17% at 823 K and 50% at 923 K, respectively, which successfully overcomes the intermediate-to-high-temperature embrittlement problem of RHEAs. Altogether, this work offers a transformative pathway for designing high-performance RHEAs for extreme environments.
{"title":"Unveiling superior ductility in refractory high entropy alloy through preexisting {112}<111> twins and novel rotational twinning dynamics","authors":"Zhe Li , Liang Wang , Baoxian Su , Qingda Zhang , Jiaxin Du , Zhiwen Li , Chen Liu , Ruirun Chen , Daniel Şopu , Parthiban Ramasamy , Jürgen Eckert , Yanqing Su","doi":"10.1016/j.actamat.2026.121919","DOIUrl":"10.1016/j.actamat.2026.121919","url":null,"abstract":"<div><div>The synergistic enhancement of strength and ductility remains an urgently demanded challenge for refractory high entropy alloys (RHEAs). Here, we propose a novel preexisting twinning strategy to achieve excellent strength-ductility synergy. Advanced crystallographic analysis and molecular dynamics simulations reveal that the mechanism of preexisting {112}<111> twinning enhances the ductility via inducing rotational twinning. The rotational twins serve as an effective slip transfer interface and dislocation reaction node, which facilitates the local strain coordination. More crucially, the following rotational twin modes have been identified: {<span><math><mrow><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>4</mn></mrow></math></span>}<<span><math><mrow><mn>2</mn><mover><mrow><mn>21</mn></mrow><mo>‾</mo></mover></mrow></math></span>>, {<span><math><mrow><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>5</mn></mrow></math></span>}<<span><math><mrow><mn>5</mn><mover><mrow><mn>52</mn></mrow><mo>‾</mo></mover></mrow></math></span>>, {<span><math><mrow><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>7</mn></mrow></math></span>}<<span><math><mrow><mn>7</mn><mover><mrow><mn>72</mn></mrow><mo>‾</mo></mover></mrow></math></span>>, {<span><math><mrow><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>9</mn></mrow></math></span>}<<span><math><mrow><mn>9</mn><mover><mrow><mn>92</mn></mrow><mo>‾</mo></mover></mrow></math></span>> (rotation around the common <110> pole), and a special {<span><math><mrow><mover><mrow><mn>21</mn></mrow><mo>‾</mo></mover><mn>1</mn></mrow></math></span>}<111> mode, in stark contrast to the classical twinning shear mechanism. At 723-823 K, preexisting twins trigger early dynamic recrystallization, refine grain structures, and serve as nucleation sites for deformation twins, while atomic kinks along the rotational twin boundaries dynamically drive twin rotation and suppress crack propagation. Consequently, the non-equiatomic TiNbZrHfTa alloy reaches a remarkable yield strength of ∼660±11 MPa with 20.74±1.26% elongation at 723 K, and elongations exceeding 17% at 823 K and 50% at 923 K, respectively, which successfully overcomes the intermediate-to-high-temperature embrittlement problem of RHEAs. Altogether, this work offers a transformative pathway for designing high-performance RHEAs for extreme environments.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"306 ","pages":"Article 121919"},"PeriodicalIF":9.3,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974296","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}
Pub Date : 2026-01-09DOI: 10.1016/j.actamat.2026.121920
Haoyu Zhai , Han Chen , Hao Lin , Yuchi Cui , Junjie Yang , Xiaoqing Shang , Jiachen Long , Pucong Sheng , Shengyi Zhong
Hydride precipitation and spatial morphology critically influence the mechanical degradation of zirconium (Zr) alloys and, consequently, the service life of nuclear fuel cladding. While numerous studies have demonstrated that the stress state affects hydride precipitation and morphology, most focus on macroscale external stresses, with limited attention to the role of internal stresses. In this study, we investigate the mechanistically unresolved influence of intergranular internal stress on hydride precipitation and morphology in Zr-2.5Nb pressure tube alloys using texture-component-dependent neutron diffraction method. Our results reveal that intergranular internal stress in this Zr alloy strongly depends on grain orientation. In particular, grains with basal planes oriented at 45–90° relative to the radial direction experience very high tensile internal stress. This elevated internal stress promotes hydride precipitation and facilitates the formation of circumferential hydrides with larger-scale features by lowering the nucleation energy in these grains. Conversely, when internal stress is significantly reduced, preferential nucleation is suppressed, leading to a more uniform distribution of circumferential and radial hydrides with finer and more discrete features. This study highlights the critical role of orientation-dependent internal stress in directing hydride precipitation and morphology through preferential nucleation mechanism. These findings offer valuable guidance for residual stress engineering aimed at optimizing hydride morphology, enhancing cladding integrity, and informing improved materials design for nuclear systems.
