Pub Date : 2025-10-31DOI: 10.1016/j.mtla.2025.102593
Panpan Xu, Wentao Hao, Xiaole Qiu, Ensi Cao, Bing Sun
Bi-doped (In,Nb)TiO2 ceramics with nominal composition (Bi0.1In0.4Nb0.5)0.1Ti0.9O2 were synthesized to mitigate the high low-frequency dielectric losses present in undoped counterparts. The incorporation of Bi2O3 as a sintering aid significantly enhanced densification and effectively reduced the sintering temperature. Bi doping resulted in grain size refinement to 4.18–8.38 μm, increased the grain boundary area density, and facilitated the formation of insulating Bi2Ti2O7 secondary phases at the grain boundaries. These structural modifications decreased the low-frequency dielectric loss from over 0.1 to below 0.05, with a minimum of 0.042 at 300 Hz, while preserving the colossal permittivity. A novel dielectric relaxation phenomenon near 100 kHz was observed, which is explicitly attributed to Maxwell-Wagner interfacial polarization at the boundaries between semiconducting grains and insulating Bi2Ti2O7 secondary phases. Complex impedance analysis revealed that the enhanced grain boundary resistance was the primary factor responsible for the reduction in dielectric loss. XPS confirmed the coexistence of Ti3+/Ti4+ oxidation states and oxygen vacancies, indicating that the colossal permittivity originated from a combination of electron-pinned defect dipole behavior and internal barrier layer capacitor mechanisms.
{"title":"Synergistic grain boundary engineering and insulating phase formation for low-loss colossal permittivity in Bi-doped (In,Nb)TiO2 ceramics","authors":"Panpan Xu, Wentao Hao, Xiaole Qiu, Ensi Cao, Bing Sun","doi":"10.1016/j.mtla.2025.102593","DOIUrl":"10.1016/j.mtla.2025.102593","url":null,"abstract":"<div><div>Bi-doped (In,Nb)TiO<sub>2</sub> ceramics with nominal composition (Bi<sub>0.1</sub>In<sub>0.4</sub>Nb<sub>0.5</sub>)<sub>0.1</sub>Ti<sub>0.9</sub>O<sub>2</sub> were synthesized to mitigate the high low-frequency dielectric losses present in undoped counterparts. The incorporation of Bi<sub>2</sub>O<sub>3</sub> as a sintering aid significantly enhanced densification and effectively reduced the sintering temperature. Bi doping resulted in grain size refinement to 4.18–8.38 μm, increased the grain boundary area density, and facilitated the formation of insulating Bi<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> secondary phases at the grain boundaries. These structural modifications decreased the low-frequency dielectric loss from over 0.1 to below 0.05, with a minimum of 0.042 at 300 Hz, while preserving the colossal permittivity. A novel dielectric relaxation phenomenon near 100 kHz was observed, which is explicitly attributed to Maxwell-Wagner interfacial polarization at the boundaries between semiconducting grains and insulating Bi<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> secondary phases. Complex impedance analysis revealed that the enhanced grain boundary resistance was the primary factor responsible for the reduction in dielectric loss. XPS confirmed the coexistence of Ti<sup>3+</sup>/Ti<sup>4+</sup> oxidation states and oxygen vacancies, indicating that the colossal permittivity originated from a combination of electron-pinned defect dipole behavior and internal barrier layer capacitor mechanisms.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102593"},"PeriodicalIF":2.9,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-30DOI: 10.1016/j.mtla.2025.102591
Melika Mansouri Moghaddam , Rana Imani , Elaheh Jooybar , Martin Ehrbar
The treatment of significant bone defects often involves invasive surgeries and autologous bone grafting, highlighting the need for less invasive and more efficient alternatives. Existing injectable carriers often fail to provide both optimal mechanical support and a biologically favorable environment for mesenchymal stem cell (MSC) survival and osteogenic differentiation. Minimally invasive delivery of stem cells using engineered microcarriers represents a promising strategy to overcome these limitations. This study explores the potential of injectable hyaluronic acid (HA) and gelatin (Ge) microgels, chemically modified with tyramine (TA), for delivering human bone marrow-derived MSCs (hBM-MSCs) in bone regeneration. Microgels were fabricated via enzymatic crosslinking using horseradish peroxidase (HRP) and hydrogen peroxide (H₂O₂), and their physicochemical properties were systematically characterized. The average microgel sizes were 114.2 ± 42.2 µm (Ge-TA), 114.3 ± 31.6 µm (HA/Ge-TA), and 114.8 ± 30.0 µm (HA-TA). Surface analysis showed higher porosity in Ge-containing microgels, while enzymatic degradation revealed that HA incorporation improved structural stability. HA/Ge-TA microgels exhibited higher enzymatic stability than Ge-TA after 20 h of hyaluronidase and trypsin treatment, with average relative stability values of 1.53 and 1.22, respectively. Atomic force microscopy (AFM) measured stiffness as 1.83 ± 0.71 kPa (Ge-TA), 4.41 ± 0.68 kPa (HA/Ge-TA), and 11.79 ± 3.45 kPa (HA-TA). MTT assays demonstrated higher optical density (OD) in Ge-containing microgels at day 7 (Ge-TA: 0.328 ± 0.038; HA/Ge-TA: 0.299 ± 0.011; HA-TA: 0.143 ± 0.017). Osteogenic differentiation was significantly enhanced in HA/Ge-TA microgels, with alkaline phosphatase (ALP) activity at day 14 showing a 1.81-fold increase relative to TCP (1.807 ± 0.139), compared to 1.61 ± 0.072 for Ge-TA and 1.52 ± 0.284 for HA-TA. Alizarin Red S staining confirmed greater mineral deposition in HA/Ge-TA microgels (1.65 ± 0.08-fold increase relative to TCP). These findings suggest that HA/Ge-TA microgels offer an optimal balance of mechanical stability, cell viability, and osteoinductive capacity, representing a scalable, minimally invasive platform with significant potential for clinical translation in bone tissue engineering.
{"title":"Evaluation of osteogenic differentiation of stem cells on hyaluronic acid/gelatin microgels as 3D microcarriers for bone regeneration","authors":"Melika Mansouri Moghaddam , Rana Imani , Elaheh Jooybar , Martin Ehrbar","doi":"10.1016/j.mtla.2025.102591","DOIUrl":"10.1016/j.mtla.2025.102591","url":null,"abstract":"<div><div>The treatment of significant bone defects often involves invasive surgeries and autologous bone grafting, highlighting the need for less invasive and more efficient alternatives. Existing injectable carriers often fail to provide both optimal mechanical support and a biologically favorable environment for mesenchymal stem cell (MSC) survival and osteogenic differentiation. Minimally invasive delivery of stem cells using engineered microcarriers represents a promising strategy to overcome these limitations. This study explores the potential of injectable hyaluronic acid (HA) and gelatin (Ge) microgels, chemically modified with tyramine (TA), for delivering human bone marrow-derived MSCs (hBM-MSCs) in bone regeneration. Microgels were fabricated via enzymatic crosslinking using horseradish peroxidase (HRP) and hydrogen peroxide (H₂O₂), and their physicochemical properties were systematically characterized. The average microgel sizes were 114.2 ± 42.2 µm (Ge-TA), 114.3 ± 31.6 µm (HA/Ge-TA), and 114.8 ± 30.0 µm (HA-TA). Surface analysis showed higher porosity in Ge-containing microgels, while enzymatic degradation revealed that HA incorporation improved structural stability. HA/Ge-TA microgels exhibited higher enzymatic stability than Ge-TA after 20 h of hyaluronidase and trypsin treatment, with average relative stability values of 1.53 and 1.22, respectively. Atomic force microscopy (AFM) measured stiffness as 1.83 ± 0.71 kPa (Ge-TA), 4.41 ± 0.68 kPa (HA/Ge-TA), and 11.79 ± 3.45 kPa (HA-TA). MTT assays demonstrated higher optical density (OD) in Ge-containing microgels at day 7 (Ge-TA: 0.328 ± 0.038; HA/Ge-TA: 0.299 ± 0.011; HA-TA: 0.143 ± 0.017). Osteogenic differentiation was significantly enhanced in HA/Ge-TA microgels, with alkaline phosphatase (ALP) activity at day 14 showing a 1.81-fold increase relative to TCP (1.807 ± 0.139), compared to 1.61 ± 0.072 for Ge-TA and 1.52 ± 0.284 for HA-TA. Alizarin Red S staining confirmed greater mineral deposition in HA/Ge-TA microgels (1.65 ± 0.08-fold increase relative to TCP). These findings suggest that HA/Ge-TA microgels offer an optimal balance of mechanical stability, cell viability, and osteoinductive capacity, representing a scalable, minimally invasive platform with significant potential for clinical translation in bone tissue engineering.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102591"},"PeriodicalIF":2.9,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-29DOI: 10.1016/j.mtla.2025.102592
Mujtaba Rafique Ghoto , B. Hayden Daubert , Deborah ParraCervantes , August J. Hemmerla , Bret D. Ulery , W. David Hairston , Christopher G. Sinks , Stephan Young , Christopher S. O’Bryan
Phantoms are test specimens and models that mimic the material properties and imaging modalities of tissues. To replicate the high water content and low moduli of many soft tissues, phantom models often use highly swollen polymer networks, i.e., hydrogels, as surrogate tissue-like materials. These hydrogels begin as polymer solutions before undergoing gelation or crosslinking to form soft elastic solids. As such, manufacturing of hydrogel phantom models has largely focused on casting the polymer precursor into pre-defined molds before initiating gelation, limiting the ability to incorporate structural and chemical complexities within soft tissue phantom models. Alternatively, embedded 3D-printing enables hydrogel precursors solutions to be structured in their fluid phase, providing new opportunities for manufacturing anthropomorphic soft tissue phantom models. Here, we design a photo-crosslinkable