Pub Date : 2024-10-19DOI: 10.1016/j.actamat.2024.120462
{"title":"Recipients of the 2023 Acta Materialia, inc. student awards","authors":"","doi":"10.1016/j.actamat.2024.120462","DOIUrl":"10.1016/j.actamat.2024.120462","url":null,"abstract":"","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120462"},"PeriodicalIF":8.3,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142450116","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 : 2024-10-19DOI: 10.1016/j.actamat.2024.120445
Yongqing Chen , Yuan Ma , Jin Zhou , Binglu Zhang , Yuyang Wang , Bin Li , Lifei Wang , Lijie Qiao , Luning Wang , Tao Guo , Yang He
Twinning is an essential deformation mode of crystals which is attracting growing attention due to its potential in simultaneously improve the strength and ductility of metals. It is generally believed that twinning is mediated by shear and atomic shuffles on an invariant twinning plane. Here, by using in situ high resolution transmission electron microscopy, we report on an extension twinning mode in rhenium nanocrystals along the direction on the plane, which can be mediated by the formation of interfacial defects that fall between the parent prismatic plane and the twin pyramidal plane which are a pair of corresponding planes of the twinning mode. The incoherent twin boundary can partly evolve into the coherent twinning plane during detwinning. The findings provide direct evidences to the twin in hexagonal close-packed metals and corroborate the conjecture that twinning nucleation is essentially a transformation that conforms to and establishes the lattice correspondence which can be mediated by interfacial processes other than homogeneous shear on the twinning plane.
{"title":"{202¯1} Twinning in hexagonal close-packed Re nanocrystals mediated by {101¯1}|{101¯0} interfacial facets","authors":"Yongqing Chen , Yuan Ma , Jin Zhou , Binglu Zhang , Yuyang Wang , Bin Li , Lifei Wang , Lijie Qiao , Luning Wang , Tao Guo , Yang He","doi":"10.1016/j.actamat.2024.120445","DOIUrl":"10.1016/j.actamat.2024.120445","url":null,"abstract":"<div><div>Twinning is an essential deformation mode of crystals which is attracting growing attention due to its potential in simultaneously improve the strength and ductility of metals. It is generally believed that twinning is mediated by shear and atomic shuffles on an invariant twinning plane. Here, by using in situ high resolution transmission electron microscopy, we report on an extension twinning mode in rhenium nanocrystals along the <span><math><mrow><mo>〈</mo><mn>10</mn><mover><mrow><mn>1</mn></mrow><mo>‾</mo></mover><mover><mrow><mn>4</mn></mrow><mo>‾</mo></mover><mo>〉</mo></mrow></math></span> direction on the <span><math><mrow><mo>{</mo><mn>20</mn><mover><mrow><mn>2</mn></mrow><mo>‾</mo></mover><mn>1</mn><mo>}</mo></mrow></math></span> plane, which can be mediated by the formation of interfacial defects that fall between the parent prismatic plane and the twin pyramidal plane which are a pair of corresponding planes of the <span><math><mrow><mo>{</mo><mrow><mn>20</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>1</mn></mrow><mo>}</mo></mrow></math></span> twinning mode. The incoherent twin boundary can partly evolve into the coherent twinning plane during detwinning. The findings provide direct evidences to the <span><math><mrow><mo>{</mo><mrow><mn>20</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>1</mn></mrow><mo>}</mo></mrow></math></span> twin in hexagonal close-packed metals and corroborate the conjecture that twinning nucleation is essentially a transformation that conforms to and establishes the lattice correspondence which can be mediated by interfacial processes other than homogeneous shear on the twinning plane.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120445"},"PeriodicalIF":8.3,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142450141","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 : 2024-10-18DOI: 10.1016/j.actamat.2024.120492
Chaoqun Zhu , Zhuang Liu , Hubin Luo , Haichen Wu , Guoxin Chen , Yang Yang , Yu Liu , Dongliang Tan , Yaowen Li , Rui Xia , Renjie Chen , Aru Yan
The coercivity of 2:17-type SmCo magnets is mainly determined by the gradient distribution of Cu within the cell boundary phase. However, the fundamental migratory behavior and driving force causing such Cu distribution remains unclear. In this work, the phenomenon of Cu enrichment at the lamellar/intracellular interface is reported at the atomic scale, and a new Cu diffusion mechanism of 2:17-type SmCo magnets is proposed via combining microstructure characterization with first-principles calculation. Our study indicates that Cu will migrate from the intracellular phase to the lamellar/intracellular phase interface following the migration of twin boundary, and then diffuses further along the lamellar phase interface to the cell boundary, achieving the expected Cu-rich cell boundary structure. Doping Pr results in a reduction of Cu substitution energy in the lamellar phase, leading to a decreased driving force during the subsequent Cu diffusion. As a result, the Cu does not completely diffuse into the cell boundary phase there is Cu enrichment at the interface between lamellar and intracellular phases. The Cu concentration of the cell boundaries could be increased in 2:17-type SmCo magnets by reasonable designing the substitution energy difference of intracellular phase, lamellar phase and cell boundary phase that promote Cu diffusion to cell boundary. Our study sheds light on the control of Cu segregation in magnets and a new strategy for enhancing the magnetic performance of 2:17-type SmCo magnets.
{"title":"Atomic-scale revelation of Cu diffusion mechanism in high-performance Pr-doped 2:17-type SmCo magnets","authors":"Chaoqun Zhu , Zhuang Liu , Hubin Luo , Haichen Wu , Guoxin Chen , Yang Yang , Yu Liu , Dongliang Tan , Yaowen Li , Rui Xia , Renjie Chen , Aru Yan","doi":"10.1016/j.actamat.2024.120492","DOIUrl":"10.1016/j.actamat.2024.120492","url":null,"abstract":"<div><div>The coercivity of 2:17-type SmCo magnets is mainly determined by the gradient distribution of Cu within the cell boundary phase. However, the fundamental migratory behavior and driving force causing such Cu distribution remains unclear. In this work, the phenomenon of Cu enrichment at the lamellar/intracellular interface is reported at the atomic scale, and a new Cu diffusion mechanism of 2:17-type SmCo magnets is proposed via combining microstructure characterization with first-principles calculation. Our study indicates that Cu will migrate from the intracellular phase to the lamellar/intracellular phase interface following the migration of twin boundary, and then diffuses further along the lamellar phase interface to the cell boundary, achieving the expected Cu-rich cell boundary structure. