Pub Date : 2024-10-09DOI: 10.1016/j.actamat.2024.120458
Bin Xu , Fengwen Mu , Yingzhou Liu , Rulei Guo , Shiqian Hu , Junichiro Shiomi
Thermal boundary resistance (TBR) in semiconductor-on-diamond structure bottlenecks efficient heat dissipation in electronic devices. In this study, to reduce the TBR between GaN and diamond, surface-activated bonding with a hybrid SiOx-Ar ion source was initially applied to achieve an ultrathin interfacial layer. The simultaneous surface activation and slow deposition of the SiOx binder layer enabled precise control over layer thickness (2.5–5.3 nm) and formation of an amorphous heterogeneous nanostructure comprising a SiOx region between two inter-diffusion regions. Crucially, the 2.5-nm-thick interfacial layer achieved a TBR of 8.3 m2⋅K/GW, a record low for direct-bonded GaN/diamond interface. A remarkable feature is that the TBR is extremely sensitive to the interfacial thickness; Varying from 8.3 m2⋅K/GW to 34 m2⋅K/GW with thickness difference of only 2.8 nm. Theoretical analysis revealed the origin of this phenomena: a diamond/SiOx inter-diffusion layer extend the vibrational frequency, far exceeding that of crystalline diamond, which increases the lattice vibrational mismatch and suppresses phonon transmission.
{"title":"Record-Low thermal boundary resistance at bonded GaN/diamond interface by controlling ultrathin heterogeneous amorphous layer","authors":"Bin Xu , Fengwen Mu , Yingzhou Liu , Rulei Guo , Shiqian Hu , Junichiro Shiomi","doi":"10.1016/j.actamat.2024.120458","DOIUrl":"10.1016/j.actamat.2024.120458","url":null,"abstract":"<div><div>Thermal boundary resistance (TBR) in semiconductor-on-diamond structure bottlenecks efficient heat dissipation in electronic devices. In this study, to reduce the TBR between GaN and diamond, surface-activated bonding with a hybrid SiO<sub>x</sub>-Ar ion source was initially applied to achieve an ultrathin interfacial layer. The simultaneous surface activation and slow deposition of the SiO<sub>x</sub> binder layer enabled precise control over layer thickness (2.5–5.3 nm) and formation of an amorphous heterogeneous nanostructure comprising a SiO<sub>x</sub> region between two inter-diffusion regions. Crucially, the 2.5-nm-thick interfacial layer achieved a TBR of 8.3 m<sup>2</sup>⋅K/GW, a record low for direct-bonded GaN/diamond interface. A remarkable feature is that the TBR is extremely sensitive to the interfacial thickness; Varying from 8.3 m<sup>2</sup>⋅K/GW to 34 m<sup>2</sup>⋅K/GW with thickness difference of only 2.8 nm. Theoretical analysis revealed the origin of this phenomena: a diamond/SiO<sub>x</sub> inter-diffusion layer extend the vibrational frequency, far exceeding that of crystalline diamond, which increases the lattice vibrational mismatch and suppresses phonon transmission.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120458"},"PeriodicalIF":8.3,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142386153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-09DOI: 10.1016/j.actamat.2024.120459
Sourav Sahoo , Sajid Mannan , Utkarsh Tiwari , Romit Rajendra Kaware , Zhijiang Ye , Nitya Nand Gosvami , N. M. Anoop Krishnan
Understanding the mechanism of scratch damage is vital to developing better scratch-resistant glasses. To this extent, employing molecular dynamics simulations and experiments, we investigate the scratch damage of silica glass against a rigid diamond indenter. The glass surface is pre-indented to a constant depth and then dragged to simulate a linear scratch, and the structural impact in the indent-to-scratch transitioning phase is examined. We observe that despite the differences in length and timescales, the simulated values of indentation hardness and coefficient of friction exhibit excellent agreement with experimental values from nanoindentation and atomic force microscopy experiments. Interestingly, analysis of the subsurface deformation in the scratched region reveals densification and shear flow, in contrast to pure densification, as in the case of indentation. Furthermore, similar percentages of recovery from experiments and simulation reveal that the reversible component of plastic deformation owing to densification is comparable in both cases. Finally, in contrast to the common hypothesis, we demonstrate that while the bond angles and lengths recover significantly, the ring structure does not recover upon annealing, although they exhibit some relaxation. Thus, the present study sheds new light on the crucial role of the medium-range structure of glasses subjected to scratch deformation.