{"title":"Orientation-dependent intergranular internal stress in Zr-2.5Nb alloys: Implications for hydride precipitation and morphology","authors":"Haoyu Zhai , Han Chen , Hao Lin , Yuchi Cui , Junjie Yang , Xiaoqing Shang , Jiachen Long , Pucong Sheng , Shengyi Zhong","doi":"10.1016/j.actamat.2026.121920","DOIUrl":"10.1016/j.actamat.2026.121920","url":null,"abstract":"<div><div>Hydride precipitation and spatial morphology critically influence the mechanical degradation of zirconium (Zr) alloys and, consequently, the service life of nuclear fuel cladding. While numerous studies have demonstrated that the stress state affects hydride precipitation and morphology, most focus on macroscale external stresses, with limited attention to the role of internal stresses. In this study, we investigate the mechanistically unresolved influence of intergranular internal stress on hydride precipitation and morphology in Zr-2.5Nb pressure tube alloys using texture-component-dependent neutron diffraction method. Our results reveal that intergranular internal stress in this Zr alloy strongly depends on grain orientation. In particular, grains with basal planes oriented at 45–90° relative to the radial direction experience very high tensile internal stress. This elevated internal stress promotes hydride precipitation and facilitates the formation of circumferential hydrides with larger-scale features by lowering the nucleation energy in these grains. Conversely, when internal stress is significantly reduced, preferential nucleation is suppressed, leading to a more uniform distribution of circumferential and radial hydrides with finer and more discrete features. This study highlights the critical role of orientation-dependent internal stress in directing hydride precipitation and morphology through preferential nucleation mechanism. These findings offer valuable guidance for residual stress engineering aimed at optimizing hydride morphology, enhancing cladding integrity, and informing improved materials design for nuclear systems.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"306 ","pages":"Article 121920"},"PeriodicalIF":9.3,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035072","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}
Pub Date : 2026-01-08DOI: 10.1016/j.actamat.2026.121902
Mohammad Ali Seyed Mahmoud , Dominic Renner , Ali Khosravani , Surya R. Kalidindi
Reliable parameter identification in ductile damage models remains challenging because the salient physics of damage progression are localized to small regions in material responses, and their signatures are often diluted in specimen-level measurements. Here, we propose a sequential Bayesian Inference (BI) framework for the calibration of the Gurson–Tvergaard–Needleman (GTN) model using multimodal experimental data (i.e., the specimen-level force–displacement (F–D) measurements and the spatially resolved digital image correlation (DIC) strain fields). This calibration approach builds on a previously developed two-step BI framework that first establishes a low-computational-cost emulator for a physics-based simulator (here, a finite element model incorporating the GTN material model) and then uses the experimental data to sample posteriors for the material model parameters using the Transitional Markov Chain Monte Carlo (T-MCMC). A central challenge to the successful application of this BI framework to the present problem arises from the high-dimensional representations needed to capture the salient features embedded in the F–D curves and the DIC fields. In this paper, it is demonstrated that Principal Component Analysis (PCA) provides low-dimensional representations that make it possible to apply the BI framework to the problem. Most importantly, it is shown that the sequence in which the BI is applied has a dramatic influence on the results obtained. Specifically, it is observed that applying BI first on F–D curves and subsequently on the DIC fields produces improved estimates of the GTN parameters. Possible causes for these observations are discussed in this paper, using AA6111 aluminum alloy as a case study.