poly(vinyl alcohol) methacrylate (PVA-MA) polymer by attaching methacrylate groups to poly(vinyl alcohol) through a transesterification reaction and demonstrate its application as a tissue-equivalent material to manufacture anthropomorphic phantom models that imitate material characteristics of soft tissues. As part of this study, we characterize the mechanical, thermal, and electromagnetic properties of the PVA-MA hydrogels and demonstrate that these properties can be tuned to replicate the material properties of native tissue. Further, we explore the relationships between the shear viscosity of the polymer solution, the material properties of the support bath, and the resulting cross-sectional area of printed filaments to identify design principles for 3D-printing PVA-MA polymer solutions. Finally, we apply these principles to manufacture a scale model of a human brain using a solid model generated from a medical scan of a human brain.
{"title":"3D-printing soft tissue phantom models from photo-crosslinkable poly(vinyl alcohol) methacrylate","authors":"Mujtaba Rafique Ghoto , B. Hayden Daubert , Deborah ParraCervantes , August J. Hemmerla , Bret D. Ulery , W. David Hairston , Christopher G. Sinks , Stephan Young , Christopher S. O’Bryan","doi":"10.1016/j.mtla.2025.102592","DOIUrl":"10.1016/j.mtla.2025.102592","url":null,"abstract":"<div><div>Phantoms are test specimens and models that mimic the material properties and imaging modalities of tissues. To replicate the high water content and low moduli of many soft tissues, phantom models often use highly swollen polymer networks, <em>i.e.</em>, hydrogels, as surrogate tissue-like materials. These hydrogels begin as polymer solutions before undergoing gelation or crosslinking to form soft elastic solids. As such, manufacturing of hydrogel phantom models has largely focused on casting the polymer precursor into pre-defined molds before initiating gelation, limiting the ability to incorporate structural and chemical complexities within soft tissue phantom models. Alternatively, embedded 3D-printing enables hydrogel precursors solutions to be structured in their fluid phase, providing new opportunities for manufacturing anthropomorphic soft tissue phantom models. Here, we design a photo-crosslinkable poly(vinyl alcohol) methacrylate (PVA-MA) polymer by attaching methacrylate groups to poly(vinyl alcohol) through a transesterification reaction and demonstrate its application as a tissue-equivalent material to manufacture anthropomorphic phantom models that imitate material characteristics of soft tissues. As part of this study, we characterize the mechanical, thermal, and electromagnetic properties of the PVA-MA hydrogels and demonstrate that these properties can be tuned to replicate the material properties of native tissue. Further, we explore the relationships between the shear viscosity of the polymer solution, the material properties of the support bath, and the resulting cross-sectional area of printed filaments to identify design principles for 3D-printing PVA-MA polymer solutions. Finally, we apply these principles to manufacture a scale model of a human brain using a solid model generated from a medical scan of a human brain.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102592"},"PeriodicalIF":2.9,"publicationDate":"2025-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-27DOI: 10.1016/j.mtla.2025.102590
Xin Zhao , Mengdi Zhang , Hanqing Xu , Zhuoyi Wang , Tianming Li , Rui Li
Limited by traditional trial-and-error methods, it is a great challenge to develop novel high-entropy alloys (HEAs) with an FCC+BCC dual-phase structure and excellent corrosion resistance. Herein, this study developed a machine learning (ML)-based design method, which predicted the influence of Al-Ti co-doping on the phase structure of CoCrNi-based HEAs and used this as a screening criterion to obtain the target alloys. After model optimization and comparative evaluation, the Random Forest (RF) algorithm was ultimately selected for phase prediction, achieving an accuracy of 94.1 %. To verify the accuracy of the machine learning phase prediction model, two types of HEAs were designed: one is composed of (CoCrNi)94Al3Ti3, (CoCrNi)94Al4Ti2, and (CoCrNi)93Al4Ti3 with a single FCC structure, and the other comprises (CoCrNi)90Al5Ti5, (CoCrNi)85Al8Ti7, and (CoCrNi)80Al10Ti10 with an FCC+BCC dual-phase structure. SHAP analysis was employed to enhance the interpretability of the model, and the results showed that valence electron concentration (VEC) exerts the most significant influence on phase formation. In addition, electrochemical test results of the FCC+BCC dual-phase HEAs in Ringer's solution indicated that the Al5Ti5 alloy exhibits the optimal corrosion resistance, with a corrosion current density of 8.08×10⁻⁸ A/cm², a pitting potential of 840.6 mV, and a passive region of 1062.4 mV.