{"title":"Atomistic insights into scratch-induced structural evolution of silica glass","authors":"Sourav Sahoo , Sajid Mannan , Utkarsh Tiwari , Romit Rajendra Kaware , Zhijiang Ye , Nitya Nand Gosvami , N. M. Anoop Krishnan","doi":"10.1016/j.actamat.2024.120459","DOIUrl":"10.1016/j.actamat.2024.120459","url":null,"abstract":"<div><div>Understanding the mechanism of scratch damage is vital to developing better scratch-resistant glasses. To this extent, employing molecular dynamics simulations and experiments, we investigate the scratch damage of silica glass against a rigid diamond indenter. The glass surface is pre-indented to a constant depth and then dragged to simulate a linear scratch, and the structural impact in the indent-to-scratch transitioning phase is examined. We observe that despite the differences in length and timescales, the simulated values of indentation hardness and coefficient of friction exhibit excellent agreement with experimental values from nanoindentation and atomic force microscopy experiments. Interestingly, analysis of the subsurface deformation in the scratched region reveals densification and shear flow, in contrast to pure densification, as in the case of indentation. Furthermore, similar percentages of recovery from experiments and simulation reveal that the reversible component of plastic deformation owing to densification is comparable in both cases. Finally, in contrast to the common hypothesis, we demonstrate that while the bond angles and lengths recover significantly, the ring structure does not recover upon annealing, although they exhibit some relaxation. Thus, the present study sheds new light on the crucial role of the medium-range structure of glasses subjected to scratch deformation.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120459"},"PeriodicalIF":8.3,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142386178","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 : 2024-10-09DOI: 10.1016/j.actamat.2024.120452
Jie Qi, David C. Dunand
This study investigates, both experimentally and via machine-learning modeling, the strengthening mechanisms and effects of Mg and Ni additions to Al-MM (mischmetal, a sustainable Ce+La+Nd mixture to replace Ce) alloys, aiming to develop creep- and coarsening-resistant Al-MM-Mg-Ni alloys with a focus on twin eutectic co-solidification microstructures. Based on near-eutectic Al-9MM (wt%) alloy, the Mg and Ni additions introduce solid-solution and eutectic strengthening, respectively. Ternary hypo-eutectic Al-9MM-0.25/0.5/0.75Mg variants improve hardness up to 592 MPa. Ternary Al-9MM-2/4Ni display hypo-eutectic microstructures. Al-9MM-2Ni shows separated growth of Al11MM3 and Al3Ni eutectic phases, while Al-9MM-4Ni features finely intertwined Al11MM3-Al3Ni fibers from co-solidification. The hyper-eutectic Al-9MM-5Ni contains primary Al3Ni particles alongside the intertwined fibers, raising the hardness to 739 MPa. Finally, quaternary Al-9MM-0.5/0.75Mg-4/4.5Ni alloys maintain hypo-eutectic microstructures with a significant increase of hardness to 929 MPa. The series Al-9MM, Al-9MM-0.75Mg, Al-9MM-4Ni, and Al-9MM-4.5Ni-0.75Mg exhibits increasing tensile yield strengths of 70, 83, 88, and 105 MPa, with decreasing ductility of 12.0, 5.8, 2.0, and 0.8 %. All Al-9MM-Mg-Ni alloys exhibit excellent hardness retention and coarsening resistance after thermal exposure at 300 or 350°C for up to 11 weeks. A machine-learning model accurately predicts the alloy's hardness evolution under thermal exposure. Feature analysis quantitively shows the strengthening impact of MM, Ni, and Mg addition and demonstrate enhanced strengthening retention, under thermal exposure, of Al11MM3 over Al3Ni, alongside the beneficial effects of Mg homogenization. At 300 °C, Al-9MM-Mg-Ni alloys demonstrate higher creep resistance than most precipitation-strengthened Al-Sc-Zr-based alloys and solid-solution-strengthened Al-Mg alloys, with Al-9MM-4Ni as the best performer.
{"title":"Strengthening effects from Mg and Ni in Al-mischmetal eutectic alloys: Insights from microstructures and Bayesian analysis","authors":"Jie Qi, David C. Dunand","doi":"10.1016/j.actamat.2024.120452","DOIUrl":"10.1016/j.actamat.2024.120452","url":null,"abstract":"<div><div>This study investigates, both experimentally and via machine-learning modeling, the strengthening mechanisms and effects of Mg and Ni additions to Al-MM (mischmetal, a sustainable Ce+La+Nd mixture to replace Ce) alloys, aiming to develop creep- and coarsening-resistant Al-MM-Mg-Ni alloys with a focus on twin eutectic co-solidification microstructures. Based on near-eutectic Al-9MM (wt%) alloy, the Mg and Ni additions introduce solid-solution and eutectic strengthening, respectively. Ternary hypo-eutectic Al-9MM-0.25/0.5/0.75Mg variants improve hardness up to 592 MPa. Ternary Al-9MM-2/4Ni display hypo-eutectic microstructures. Al-9MM-2Ni shows separated growth of Al<sub>11</sub>MM<sub>3</sub> and Al<sub>3</sub>Ni eutectic phases, while Al-9MM-4Ni features finely intertwined Al<sub>11</sub>MM<sub>3</sub>-Al<sub>3</sub>Ni fibers from co-solidification. The hyper-eutectic Al-9MM-5Ni contains primary Al<sub>3</sub>Ni particles alongside the intertwined fibers, raising the hardness to 739 MPa. Finally, quaternary Al-9MM-0.5/0.75Mg-4/4.5Ni alloys maintain hypo-eutectic microstructures with a significant increase of hardness to 929 MPa. The series Al-9MM, Al-9MM-0.75Mg, Al-9MM-4Ni, and Al-9MM-4.5Ni-0.75Mg exhibits increasing tensile yield strengths of 70, 83, 88, and 105 MPa, with decreasing ductility of 12.0, 5.8, 2.0, and 0.8 %. All Al-9MM-Mg-Ni alloys exhibit excellent hardness retention and coarsening resistance after thermal exposure at 300 or 350°C for up to 11 weeks. A machine-learning model accurately predicts the alloy's hardness evolution under thermal exposure. Feature analysis quantitively shows the strengthening impact of MM, Ni, and Mg addition and demonstrate enhanced strengthening retention, under thermal exposure, of Al<sub>11</sub>MM<sub>3</sub> over Al<sub>3</sub>Ni, alongside the beneficial effects of Mg homogenization. At 300 °C, Al-9MM-Mg-Ni alloys demonstrate higher creep resistance than most precipitation-strengthened Al-Sc-Zr-based alloys and solid-solution-strengthened Al-Mg alloys, with Al-9MM-4Ni as the best performer.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120452"},"PeriodicalIF":8.3,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142386156","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 : 2024-10-09DOI: 10.1016/j.actamat.2024.120453