{"title":"Sequential Bayesian Inference of the GTN damage model using multimodal experimental data","authors":"Mohammad Ali Seyed Mahmoud , Dominic Renner , Ali Khosravani , Surya R. Kalidindi","doi":"10.1016/j.actamat.2026.121902","DOIUrl":"10.1016/j.actamat.2026.121902","url":null,"abstract":"<div><div>Reliable parameter identification in ductile damage models remains challenging because the salient physics of damage progression are localized to small regions in material responses, and their signatures are often diluted in specimen-level measurements. Here, we propose a sequential Bayesian Inference (BI) framework for the calibration of the Gurson–Tvergaard–Needleman (GTN) model using multimodal experimental data (i.e., the specimen-level force–displacement (F–D) measurements and the spatially resolved digital image correlation (DIC) strain fields). This calibration approach builds on a previously developed two-step BI framework that first establishes a low-computational-cost emulator for a physics-based simulator (here, a finite element model incorporating the GTN material model) and then uses the experimental data to sample posteriors for the material model parameters using the Transitional Markov Chain Monte Carlo (T-MCMC). A central challenge to the successful application of this BI framework to the present problem arises from the high-dimensional representations needed to capture the salient features embedded in the F–D curves and the DIC fields. In this paper, it is demonstrated that Principal Component Analysis (PCA) provides low-dimensional representations that make it possible to apply the BI framework to the problem. Most importantly, it is shown that the sequence in which the BI is applied has a dramatic influence on the results obtained. Specifically, it is observed that applying BI first on F–D curves and subsequently on the DIC fields produces improved estimates of the GTN parameters. Possible causes for these observations are discussed in this paper, using AA6111 aluminum alloy as a case study.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"306 ","pages":"Article 121902"},"PeriodicalIF":9.3,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923458","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}
Pub Date : 2026-01-08DOI: 10.1016/j.actamat.2026.121895
Ertugrul Demir , Saikumaran Ayyapan , Weiyue Zhou , Wande Cairang , Kevin B. Woller , Michael P. Short , Djamel Kaoumi
{"title":"Corrigendum to 'Behavior of Fe-based alloys in a liquid lead-bismuth environment under simultaneous proton irradiation and corrosion'","authors":"Ertugrul Demir , Saikumaran Ayyapan , Weiyue Zhou , Wande Cairang , Kevin B. Woller , Michael P. Short , Djamel Kaoumi","doi":"10.1016/j.actamat.2026.121895","DOIUrl":"10.1016/j.actamat.2026.121895","url":null,"abstract":"","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"305 ","pages":"Article 121895"},"PeriodicalIF":9.3,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145972934","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}
Pub Date : 2026-01-07DOI: 10.1016/j.actamat.2026.121907
Xin Wang , Xusheng Yang , Weijiu Huang , Yunchang Xin , Dehong Lu , Xianghui Zhu , Mengdi Li , Yanzheng Guo
The plate–shaped T1 phase serves as the primary strengthening precipitate in the advanced Al–Li alloys, and its spatial distribution is a critical factor affecting alloy performance. In this study, electron backscatter diffraction (EBSD), focused ion beam (FIB), and transmission electron microscopy (TEM) were combined to investigate the spatial distribution of T1 plates in specific crystal orientations. The results revealed that the preferred T1 variants mostly precipitated on the habit plane with the maximum Schmid factor. A modified strengthening model was developed considering the uneven distribution of T1 phase. To verify the accuracy of this model, yield strength tests were performed on a single grain using nanoindentation. The analysis indicated that precipitation strengthening could be substantially overestimated in grains containing preferential T1 variants. This study provides a quantitative and precise evaluation of precipitation strengthening in Al–Cu–Li–Mg–Ag alloys, considering specific crystal orientation and spatial distribution.