{"title":"Machine learning-driven phase prediction and corrosion behavior of (CoCrNi)(100-x-y) AlxTiy high-entropy alloys in Ringer's solution","authors":"Xin Zhao , Mengdi Zhang , Hanqing Xu , Zhuoyi Wang , Tianming Li , Rui Li","doi":"10.1016/j.mtla.2025.102590","DOIUrl":"10.1016/j.mtla.2025.102590","url":null,"abstract":"<div><div>Limited by traditional trial-and-error methods, it is a great challenge to develop novel high-entropy alloys (HEAs) with an FCC+BCC dual-phase structure and excellent corrosion resistance. Herein, this study developed a machine learning (ML)-based design method, which predicted the influence of Al-Ti co-doping on the phase structure of CoCrNi-based HEAs and used this as a screening criterion to obtain the target alloys. After model optimization and comparative evaluation, the Random Forest (RF) algorithm was ultimately selected for phase prediction, achieving an accuracy of 94.1 %. To verify the accuracy of the machine learning phase prediction model, two types of HEAs were designed: one is composed of (CoCrNi)<sub>94</sub>Al<sub>3</sub>Ti<sub>3</sub>, (CoCrNi)<sub>94</sub>Al<sub>4</sub>Ti<sub>2</sub>, and (CoCrNi)<sub>93</sub>Al<sub>4</sub>Ti<sub>3</sub> with a single FCC structure, and the other comprises (CoCrNi)<sub>90</sub>Al<sub>5</sub>Ti<sub>5</sub>, (CoCrNi)<sub>85</sub>Al<sub>8</sub>Ti<sub>7</sub>, and (CoCrNi)<sub>80</sub>Al<sub>10</sub>Ti<sub>10</sub> with an FCC+BCC dual-phase structure. SHAP analysis was employed to enhance the interpretability of the model, and the results showed that valence electron concentration (<em>VEC</em>) exerts the most significant influence on phase formation. In addition, electrochemical test results of the FCC+BCC dual-phase HEAs in Ringer's solution indicated that the Al<sub>5</sub>Ti<sub>5</sub> alloy exhibits the optimal corrosion resistance, with a corrosion current density of 8.08×10⁻⁸ A/cm², a pitting potential of 840.6 mV, and a passive region of 1062.4 mV.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102590"},"PeriodicalIF":2.9,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-25DOI: 10.1016/j.mtla.2025.102589
Jiaqing Zhang, Ru Lin, Qingshan Lu
Supercapacitors as an energy storage device exhibit high-power density, long cycle life, and rapid charge-discharge capability. Electrode materials play an important role on the electrochemical performance of supercapacitors. Porous NiO films are fabricated through a two-step process of electrodeposition and electrochemical dealloying combined with thermal oxidation. X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning electron microscopy were used to studied the phase and microstructure. The NiO film exhibits a porous structure with an average pore size of 100 nm. The electrochemical performance of porous NiO films is optimized by controlling the electrochemical parameters including deposition current density, deposition time, and dealloying time. The optimized sample exhibits a high specific capacitance of 1007.5 F/g at 1 A/g. The unique porous structure enables the numerous redox-active sites at high current density, resulting in high specific capacitance of 1055.2 F/g at 10 A/g, which achieves an increase of 47.5 F/g compared to that at 1 A/g. Moreover, 90.4% of the initial capacitance is maintained after 3000 cycles. This outstanding performance can be attributed to the unique characteristics of porous structure with high surface areas and easy ion transport for electrochemical reactions.