Thomas Mann , Michael G. Fahrmann , Marisol Koslowski , Michael S. Titus
Density Functional Theory (DFT) calculations can determine planar defect energies and slip pathways that are present in ordered intermetallic systems used to strengthen Ni-based superalloys, but analytical models used to evaluate the strengthening effects of these phases often involve significant simplifying assumptions. Instead, Phase Field Dislocation Dynamics (PFDD) is a useful modeling tool that incorporates dislocation interactions with precipitates and slip pathways informed by DFT to determine how precipitate shearing might occur under applied stresses with improved accuracy over previous models. In this work, we apply PFDD to study precipitate shearing in HAYNES® 244®, a high strength Ni-based superalloy strengthened through a novel Ni2(Cr, Mo, W) phase that has a low symmetry Body Centered Orthorhombic (BCO) crystal structure which complicates analysis of slip pathways. Through our modeling, we show the formation of and evolution of extended dislocations in the matrix and in the precipitates, the interaction of dislocations with the precipitates, and the formation of planar faults in the precipitate. A key aspect of incorporating the DFT determined slip pathway is the influence of the unstable fault energy and the asymmetry of the energy pathway on the strengthening aspect of the precipitate. The resulting critical strengths are compared to analytical models. The size, orientation, particle distance, and calculated slip pathway for the different variants in this system are all shown to have an important effect on the critical stress to shear these precipitates.
{"title":"Phase field dislocation dynamics modeling of shearing modes in Ni2(Cr,Mo,W)-containing HAYNES® 244® Superalloy","authors":"Thomas Mann , Michael G. Fahrmann , Marisol Koslowski , Michael S. Titus","doi":"10.1016/j.actamat.2024.120453","DOIUrl":"10.1016/j.actamat.2024.120453","url":null,"abstract":"<div><div>Density Functional Theory (DFT) calculations can determine planar defect energies and slip pathways that are present in ordered intermetallic systems used to strengthen Ni-based superalloys, but analytical models used to evaluate the strengthening effects of these phases often involve significant simplifying assumptions. Instead, Phase Field Dislocation Dynamics (PFDD) is a useful modeling tool that incorporates dislocation interactions with precipitates and slip pathways informed by DFT to determine how precipitate shearing might occur under applied stresses with improved accuracy over previous models. In this work, we apply PFDD to study precipitate shearing in HAYNES® 244®, a high strength Ni-based superalloy strengthened through a novel Ni<sub>2</sub>(Cr, Mo, W) phase that has a low symmetry Body Centered Orthorhombic (BCO) crystal structure which complicates analysis of slip pathways. Through our modeling, we show the formation of and evolution of extended dislocations in the matrix and in the precipitates, the interaction of dislocations with the precipitates, and the formation of planar faults in the precipitate. A key aspect of incorporating the DFT determined slip pathway is the influence of the unstable fault energy and the asymmetry of the energy pathway on the strengthening aspect of the precipitate. The resulting critical strengths are compared to analytical models. The size, orientation, particle distance, and calculated slip pathway for the different variants in this system are all shown to have an important effect on the critical stress to shear these precipitates.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"281 ","pages":"Article 120453"},"PeriodicalIF":8.3,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142386177","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}
In this study, the γ’-V2O5 cathode material was prepared through a solution synthesis technique leading to homogeneous, fine and porous particles 100–200 nm in size. This successful preparation allows to overcome the huge drawback of the microsized material in terms of charge efficiency and to take benefit of the attractive Na insertion properties of γ’-V2O5, i. e. a significant available capacity of 145 mAh g- 1, a high working potential of about 3.25 V vs. Na+/Na, an excellent charge efficiency, a high-rate capability and good cycle life. A detailed structural study upon Na insertion/extraction shows that the proposed nanosizing approach promotes a homogeneous Na solubility and solid solution behavior in a wider composition range (0.4 < x ≤ 1 in γ-NaxV2O5) compared to the results previously reported for solid-state synthesized γ’-V2O5. Furthermore, highly reversible structural changes are evidenced. Key kinetic parameters governing the Na insertion-extraction reaction are discussed thanks to an impedance spectroscopy study revealing a faster Na diffusivity in the one-phase region. The obtained results allow a comprehensive understanding of the enhanced performance exhibited by the present sub-micronic γ’-V2O5 material.