{"title":"Quantitative study of precipitation strengthening effects of T1 phase in Al–Cu–Li–Mg–Ag alloy: Role of nonuniform spatial distribution","authors":"Xin Wang , Xusheng Yang , Weijiu Huang , Yunchang Xin , Dehong Lu , Xianghui Zhu , Mengdi Li , Yanzheng Guo","doi":"10.1016/j.actamat.2026.121907","DOIUrl":"10.1016/j.actamat.2026.121907","url":null,"abstract":"<div><div>The plate–shaped T<sub>1</sub> phase serves as the primary strengthening precipitate in the advanced Al–Li alloys, and its spatial distribution is a critical factor affecting alloy performance. In this study, electron backscatter diffraction (EBSD), focused ion beam (FIB), and transmission electron microscopy (TEM) were combined to investigate the spatial distribution of T<sub>1</sub> plates in specific crystal orientations. The results revealed that the preferred T<sub>1</sub> variants mostly precipitated on the habit plane with the maximum Schmid factor. A modified strengthening model was developed considering the uneven distribution of T<sub>1</sub> phase. To verify the accuracy of this model, yield strength tests were performed on a single grain using nanoindentation. The analysis indicated that precipitation strengthening could be substantially overestimated in grains containing preferential T<sub>1</sub> variants. This study provides a quantitative and precise evaluation of precipitation strengthening in Al–Cu–Li–Mg–Ag alloys, considering specific crystal orientation and spatial distribution.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"306 ","pages":"Article 121907"},"PeriodicalIF":9.3,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145919763","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}
Pub Date : 2026-01-07DOI: 10.1016/j.actamat.2025.121891
J.P. Magnussen , Í. Carneiro , K. Ma , C. Coleman , A. Wisbey , H. Swan , A.J. Knowles
The use of conventional zirconium alloys at temperatures above 400 °C is limited by high temperature strength and creep resistance. This has prevented the consideration of zirconium alloys for fusion and Generation IV fission plant designs operating at 500 °C–1000 °C. The physical metallurgy of zirconium is similar to titanium which has seen alloying advances allowing application temperatures up to 600 °C. Although the oxidation resistance of zirconium-based alloys is expected to be poor, in a water environment, new Generation-IV and fusion reactors are designed to operate using alternative coolants such as liquid metals and molten salts. Therefore, a new class of zirconium alloys in the Zr-Al-Sn-(Si,Cr,V) system, designed by analogy to near- titanium alloys, were synthesised by arc melting and processed in a sequence of homogenisation, hot/cold rolling, recrystallisation, and ageing treatments. Microscopy and diffraction identified a refined fully lath grain structure reinforced by nanoscale lamellar or discrete coherent Zr3Al precipitates, with morphology and crystal structure differing with ageing times. Additionally alloying with Si, Cr, and V respectively leads to Zr2Si, ZrCr2, and ZrV2 incoherent precipitates. Tensile testing revealed a strengthening effect by Al, but with significant changes to ductility on ageing depending on the evolution of Zr3Al. Creep testing showed creep rates orders of magnitude better than conventional Zircaloy-4 and nuclear ferritic/martensitic steels, approaching near- Ti alloys. The present work offers new insights and perspectives into how high-temperature zirconium alloys might be designed to meet the requirements for fusion and Gen-IV fission.
{"title":"High temperature zirconium alloys Zr-Al-Sn-(Si,Cr,V) by near-α titanium analogy","authors":"J.P. Magnussen , Í. Carneiro , K. Ma , C. Coleman , A. Wisbey , H. Swan , A.J. Knowles","doi":"10.1016/j.actamat.2025.121891","DOIUrl":"10.1016/j.actamat.2025.121891","url":null,"abstract":"<div><div>The use of conventional zirconium alloys at temperatures above 400 °C is limited by high temperature strength and creep resistance. This has prevented the consideration of zirconium alloys for fusion and Generation IV fission plant designs operating at 500 °C–1000 °C. The physical metallurgy of zirconium is similar to titanium which has seen alloying advances allowing application temperatures up to 600 °C. Although the oxidation resistance of zirconium-based alloys is expected to be poor, in a water environment, new Generation-IV and fusion reactors are designed to operate using alternative coolants such as liquid metals and molten salts. Therefore, a new class of zirconium alloys in the Zr-Al-Sn-(Si,Cr,V) system, designed by analogy to near-<span><math><mi>α</mi></math></span> titanium alloys, were synthesised by arc melting and processed in a sequence of homogenisation, hot/cold rolling, recrystallisation, and ageing treatments. Microscopy and diffraction identified a refined fully lath grain structure reinforced by nanoscale lamellar or discrete coherent Zr<sub>3</sub>Al precipitates, with morphology and crystal structure differing with ageing times. Additionally alloying with Si, Cr, and V respectively leads to Zr<sub>2</sub>Si, ZrCr<sub>2</sub>, and ZrV<sub>2</sub> incoherent precipitates. Tensile testing revealed a strengthening effect by Al, but with significant changes to ductility on ageing depending on the evolution of Zr<sub>3</sub>Al. Creep testing showed creep rates orders of magnitude better than conventional Zircaloy-4 and nuclear ferritic/martensitic steels, approaching near-<span><math><mi>α</mi></math></span> Ti alloys. The present work offers new insights and perspectives into how high-temperature zirconium alloys might be designed to meet the requirements for fusion and Gen-IV fission.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"306 ","pages":"Article 121891"},"PeriodicalIF":9.3,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145919766","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}
Pub Date : 2026-01-06DOI: 10.1016/j.actamat.2026.121906
Nikita Polin , Shangbin Shen , Fernando Maccari , Alex Aubert , Esmaeil Adabifiroozjaei , Tatiana Smoliarova , Yangyiwei Yang , Xinren Chen , Yurii Skourski , Alaukik Saxena , András Kovács , Rafal E. Dunin-Borkowski , Michael Farle , Bai-Xiang Xu , Leopoldo Molina-Luna , Oliver Gutfleisch , Baptiste Gault , Konstantin Skokov
Permanent magnets containing rare earth elements are essential components for the electrification of society. Ce(Co1-xCux)5 permanent magnets are a model system known for their substantial coercivity, yet the underlying mechanism remains unclear. Here, we investigate Ce(Co0.8Cu0.2)5.4 magnets with a coercivity of ∼1 T. Using transmission electron microscopy (TEM) and atom probe tomography (APT), we identify a nanoscale cellular structure formed by spinodal decomposition. Cu-poor cylindrical cells (∼5–10 nm in diameter, ∼20 nm long) have a disordered CeCo5-type structure and a composition Ce(Co0.9Cu0.1)5.3. Cu-rich cell boundaries are ∼ 5 nm thick and exhibit a modified CeCo5 structure, with Cu ordered on the Co sites and a composition Ce(Co0.7Cu0.3)5.0. Micromagnetic simulations demonstrate that the intrinsic Cu concentration gradients up to 12 at.% Cu/nm lead to a spatial variation in magnetocrystalline anisotropy and domain wall energy, resulting in effective pinning and high coercivity. Compared to Sm2Co17-type magnets, Ce(Co0.8Cu0.2)5.4 displays a finer-scale variation of conventional pinning with lower structural and chemical contrast in its underlying nanostructure. The identification of nanoscale chemical segregation in nearly single-phase Ce(Co0.8Cu0.2)5.4 magnets provides a microstructural basis for the long-standing phenomenon of "giant intrinsic magnetic hardness" in systems such as SmCo5-xMx, highlighting avenues for designing rare-earth-lean permanent magnets via controlled nanoscale segregation.
{"title":"Direct observation of nanoscale pinning centers in Ce(Co0.8Cu0.2)5.4 permanent magnets","authors":"Nikita Polin , Shangbin Shen , Fernando Maccari , Alex Aubert , Esmaeil Adabifiroozjaei , Tatiana Smoliarova , Yangyiwei Yang , Xinren Chen , Yurii Skourski , Alaukik Saxena , András Kovács , Rafal E. Dunin-Borkowski , Michael Farle , Bai-Xiang Xu , Leopoldo Molina-Luna , Oliver Gutfleisch , Baptiste Gault , Konstantin Skokov","doi":"10.1016/j.actamat.2026.121906","DOIUrl":"10.1016/j.actamat.2026.121906","url":null,"abstract":"<div><div>Permanent magnets containing rare earth elements are essential components for the electrification of society. Ce(Co<sub>1-x</sub>Cu<sub>x</sub>)<sub>5</sub> permanent magnets are a model system known for their substantial coercivity, yet the underlying mechanism remains unclear. Here, we investigate Ce(Co<sub>0.8</sub>Cu<sub>0.2</sub>)<sub>5.4</sub> magnets with a coercivity of ∼1 T. Using transmission electron microscopy (TEM) and atom probe tomography (APT), we identify a nanoscale cellular structure formed by spinodal decomposition. Cu-poor cylindrical cells (∼5–10 nm in diameter, ∼20 nm long) have a disordered CeCo<sub>5</sub>-type structure and a composition Ce(Co<sub>0.9</sub>Cu<sub>0.1</sub>)<sub>5.3</sub>. Cu-rich cell boundaries are ∼ 5 nm thick and exhibit a modified CeCo<sub>5</sub> structure, with Cu ordered on the Co sites and a composition Ce(Co<sub>0.7</sub>Cu<sub>0.3</sub>)<sub>5.0</sub>. Micromagnetic simulations demonstrate that the intrinsic Cu concentration gradients up to 12 at.% Cu/nm lead to a spatial variation in magnetocrystalline anisotropy and domain wall energy, resulting in effective pinning and high coercivity. Compared to Sm<sub>2</sub>Co<sub>17</sub>-type magnets, Ce(Co<sub>0.8</sub>Cu<sub>0.2</sub>)<sub>5.4</sub> displays a finer-scale variation of conventional pinning with lower structural and chemical contrast in its underlying nanostructure. The identification of nanoscale chemical segregation in nearly single-phase Ce(Co<sub>0.8</sub>Cu<sub>0.2</sub>)<sub>5.4</sub> magnets provides a microstructural basis for the long-standing phenomenon of \"giant intrinsic magnetic hardness\" in systems such as SmCo<sub>5-x</sub>M<sub>x</sub>, highlighting avenues for designing rare-earth-lean permanent magnets via controlled nanoscale segregation.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"307 ","pages":"Article 121906"},"PeriodicalIF":9.3,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145919764","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}
Pub Date : 2026-01-06DOI: 10.1016/j.actamat.2025.121890
Mohammad Hadi Yazdani , Aoyan Liang , Ashley J. Maldonado Otero , Yi Liu , Diana Farkas , Andrea M. Hodge , Timothy J. Rupert , Irene J. Beyerlein , Paulo S. Branicio
In this study, molecular dynamics (MD) simulations are combined with magnetron co-sputtering experiments to examine how Ni-Fe and Ni-Cr compositions affect defect energetics and twin microstructure in thin films. These simulations represent the first direct modeling of nanotwin formation during atomistic thin film deposition. Ensemble MD simulations reveal substantial stochastic variability in grain structure and twin development across deposition runs, yet clear compositional trends emerge. Cr-rich Ni-Cr alloys form dense twin networks with narrow spacing, while Fe-rich Ni-Fe alloys exhibit fewer twins with significantly larger spacing. Scanning transmission electron microscopy (STEM) of Ni-Cr films confirms the predicted high twin density and reduced spacing, validating the link between alloy composition and growth twin formation. Notably, both simulations and experiments reveal that the distribution of twin boundary spacings is log-normal, reflecting the stochastic nature of twin nucleation during deposition. Composition-dependent maps from MD simulations further demonstrate that small variations in Ni-Cr and Ni-Fe chemistry can systematically tune twin boundary formation and enable the design of nanoscale twin architectures. This integrated computational-experimental study establishes a clear inverse relationship between stacking fault energy and average twin spacing, offering a pathway for engineering nanostructured coatings with tailored twin networks and enhanced properties.