超级电容器作为一种能量存储器件，具有功率密度高、循环寿命长、充放电速度快等特点。电极材料对超级电容器的电化学性能起着至关重要的作用。采用电沉积和电化学脱合金结合热氧化两步法制备了多孔NiO膜。采用x射线衍射、x射线光电子能谱、拉曼光谱和扫描电镜对其物相和微观结构进行了研究。所制备的NiO薄膜具有平均孔径为100nm的多孔结构。通过控制沉积电流密度、沉积时间和脱合金时间等电化学参数，优化多孔NiO膜的电化学性能。优化后的样品在1 a /g时具有1007.5 F/g的高比电容。独特的多孔结构使其在高电流密度下具有大量的氧化还原活性位点，从而在10 A/g时具有1055.2 F/g的高比电容，比1 A/g时提高了47.5 F/g。此外，在3000次循环后，90.4%的初始电容保持不变。这种优异的性能可归因于其独特的多孔结构，具有高表面积和易于离子传输的电化学反应特性。
{"title":"Influence of electrodeposition and dealloying on electrochemical properties of porous nickel oxide","authors":"Jiaqing Zhang, Ru Lin, Qingshan Lu","doi":"10.1016/j.mtla.2025.102589","DOIUrl":"10.1016/j.mtla.2025.102589","url":null,"abstract":"<div><div>Supercapacitors as an energy storage device exhibit high-power density, long cycle life, and rapid charge-discharge capability. Electrode materials play an important role on the electrochemical performance of supercapacitors. Porous NiO films are fabricated through a two-step process of electrodeposition and electrochemical dealloying combined with thermal oxidation. X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning electron microscopy were used to studied the phase and microstructure. The NiO film exhibits a porous structure with an average pore size of 100 nm. The electrochemical performance of porous NiO films is optimized by controlling the electrochemical parameters including deposition current density, deposition time, and dealloying time. The optimized sample exhibits a high specific capacitance of 1007.5 F/g at 1 A/g. The unique porous structure enables the numerous redox-active sites at high current density, resulting in high specific capacitance of 1055.2 F/g at 10 A/g, which achieves an increase of 47.5 F/g compared to that at 1 A/g. Moreover, 90.4% of the initial capacitance is maintained after 3000 cycles. This outstanding performance can be attributed to the unique characteristics of porous structure with high surface areas and easy ion transport for electrochemical reactions.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102589"},"PeriodicalIF":2.9,"publicationDate":"2025-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-22DOI: 10.1016/j.mtla.2025.102587
Divya Sri Bandla , Atul H. Chokshi
Concentrated solid solution alloys such as NiCoCr and NiCoCrFe are well known for their low stacking fault energies and promising mechanical properties at low temperatures. However, their high temperature deformation has not been well established. The present study deals with the high temperature creep behavior of these alloys. Both alloys had a single phase solid solution with FCC crystal structure which was not altered by creep deformation. The room temperature stacking fault energies of NiCoCr and NiCoCrFe alloys were evaluated to be in the range of 14 – 27 mJ m−2 and 11 – 26 mJ m−2, respectively. The dominating creep mechanism in these alloys at 990 K was observed to be dislocation climb and there was no significant difference in the creep rates of alloys. The creep deformation resulted in a planar band structure in both alloys. Despite multiple principal elements in NiCoCr and NiCoCrFe alloys, the atomic misfit parameters of these alloys were calculated to be low which resulted in poor solute drag influence on the dislocation climb as compared to vacancy diffusion. A comparison between the creep rates of NiCoCr and NiCoCrFe alloys from the present study with that of a binary Ni – 60 Co system which had a similar room temperature stacking fault energy revealed significantly lower creep rates in NiCoCr and NiCoCrFe alloys.
{"title":"Insights into the creep behavior of Ni based concentrated solid solution alloys","authors":"Divya Sri Bandla , Atul H. Chokshi","doi":"10.1016/j.mtla.2025.102587","DOIUrl":"10.1016/j.mtla.2025.102587","url":null,"abstract":"<div><div>Concentrated solid solution alloys such as NiCoCr and NiCoCrFe are well known for their low stacking fault energies and promising mechanical properties at low temperatures. However, their high temperature deformation has not been well established. The present study deals with the high temperature creep behavior of these alloys. Both alloys had a single phase solid solution with FCC crystal structure which was not altered by creep deformation. The room temperature stacking fault energies of NiCoCr and NiCoCrFe alloys were evaluated to be in the range of 14 – 27 mJ m<sup>−2</sup> and 11 – 26 mJ m<sup>−2</sup>, respectively. The dominating creep mechanism in these alloys at 990 K was observed to be dislocation climb and there was no significant difference in the creep rates of alloys. The creep deformation resulted in a planar band structure in both alloys. Despite multiple principal elements in NiCoCr and NiCoCrFe alloys, the atomic misfit parameters of these alloys were calculated to be low which resulted in poor solute drag influence on the dislocation climb as compared to vacancy diffusion. A comparison between the creep rates of NiCoCr and NiCoCrFe alloys from the present study with that of a binary Ni – 60 Co system which had a similar room temperature stacking fault energy revealed significantly lower creep rates in NiCoCr and NiCoCrFe alloys.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102587"},"PeriodicalIF":2.9,"publicationDate":"2025-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-20DOI: 10.1016/j.mtla.2025.102588
Hyungjin Nam , Jaewon Lee , Seongjun Kim , InJoon Sohn , Kyyoul Yun , Chanwon Jung , Seonghoon Yi
Fe-based amorphous soft magnetic materials have emerged as promising candidates for high-frequency magnetic core applications, as microstructural modification can effectively suppress eddy current loss and thereby minimize the overall core loss. In this study, high-density soft magnetic cores were successfully fabricated using Fe75.5-x(C, Si, B, P)24.5(Cr, Al)x (x = 2.0 and 4.3) amorphous flakes. The amorphous-derived superplasticity enabled severe plastic deformation during sintering without crystallization, resulting in highly densified compacts with relative densities of 96.3 % and 98.0 % for the x = 2.0 and x = 4.3 specimens, respectively. This densification minimized degradation in saturation magnetic flux density and permeability, while maintaining acceptable coercivity. SiO₂ insulation coatings significantly reduced the eddy current loss at 1000 Hz, thereby decreasing the core loss from 1.98 to 1.03 W/kg for x = 2.0 specimen and from 2.03 to 1.28 W/kg for x = 4.3 specimen after coating. The sintered cores also exhibited sufficient hardness. These findings highlight a promising processing route for achieving low-loss, high-performance soft magnetic materials by leveraging superplastic sintering of amorphous precursors.
{"title":"Amorphous-derived superplasticity for high-density soft magnetic cores with reduced core loss","authors":"Hyungjin Nam , Jaewon Lee , Seongjun Kim , InJoon Sohn , Kyyoul Yun , Chanwon Jung , Seonghoon Yi","doi":"10.1016/j.mtla.2025.102588","DOIUrl":"10.1016/j.mtla.2025.102588","url":null,"abstract":"<div><div>Fe-based amorphous soft magnetic materials have emerged as promising candidates for high-frequency magnetic core applications, as microstructural modification can effectively suppress eddy current loss and thereby minimize the overall core loss. In this study, high-density soft magnetic cores were successfully fabricated using Fe<sub>75.5-x</sub>(C, Si, B, P)<sub>24.5</sub>(Cr, Al)<sub>x</sub> (<em>x</em> = 2.0 and 4.3) amorphous flakes. The amorphous-derived superplasticity enabled severe plastic deformation during sintering without crystallization, resulting in highly densified compacts with relative densities of 96.3 % and 98.0 % for the <em>x</em> = 2.0 and <em>x</em> = 4.3 specimens, respectively. This densification minimized degradation in saturation magnetic flux density and permeability, while maintaining acceptable coercivity. SiO₂ insulation coatings significantly reduced the eddy current loss at 1000 Hz, thereby decreasing the core loss from 1.98 to 1.03 W/kg for <em>x</em> = 2.0 specimen and from 2.03 to 1.28 W/kg for <em>x</em> = 4.3 specimen after coating. The sintered cores also exhibited sufficient hardness. These findings highlight a promising processing route for achieving low-loss, high-performance soft magnetic materials by leveraging superplastic sintering of amorphous precursors.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102588"},"PeriodicalIF":2.9,"publicationDate":"2025-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-20DOI: 10.1016/j.mtla.2025.102584
Longwei Zhao , Xiaodong Zhu , Huixia Xu , Kaiming Cheng , Jin Wang , Dongqing Zhao , Junpeng Duan , Cunliang Sun , Jixue Zhou , Yong Du
This study investigates grain boundary (GB) segregation behavior in a Mg-2 at.% Y alloy by combining high-resolution transmission electron microscopy (TEM) with thermodynamic modeling. The segregation characteristics of Y at GBs and their evolution with temperature were systematically examined. Experimental results reveal pronounced segregation of Y at high-angle asymmetric grain boundaries, with the segregation layer thickness increasing with annealing temperature. Elemental line scans and HAADF-STEM imaging show that the peak concentration of Y shifts toward one side of the boundary, indicating the influence of GB structure on segregation behavior. To further understand the thermodynamic mechanism underlying this phenomenon, a GB λ-phase (λ represents the segregation layer thickness at GB) diagram was constructed based on the disordered quasi-liquid model. The model predicts the variation of segregation layer thickness with temperature and alloy composition, and the results were compared with experimental data. It was found that although both the segregation driving force and the formation free energy decrease with increasing temperature, the latter declines more rapidly, resulting in an overall increase in the segregation layer thickness. Additionally, the GB segregation composition decreases with temperature, suggesting reduced solute stability at elevated temperatures. This work elucidates the thermodynamic evolution of GB segregation in Mg-Y alloys from both experimental and theoretical perspectives, verifies the applicability of GB phase diagram modeling based on interface thermodynamics, and provides a theoretical framework and methodological base for GB engineering in polycrystalline lightweight Mg alloy systems.
{"title":"Experimental characterization and thermodynamic mapping of grain boundary segregation in Mg-2Y alloy","authors":"Longwei Zhao , Xiaodong Zhu , Huixia Xu , Kaiming Cheng , Jin Wang , Dongqing Zhao , Junpeng Duan , Cunliang Sun , Jixue Zhou , Yong Du","doi":"10.1016/j.mtla.2025.102584","DOIUrl":"10.1016/j.mtla.2025.102584","url":null,"abstract":"<div><div>This study investigates grain boundary (GB) segregation behavior in a Mg-2 at.% Y alloy by combining high-resolution transmission electron microscopy (TEM) with thermodynamic modeling. The segregation characteristics of Y at GBs and their evolution with temperature were systematically examined. Experimental results reveal pronounced segregation of Y at high-angle asymmetric grain boundaries, with the segregation layer thickness increasing with annealing temperature. Elemental line scans and HAADF-STEM imaging show that the peak concentration of Y shifts toward one side of the boundary, indicating the influence of GB structure on segregation behavior. To further understand the thermodynamic mechanism underlying this phenomenon, a GB λ-phase (λ represents the segregation layer thickness at GB) diagram was constructed based on the disordered quasi-liquid model. The model predicts the variation of segregation layer thickness with temperature and alloy composition, and the results were compared with experimental data. It was found that although both the segregation driving force and the formation free energy decrease with increasing temperature, the latter declines more rapidly, resulting in an overall increase in the segregation layer thickness. Additionally, the GB segregation composition decreases with temperature, suggesting reduced solute stability at elevated temperatures. This work elucidates the thermodynamic evolution of GB segregation in Mg-Y alloys from both experimental and theoretical perspectives, verifies the applicability of GB phase diagram modeling based on interface thermodynamics, and provides a theoretical framework and methodological base for GB engineering in polycrystalline lightweight Mg alloy systems.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102584"},"PeriodicalIF":2.9,"publicationDate":"2025-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-19DOI: 10.1016/j.mtla.2025.102586
Zhenghua Guo , An Lu , Mingjie Zhao , Lihong Jiang , Guangang Wang
The effects of bainite transformation on the mechanical properties of 300 M ultra-high strength steel (UHSS) fabricated by power plasma arc additive manufacturing (PPA-AM) are examined. The results indicate that there are three primary thermal cycles during the PPA-AM process, including austenitizing (Type I), high-temperature tempering (Type II), and low-temperature tempering (Type III). The thermal cycle varies with interlayer temperature, significantly affecting the microstructure characteristics across different regions of the power plasma arc additively manufactured (PPA-AMed) component. The top region predominantly consists of untempered martensite (UTM), while the middle and bottom areas are composed of tempered martensite (TM), needle-like bainite (NLB), and feather-like bainite (FLB). Elevated interlayer temperatures and proximity to the substrate can enhance thermal cycling effects, facilitating a more complete transformation to FLB. The bainite transformation of PPA-AMed 300 M steel follows a superledges growth mechanism initiated by shear nucleation of martensite, and then growing into FLB under the subsequent thermal cycling effect. Notably, the bainite morphology exhibits significant variation depending on different thermal cycle types. Tensile tests indicate that the top region achieves a peak tensile strength of 2151 MPa at an interlayer temperature of 200°C, attributed to the refinement of martensite by fine NLB within cellular grains and the formation of substructures. As the interlayer temperature increases, the fracture mode transitions from a ductile-brittle mixed mode to brittle fracture, and eventually to ductile fracture.