在这项研究中，γ'-V2O5 阴极材料是通过溶液合成技术制备而成的，其颗粒均匀、细小且多孔，大小为 100-200 纳米。这种成功的制备方法克服了微型材料在充电效率方面的巨大缺陷，并利用了 γ'-V2O5 极具吸引力的 Na 插入特性，即 145 mAh g- 1 的显著可用容量、对 Na+/Na 约 3.25 V 的高工作电位、出色的充电效率、高速率能力和良好的循环寿命。对 Na 插入/萃取后的详细结构研究表明，与之前报道的固态合成γ'-V2O5 的结果相比，所提出的纳米化方法在更宽的成分范围（γ-NaxV2O5 中为 0.4 < x ≤ 1）内促进了均匀的 Na 溶解度和固溶行为。此外，还证明了高度可逆的结构变化。通过阻抗光谱研究发现，在单相区域，Na 的扩散速度更快，因此对 Na 插入萃取反应的关键动力学参数进行了讨论。所获得的结果有助于全面理解目前的亚微米级 γ'-V2O5 材料所表现出的更高性能。
{"title":"Unlocking the charge efficiency of γ’-V2O5 for Na-ion battery through a solution synthesis technique","authors":"Dauren Batyrbekuly , Barbara Laïk , Zhumabay Bakenov , Ankush Bhatia , Jean-Pierre Pereira-Ramos , Rita Baddour-Hadjean","doi":"10.1016/j.actamat.2024.120461","DOIUrl":"10.1016/j.actamat.2024.120461","url":null,"abstract":"<div><div>In this study, the γ’-V<sub>2</sub>O<sub>5</sub> cathode material was prepared through a solution synthesis technique leading to homogeneous, fine and porous particles 100–200 nm in size. This successful preparation allows to overcome the huge drawback of the microsized material in terms of charge efficiency and to take benefit of the attractive Na insertion properties of γ’-V<sub>2</sub>O<sub>5,</sub> i. e. a significant available capacity of 145 mAh g<sup>- 1</sup>, a high working potential of about 3.25 V vs. Na<sup>+</sup>/Na, an excellent charge efficiency, a high-rate capability and good cycle life. A detailed structural study upon Na insertion/extraction shows that the proposed nanosizing approach promotes a homogeneous Na solubility and solid solution behavior in a wider composition range (0.4 < <em>x</em> ≤ 1 in γ-Na<sub>x</sub>V<sub>2</sub>O<sub>5</sub>) compared to the results previously reported for solid-state synthesized γ’-V<sub>2</sub>O<sub>5</sub>. Furthermore, highly reversible structural changes are evidenced. Key kinetic parameters governing the Na insertion-extraction reaction are discussed thanks to an impedance spectroscopy study revealing a faster Na diffusivity in the one-phase region. The obtained results allow a comprehensive understanding of the enhanced performance exhibited by the present sub-micronic γ’-V<sub>2</sub>O<sub>5</sub> material.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120461"},"PeriodicalIF":8.3,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142386152","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 : 2024-10-09DOI: 10.1016/j.actamat.2024.120464
Zhengkai Wu , Shengchuan Wu , Jamie J. Kruzic , Yanan Hu , Huan Yu , Xingxing Zhang , Xiaopeng Li , Qingyuan Wang , Guozheng Kang , Philip J. Withers
Fish-scale-like melt pool structures and internal defects are characteristic features in additively manufactured (AM) metals. These play a critical role in the damage and fracture processes under different service loading conditions. However, the relationship between these damage features and loading conditions, as well as the spatial interactions between melt pool structures and internal defects remains poorly understood. Using in situ time-lapse synchrotron X-ray tomography and diffraction, we identify the initiation and growth events of life-limiting damage under tensile, low cycle fatigue (LCF), and high cycle fatigue (HCF) loading. A novel transition from meso-structure insensitive, defect-dominated short fatigue crack propagation to a meso-structure sensitive mechanism occurs as the plastic zone expands ahead of a growing crack from HCF to LCF to tensile loading. Under tension and LCF, the damage accumulation gradually increases and micro-voids nucleate at the melt pool boundaries (MPBs) after which the crack path follows the MPBs. In contrast, under HCF, surface defects initiate fatigue cracking and the MPBs have a very limited effect on the crack propagation path. Finally, a physics-informed machine learning method is introduced to develop a novel methodology for predicting fatigue life by including three-dimensional features of defects in AM parts.
鱼鳞状熔池结构和内部缺陷是快速成型（AM）金属的独特特征。这些特征在不同使用条件下的损伤和断裂过程中起着关键作用，并影响着材料的性能。然而，人们对这些损伤特征与加载条件之间的关系，以及熔池结构和内部缺陷之间的空间相互作用仍不甚了解。通过原位延时同步辐射 X 射线断层扫描和衍射，我们确定了在拉伸、低循环疲劳 (LCF) 和高循环疲劳 (HCF) 加载条件下寿命限制性损伤的起始和生长事件。随着不断增长的裂纹塑性区的扩大，出现了从对中观结构不敏感、以缺陷为主的短疲劳裂纹扩展到对中观结构敏感机制的新转变。在拉伸和低频条件下，损伤累积逐渐增加，微空洞在熔池边界（MPB）处成核，然后裂纹沿着 MPB 扩展。相反，在 HCF 条件下，表面缺陷会引发疲劳裂纹，而 MPB 对裂纹扩展路径的影响非常有限。最后，介绍了物理信息机器学习方法，通过纳入 AM 零件缺陷的三维特征，开发出一种预测疲劳寿命的新方法。
{"title":"Critical damage events of 3D printed AlSi10Mg alloy via in situ synchrotron X-ray tomography","authors":"Zhengkai Wu , Shengchuan Wu , Jamie J. Kruzic , Yanan Hu , Huan Yu , Xingxing Zhang , Xiaopeng Li , Qingyuan Wang , Guozheng Kang , Philip J. Withers","doi":"10.1016/j.actamat.2024.120464","DOIUrl":"10.1016/j.actamat.2024.120464","url":null,"abstract":"<div><div>Fish-scale-like melt pool structures and internal defects are characteristic features in additively manufactured (AM) metals. These play a critical role in the damage and fracture processes under different service loading conditions. However, the relationship between these damage features and loading conditions, as well as the spatial interactions between melt pool structures and internal defects remains poorly understood. Using <em>in situ</em> time-lapse synchrotron X-ray tomography and diffraction, we identify the initiation and growth events of life-limiting damage under tensile, low cycle fatigue (LCF), and high cycle fatigue (HCF) loading. A novel transition from meso-structure insensitive, defect-dominated short fatigue crack propagation to a meso-structure sensitive mechanism occurs as the plastic zone expands ahead of a growing crack from HCF to LCF to tensile loading. Under tension and LCF, the damage accumulation gradually increases and micro-voids nucleate at the melt pool boundaries (MPBs) after which the crack path follows the MPBs. In contrast, under HCF, surface defects initiate fatigue cracking and the MPBs have a very limited effect on the crack propagation path. Finally, a physics-informed machine learning method is introduced to develop a novel methodology for predicting fatigue life by including three-dimensional features of defects in AM parts.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120464"},"PeriodicalIF":8.3,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142386155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-08DOI: 10.1016/j.actamat.2024.120457
Yi Yao , Jonathan Cappola , Zhengyu Zhang , Qiang Zhu , Wenjun Cai , Xiaoxiang Yu , Lin Li
Refractory complex concentrated alloys (RCCAs) have emerged as a promising class of structural materials, demonstrating exceptional mechanical performance in aggressive environments. However, the complex atomic environments, significant lattice distortion, and vast compositional space of RCCAs present challenges to understanding the mechanisms that govern structure-property relationships. In this study, we explore the dislocation mechanisms in three model quaternary RCCAs, namely Mo25Nb10Ta25W40 (at. %), Mo25Nb25Ta25W25, and Mo25Nb40Ta25W10 using large-scale atomistic simulations and machine learning based Spectral Neighbor Analysis Potential. Our atomistic simulations examine how the chemical composition and local ordering influence the mobility of both edge and screw dislocations, and how lattice distortion and diffuse anti-phase boundary energy (DAPBE) affect dislocation behaviors during nanostructural evolution. Notably, with the increase in Nb concentration in the model RCCAs, both DAPBE and lattice distortion are simultaneously enhanced as the chemical short-range order (CSRO) evolves into nanoscale B2 precipitates. This evolution results in high lattice distortion due to the lattice mismatch between B2 precipitates and the random matrix. Consequently, B2 nanoprecipitates provide a stronger pinning effect, hindering edge dislocation motion while promoting cross-slip of screw dislocations, leading to a reduced screw-to-edge ratio in slip resistance and mobility discrepancy. These findings offer valuable insights into dislocation behaviors and interactions with ordered precipitates, highlighting the importance of exploring non-equiatomic compositions and advancing beyond CSRO in RCCAs. This study has implications for optimizing alloy compositions and processing methods for superior performance in aggressive environments.
{"title":"Nanostructure and dislocation interactions in refractory complex concentrated alloy: From chemical short-range order to nanoscale B2 precipitates","authors":"Yi Yao , Jonathan Cappola , Zhengyu Zhang , Qiang Zhu , Wenjun Cai , Xiaoxiang Yu , Lin Li","doi":"10.1016/j.actamat.2024.120457","DOIUrl":"10.1016/j.actamat.2024.120457","url":null,"abstract":"<div><div>Refractory complex concentrated alloys (RCCAs) have emerged as a promising class of structural materials, demonstrating exceptional mechanical performance in aggressive environments. However, the complex atomic environments, significant lattice distortion, and vast compositional space of RCCAs present challenges to understanding the mechanisms that govern structure-property relationships. In this study, we explore the dislocation mechanisms in three model quaternary RCCAs, namely Mo25Nb10Ta25W40 (at. %), Mo25Nb25Ta25W25, and Mo25Nb40Ta25W10 using large-scale atomistic simulations and machine learning based Spectral Neighbor Analysis Potential. Our atomistic simulations examine how the chemical composition and local ordering influence the mobility of both edge and screw dislocations, and how lattice distortion and diffuse anti-phase boundary energy (DAPBE) affect dislocation behaviors during nanostructural evolution. Notably, with the increase in Nb concentration in the model RCCAs, both DAPBE and lattice distortion are simultaneously enhanced as the chemical short-range order (CSRO) evolves into nanoscale B2 precipitates. This evolution results in high lattice distortion due to the lattice mismatch between B2 precipitates and the random matrix. Consequently, B2 nanoprecipitates provide a stronger pinning effect, hindering edge dislocation motion while promoting cross-slip of screw dislocations, leading to a reduced screw-to-edge ratio in slip resistance and mobility discrepancy. These findings offer valuable insights into dislocation behaviors and interactions with ordered precipitates, highlighting the importance of exploring non-equiatomic compositions and advancing beyond CSRO in RCCAs. This study has implications for optimizing alloy compositions and processing methods for superior performance in aggressive environments.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"281 ","pages":"Article 120457"},"PeriodicalIF":8.3,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142384923","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 : 2024-10-06DOI: 10.1016/j.actamat.2024.120454
Miao He , Yang Li , Bita Ghaffari , Yang Huo , Larry Godlewski , Mei Li , Yue Fan
Recent experiments have shown that Al-Si-Mg alloys solidified under high cooling rates may lead to the nucleation of Si-enriched clusters that are remarkably different from the conventional Mg-Si co-clusters (e.g. β″ particles), and yet the responsible mechanism remains to be elucidated. Here we tackle the problem using a multiscale modeling framework that integrates atomistic modeling, energy landscape sampling, and lattice-based kinetic Monte Carlo (kMC) simulation. The migration energy barriers for vacancy-mediated diffusion amid complex local chemical environments are predicted on-the-fly using a surrogate machine learning model. We discover that the actual vacancy-Si migration barriers are much lower than those assumed in the classic linear interpolation approximation. Such a strong deviation from conventional wisdom, in conjunction with differing Si solute composition, can lead to a great variety in the nucleated early-stage precipitates. More specifically, a high-level supersaturation of Si solute (i.e. ) would lead to an unexpectedly high enrichment of Si in the nucleated clusters with the Si:Mg ratio up to 5∼6; while at a lower-level supply of Si solute the Mg-Si co-clusters (i.e. Si:Mg ratio around 1∼2) are nucleated instead. These findings provide a viable explanation for the diverse types of early-stage precipitates observed in various experiments, from Si-enriched precipitates in high-pressure die cast Al alloys to β″ particles in conventional casting and/or heat-treated alloys. The implications of our findings are also discussed.
{"title":"Machine learning-augmented modeling on the formation of Si-dominated Non-β″ early-stage precipitates in Al-Si-Mg alloys with Si supersaturation induced by non-equilibrium solidification","authors":"Miao He , Yang Li , Bita Ghaffari , Yang Huo , Larry Godlewski , Mei Li , Yue Fan","doi":"10.1016/j.actamat.2024.120454","DOIUrl":"10.1016/j.actamat.2024.120454","url":null,"abstract":"<div><div>Recent experiments have shown that Al-Si-Mg alloys solidified under high cooling rates may lead to the nucleation of Si-enriched clusters that are remarkably different from the conventional Mg-Si co-clusters (<em>e.g. β″</em> particles), and yet the responsible mechanism remains to be elucidated. Here we tackle the problem using a multiscale modeling framework that integrates atomistic modeling, energy landscape sampling, and lattice-based kinetic Monte Carlo (kMC) simulation. The migration energy barriers for vacancy-mediated diffusion amid complex local chemical environments are predicted on-the-fly using a surrogate machine learning model. We discover that the actual vacancy-Si migration barriers are much lower than those assumed in the classic linear interpolation approximation. Such a strong deviation from conventional wisdom, in conjunction with differing Si solute composition, can lead to a great variety in the nucleated early-stage precipitates. More specifically, a high-level supersaturation of Si solute (<em>i.e.</em> <span><math><mrow><msub><mi>x</mi><mrow><mi>S</mi><mi>i</mi></mrow></msub><mo>/</mo><mrow><mo>(</mo><mrow><msub><mi>x</mi><mrow><mi>S</mi><mi>i</mi></mrow></msub><mo>+</mo><msub><mi>x</mi><mrow><mi>M</mi><mi>g</mi></mrow></msub></mrow><mo>)</mo></mrow><mo>></mo><mn>0.75</mn></mrow></math></span>) would lead to an unexpectedly high enrichment of Si in the nucleated clusters with the Si:Mg ratio up to 5∼6; while at a lower-level supply of Si solute the Mg-Si co-clusters (<em>i.e.</em> Si:Mg ratio around 1∼2) are nucleated instead. These findings provide a viable explanation for the diverse types of early-stage precipitates observed in various experiments, from Si-enriched precipitates in high-pressure die cast Al alloys to <em>β″</em> particles in conventional casting and/or heat-treated alloys. The implications of our findings are also discussed.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120454"},"PeriodicalIF":8.3,"publicationDate":"2024-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142379286","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 : 2024-10-05DOI: 10.1016/j.actamat.2024.120447
Qinsheng He , Tian-Yu Sun , Liang-Feng Huang
The continuous development of hydrogen-permeation barriers (HPB) based on metal nitrides highly desires a generic unification of the key thermodynamic and kinetic mechanisms therein. This work employs first-principles calculations to study the stability and diffusion trends of H impurity in the rock-salt, wurtzite, and sphalerite phases of the prototypical TiN and AlN. The formation energies () of H at various interstitial and vacant sites in these nitrides are calculated, and the underlying chemical-bonding and lattice-deformation mechanisms are self-consistently revealed by the systematic structual, energetic, and electronic-structure analyses. This leads to the discovery of a generic volcanic trend of in terms of the electron number on H (), which well portrays how the covalent-ionic H–N and H–metal bondings determine its stability in different atomistic environments. Then, the kinetic properties (e.g., potential barriers, diffusion coefficients, and isotope effects) of interstitial H in these nitrides are calculated, where the volcanic – relationship is applied to better understand the joint contributions of chemical bonding and lattice deformation. Finally, the revealed mechanisms and volcanic – relationship are generalized to successfully describe the behaviors of H in some important grain boundaries of c-TiN and c-AlN, including the twin frequently observed in c-TiN and the twin prototypical to many rock-salt materials. The widely varying hydrogen permeabilities measured in experiment on many nitride coatings are successfully explained, inspiring more useful chemical principles to guide the design of HPB coatings facing harsh environments with long-term reliability.
基于金属氮化物的渗氢屏障（HPB）的不断发展迫切需要对其中的关键热力学和动力学机制进行一般性的统一。本研究采用第一性原理计算方法，研究了 H 杂质在原型 TiN 和 AlN 的岩盐相、闪锌矿相和闪锌矿相中的稳定性和扩散趋势。通过系统的结构、能量和电子结构分析，计算了 H 在这些氮化物中不同间隙和空位的形成能 (Ef)，并自洽地揭示了潜在的化学键和晶格变形机制。这导致发现了以 H 上电子数（QH）表示的 Ef 的一般火山趋势，很好地描绘了共价离子 H-N 键和 H 金属键如何决定其在不同原子环境中的稳定性。然后，计算了这些氮化物中间隙 H 的动力学特性（如势垒、扩散系数和同位素效应），并应用火山 Ef-QH 关系来更好地理解化学键和晶格变形的共同作用。最后，将所揭示的机制和火山Ef-QH关系加以推广，成功地描述了氢在c-TiN和c-AlN的一些重要晶界中的行为，包括在c-TiN中经常观察到的Σ3{112}〈110〉孪晶和许多岩盐材料中典型的Σ5{210}〈001〉孪晶。我们成功地解释了实验中在许多氮化物涂层上测量到的差异很大的氢渗透率，从而启发了更有用的化学原理，以指导面对恶劣环境的高纯度氮化硼涂层的设计，并确保其长期可靠性。
{"title":"Chemical-bonding and lattice-deformation mechanisms unifying the stability and diffusion trends of hydrogen in TiN and AlN polymorphs","authors":"Qinsheng He , Tian-Yu Sun , Liang-Feng Huang","doi":"10.1016/j.actamat.2024.120447","DOIUrl":"10.1016/j.actamat.2024.120447","url":null,"abstract":"<div><div>The continuous development of hydrogen-permeation barriers (HPB) based on metal nitrides highly desires a generic unification of the key thermodynamic and kinetic mechanisms therein. This work employs first-principles calculations to study the stability and diffusion trends of H impurity in the rock-salt, wurtzite, and sphalerite phases of the prototypical TiN and AlN. The formation energies (<span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>f</mi></mrow></msub></math></span>) of H at various interstitial and vacant sites in these nitrides are calculated, and the underlying chemical-bonding and lattice-deformation mechanisms are self-consistently revealed by the systematic structual, energetic, and electronic-structure analyses. This leads to the discovery of a generic volcanic trend of <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>f</mi></mrow></msub></math></span> in terms of the electron number on H (<span><math><msub><mrow><mi>Q</mi></mrow><mrow><mi>H</mi></mrow></msub></math></span>), which well portrays how the covalent-ionic H–N and H–metal bondings determine its stability in different atomistic environments. Then, the kinetic properties (e.g., potential barriers, diffusion coefficients, and isotope effects) of interstitial H in these nitrides are calculated, where the volcanic <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>f</mi></mrow></msub></math></span>–<span><math><msub><mrow><mi>Q</mi></mrow><mrow><mi>H</mi></mrow></msub></math></span> relationship