{"title":"Composition-driven nanotwin engineering in sputtered Ni-Fe and Ni-Cr films: linking fault energetics to twin thickness","authors":"Mohammad Hadi Yazdani , Aoyan Liang , Ashley J. Maldonado Otero , Yi Liu , Diana Farkas , Andrea M. Hodge , Timothy J. Rupert , Irene J. Beyerlein , Paulo S. Branicio","doi":"10.1016/j.actamat.2025.121890","DOIUrl":"10.1016/j.actamat.2025.121890","url":null,"abstract":"<div><div>In this study, molecular dynamics (MD) simulations are combined with magnetron co-sputtering experiments to examine how Ni-Fe and Ni-Cr compositions affect defect energetics and twin microstructure in thin films. These simulations represent the first direct modeling of nanotwin formation during atomistic thin film deposition. Ensemble MD simulations reveal substantial stochastic variability in grain structure and twin development across deposition runs, yet clear compositional trends emerge. Cr-rich Ni-Cr alloys form dense twin networks with narrow spacing, while Fe-rich Ni-Fe alloys exhibit fewer twins with significantly larger spacing. Scanning transmission electron microscopy (STEM) of Ni-Cr films confirms the predicted high twin density and reduced spacing, validating the link between alloy composition and growth twin formation. Notably, both simulations and experiments reveal that the distribution of twin boundary spacings is log-normal, reflecting the stochastic nature of twin nucleation during deposition. Composition-dependent maps from MD simulations further demonstrate that small variations in Ni-Cr and Ni-Fe chemistry can systematically tune twin boundary formation and enable the design of nanoscale twin architectures. This integrated computational-experimental study establishes a clear inverse relationship between stacking fault energy and average twin spacing, offering a pathway for engineering nanostructured coatings with tailored twin networks and enhanced properties.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"306 ","pages":"Article 121890"},"PeriodicalIF":9.3,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145902588","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}
Pub Date : 2026-01-06DOI: 10.1016/j.actamat.2026.121904
Andrew J. Breen , William J. Davids , Hansheng Chen , Han Lin Mai , Keita Nomoto , Xiangyuan Cui , Xiaozhou Liao , Sophie Primig , Simon P. Ringer
Electron powder bed fusion has emerged as a promising additive manufacturing process for producing Ti-6Al-4V components with complex geometries. Although prior work has examined microstructural evolution phenomena including how thermal history influences the prevalence of specific α/α grain boundary misorientation intervariants governed by the Burgers orientation relationship between the α and β phases, the solute segregation behaviour at these interfaces remains poorly understood. This study employs correlative transmission Kikuchi diffraction and atom probe tomography to quantify the Gibbsian interfacial excess of V, Fe, and Al across multiple interfaces in electron powder bed fusion produced Ti-6Al-4V. V and Fe exhibited enrichment, while Al was depleted, with V segregation generally increasing with boundary misorientation. Spatial variations in segregation were observed across interface planes, although no consistent trend with boundary curvature was identified. First-principles calculations were also performed on model α/α grain boundaries to evaluate segregation energetics, confirming a thermodynamic preference for V enrichment and Al depletion. The agreement between experimental observations and theoretical predictions highlights the influence of local defect structures and atomic-scale interactions on segregation behaviour. These findings improve understanding of grain boundary chemistry in additively manufactured Ti alloys and provide a basis for future grain boundary engineering approaches aimed at tailoring interfacial properties.