{"title":"Effects of bainite transformation on mechanical properties of 300 M ultra-high strength steel fabricated by power plasma arc additive manufacturing","authors":"Zhenghua Guo , An Lu , Mingjie Zhao , Lihong Jiang , Guangang Wang","doi":"10.1016/j.mtla.2025.102586","DOIUrl":"10.1016/j.mtla.2025.102586","url":null,"abstract":"<div><div>The effects of bainite transformation on the mechanical properties of 300 M ultra-high strength steel (UHSS) fabricated by power plasma arc additive manufacturing (PPA-AM) are examined. The results indicate that there are three primary thermal cycles during the PPA-AM process, including austenitizing (Type I), high-temperature tempering (Type II), and low-temperature tempering (Type III). The thermal cycle varies with interlayer temperature, significantly affecting the microstructure characteristics across different regions of the power plasma arc additively manufactured (PPA-AMed) component. The top region predominantly consists of untempered martensite (UTM), while the middle and bottom areas are composed of tempered martensite (TM), needle-like bainite (NLB), and feather-like bainite (FLB). Elevated interlayer temperatures and proximity to the substrate can enhance thermal cycling effects, facilitating a more complete transformation to FLB. The bainite transformation of PPA-AMed 300 M steel follows a superledges growth mechanism initiated by shear nucleation of martensite, and then growing into FLB under the subsequent thermal cycling effect. Notably, the bainite morphology exhibits significant variation depending on different thermal cycle types. Tensile tests indicate that the top region achieves a peak tensile strength of 2151 MPa at an interlayer temperature of 200°C, attributed to the refinement of martensite by fine NLB within cellular grains and the formation of substructures. As the interlayer temperature increases, the fracture mode transitions from a ductile-brittle mixed mode to brittle fracture, and eventually to ductile fracture.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102586"},"PeriodicalIF":2.9,"publicationDate":"2025-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-19DOI: 10.1016/j.mtla.2025.102585
Junwei Peng , Shaoyuan Lyu , Zhongyang Liu , Guodong Li , Ruixiao Zheng , Minfang Chen , Chaoli Ma
High strength low-alloyed Mg-1Zn-0.3Mn (ZM) alloys with different of Sm contents (0, 1 and 2wt%) were fabricated via hot extrusion. The evolution of microstructure and mechanical property of these alloys were investigated. The results showed that the incorporation of Sm altered the grain structure and secondary phase precipitation behavior of the alloys, resulting in exceptional tensile yield strength (∼383 MPa) coupled with a fracture elongation of 4.2% in the extruded Mg-1Zn-0.3Mn-2Sm (ZMS2) alloy. As the increase of Sm content, the volume fraction of second phases increased both in as-cast and extruded alloys. Meanwhile, the recrystallization ratio in extruded alloy decreased from nearly 100% in ZM alloy to 69.4% and 61.4% in ZMS1 and ZMS2, respectively. Moreover, the grain size in dynamical regions decreased from 1.92 µm (ZM) to 0.69 µm (ZMS2). Further analysis revealed that the large number of (Mg,Zn)3Sm phases in Sm containing alloy, fine grains and dislocation strengthening contributed the high strength of ZMS alloys.
{"title":"Exploring the evolution of microstructure and mechanical property of low-alloyed Mg-Zn-Mn alloy with Sm addition","authors":"Junwei Peng , Shaoyuan Lyu , Zhongyang Liu , Guodong Li , Ruixiao Zheng , Minfang Chen , Chaoli Ma","doi":"10.1016/j.mtla.2025.102585","DOIUrl":"10.1016/j.mtla.2025.102585","url":null,"abstract":"<div><div>High strength low-alloyed Mg-1Zn-0.3Mn (ZM) alloys with different of Sm contents (0, 1 and 2wt%) were fabricated via hot extrusion. The evolution of microstructure and mechanical property of these alloys were investigated. The results showed that the incorporation of Sm altered the grain structure and secondary phase precipitation behavior of the alloys, resulting in exceptional tensile yield strength (∼383 MPa) coupled with a fracture elongation of 4.2% in the extruded Mg-1Zn-0.3Mn-2Sm (ZMS2) alloy. As the increase of Sm content, the volume fraction of second phases increased both in as-cast and extruded alloys. Meanwhile, the recrystallization ratio in extruded alloy decreased from nearly 100% in ZM alloy to 69.4% and 61.4% in ZMS1 and ZMS2, respectively. Moreover, the grain size in dynamical regions decreased from 1.92 µm (ZM) to 0.69 µm (ZMS2). Further analysis revealed that the large number of (Mg,Zn)<sub>3</sub>Sm phases in Sm containing alloy, fine grains and dislocation strengthening contributed the high strength of ZMS alloys.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102585"},"PeriodicalIF":2.9,"publicationDate":"2025-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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