is applied to better understand the joint contributions of chemical bonding and lattice deformation. Finally, the revealed mechanisms and volcanic <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>f</mi></mrow></msub></math></span>–<span><math><msub><mrow><mi>Q</mi></mrow><mrow><mi>H</mi></mrow></msub></math></span> relationship are generalized to successfully describe the behaviors of H in some important grain boundaries of c-TiN and c-AlN, including the <span><math><mrow><mi>Σ</mi><mn>3</mn><mrow><mo>{</mo><mn>112</mn><mo>}</mo></mrow><mrow><mo>〈</mo><mn>110</mn><mo>〉</mo></mrow></mrow></math></span> twin frequently observed in c-TiN and the <span><math><mrow><mi>Σ</mi><mn>5</mn><mrow><mo>{</mo><mn>210</mn><mo>}</mo></mrow><mrow><mo>〈</mo><mn>001</mn><mo>〉</mo></mrow></mrow></math></span> twin prototypical to many rock-salt materials. The widely varying hydrogen permeabilities measured in experiment on many nitride coatings are successfully explained, inspiring more useful chemical principles to guide the design of HPB coatings facing harsh environments with long-term reliability.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"281 ","pages":"Article 120447"},"PeriodicalIF":8.3,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142377531","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 : 2024-10-04DOI: 10.1016/j.actamat.2024.120451
Dominique Chatain , Blandine Courtois , Saba Ahmad , Gerhard Dehm , Christina Scheu , Clémence Badie , Lionel Santinacci
Normal grain growth (NGG) of a (111) textured Ni film on c-sapphire and abnormal grain growth (AGG) of (100) grains at the expense of this (111) texture has been studied as a function of temperature with and without a capping layer. The grain boundaries (GBs) in the Ni film are controlled by the preferred orientation relationships (ORs) adopted by the Ni grains on the sapphire substrate. The 2 variants of a single OR, Ni(111)<>//Al2O3(0001)<>, form a (111) mazed bicrystal with Σ3 GBs. The (100) grains have a single OR, Ni(100)<010>//Al2O3(0001)<> with 3 variants; their GBs within the (111) grains have the (111)<>//(100)<010> misorientation.
(100) AGG within the (111) mazed bicrystal of the 100 nm Ni film takes place above 1023 K. The orientation transition is driven by the biaxial elastic modulus anisotropy which favors the growth of (100) grains over (111) grains, as this reduces the elastic strain energy induced by the thermal mismatch between Ni and sapphire. (100) AGG is suppressed and the NGG of the (111) texture is slowed down when the film is covered by a 10 nm amorphous alumina layer aimed at inhibiting surface diffusion. Thus, it is proposed that as long as the surface can act as a sink for the point defects diffusing along the GBs, the movement of the GBs is correlated to the diffusivity of atoms and vacancies, which is a function of their misorientation and crystallographic GB structure.
{"title":"A potential mechanism for abnormal grain growth in Ni thin films on c-sapphire","authors":"Dominique Chatain , Blandine Courtois , Saba Ahmad , Gerhard Dehm , Christina Scheu , Clémence Badie , Lionel Santinacci","doi":"10.1016/j.actamat.2024.120451","DOIUrl":"10.1016/j.actamat.2024.120451","url":null,"abstract":"<div><div>Normal grain growth (NGG) of a (111) textured Ni film on c-sapphire and abnormal grain growth (AGG) of (100) grains at the expense of this (111) texture has been studied as a function of temperature with and without a capping layer. The grain boundaries (GBs) in the Ni film are controlled by the preferred orientation relationships (ORs) adopted by the Ni grains on the sapphire substrate. The 2 variants of a single OR, Ni(111)<<span><math><mrow><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>0</mn></mrow></math></span>>//Al<sub>2</sub>O<sub>3</sub>(0001)<<span><math><mrow><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>00</mn></mrow></math></span>>, form a (111) mazed bicrystal with Σ3 GBs. The (100) grains have a single OR, Ni(100)<010>//Al<sub>2</sub>O<sub>3</sub>(0001)<<span><math><mrow><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>00</mn></mrow></math></span>> with 3 variants; their GBs within the (111) grains have the (111)<<span><math><mrow><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>0</mn></mrow></math></span>>//(100)<010> misorientation.</div><div>(100) AGG within the (111) mazed bicrystal of the 100 nm Ni film takes place above 1023 K. The orientation transition is driven by the biaxial elastic modulus anisotropy which favors the growth of (100) grains over (111) grains, as this reduces the elastic strain energy induced by the thermal mismatch between Ni and sapphire. (100) AGG is suppressed and the NGG of the (111) texture is slowed down when the film is covered by a 10 nm amorphous alumina layer aimed at inhibiting surface diffusion. Thus, it is proposed that as long as the surface can act as a sink for the point defects diffusing along the GBs, the movement of the GBs is correlated to the diffusivity of atoms and vacancies, which is a function of their misorientation and crystallographic GB structure.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"281 ","pages":"Article 120451"},"PeriodicalIF":8.3,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142374060","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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