{"title":"Quantifying changes to solute segregation behaviour at interfaces in additively manufactured Ti-6Al-4V","authors":"Andrew J. Breen , William J. Davids , Hansheng Chen , Han Lin Mai , Keita Nomoto , Xiangyuan Cui , Xiaozhou Liao , Sophie Primig , Simon P. Ringer","doi":"10.1016/j.actamat.2026.121904","DOIUrl":"10.1016/j.actamat.2026.121904","url":null,"abstract":"<div><div>Electron powder bed fusion has emerged as a promising additive manufacturing process for producing Ti-6Al-4V components with complex geometries. Although prior work has examined microstructural evolution phenomena including how thermal history influences the prevalence of specific α/α grain boundary misorientation intervariants governed by the Burgers orientation relationship between the α and β phases, the solute segregation behaviour at these interfaces remains poorly understood. This study employs correlative transmission Kikuchi diffraction and atom probe tomography to quantify the Gibbsian interfacial excess of V, Fe, and Al across multiple interfaces in electron powder bed fusion produced Ti-6Al-4V. V and Fe exhibited enrichment, while Al was depleted, with V segregation generally increasing with boundary misorientation. Spatial variations in segregation were observed across interface planes, although no consistent trend with boundary curvature was identified. First-principles calculations were also performed on model α/α grain boundaries to evaluate segregation energetics, confirming a thermodynamic preference for V enrichment and Al depletion. The agreement between experimental observations and theoretical predictions highlights the influence of local defect structures and atomic-scale interactions on segregation behaviour. These findings improve understanding of grain boundary chemistry in additively manufactured Ti alloys and provide a basis for future grain boundary engineering approaches aimed at tailoring interfacial properties.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"306 ","pages":"Article 121904"},"PeriodicalIF":9.3,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145902572","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}
Pub Date : 2026-01-05DOI: 10.1016/j.actamat.2026.121905
Jing-Qian Zhang , Zi-Ang Ma , Cong Xi , Yan Zhang , Wen-Xuan Lv , Chuan-Qi Cheng , Chun-Yan Han , Jing-Jing Wang , Shuang Li , Rui Zhang , Qianjin Guo , Jing Yang , Cun-Ku Dong , Hui Liu , Peng-Fei Yin , Xi-Wen Du
Metastable structures usually possess unique atomic and electronic configurations and thus show high potential on catalyzing chemical reactions. Among various metastable structures, surface single-atom alloys (SSAAs) attract widespread attention due to their ability to expose all dissimilar atoms on the surface, thereby regulating the electronic structure significantly. However, the synthesis of SSAAs remains a challenge due to the lack of effective methodology. Herein, we report a universal mechano-electrochemical technique for the synthesis of various SSAAs. Taking the Ni-Ag system as an example, the mechano-electrochemical process first drives nickel ions into Ag lattice, and then the embedded nickel ions are electrolytic reduced into nickel atoms, which are preferentially stabilized at the outermost surface, leading to the formation of SSAA. The produced self-supported electrode with SSAA exhibits excellent catalytic performance towards hydrogen evolution reaction, surpassing Ni-based catalysts and even Pt/C. This mechano-electrochemical technique can be applied to various immiscible alloy systems for the fabrication of SSAAs and then transform catalytically inert metals into high-performance catalysts.
{"title":"Mechano-electrochemical fabrication of self-supported Ag electrode with Ni surface single atom for hydrogen production","authors":"Jing-Qian Zhang , Zi-Ang Ma , Cong Xi , Yan Zhang , Wen-Xuan Lv , Chuan-Qi Cheng , Chun-Yan Han , Jing-Jing Wang , Shuang Li , Rui Zhang , Qianjin Guo , Jing Yang , Cun-Ku Dong , Hui Liu , Peng-Fei Yin , Xi-Wen Du","doi":"10.1016/j.actamat.2026.121905","DOIUrl":"10.1016/j.actamat.2026.121905","url":null,"abstract":"<div><div>Metastable structures usually possess unique atomic and electronic configurations and thus show high potential on catalyzing chemical reactions. Among various metastable structures, surface single-atom alloys (SSAAs) attract widespread attention due to their ability to expose all dissimilar atoms on the surface, thereby regulating the electronic structure significantly. However, the synthesis of SSAAs remains a challenge due to the lack of effective methodology. Herein, we report a universal mechano-electrochemical technique for the synthesis of various SSAAs. Taking the Ni-Ag system as an example, the mechano-electrochemical process first drives nickel ions into Ag lattice, and then the embedded nickel ions are electrolytic reduced into nickel atoms, which are preferentially stabilized at the outermost surface, leading to the formation of SSAA. The produced self-supported electrode with SSAA exhibits excellent catalytic performance towards hydrogen evolution reaction, surpassing Ni-based catalysts and even Pt/C. This mechano-electrochemical technique can be applied to various immiscible alloy systems for the fabrication of SSAAs and then transform catalytically inert metals into high-performance catalysts.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"306 ","pages":"Article 121905"},"PeriodicalIF":9.3,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145903350","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}
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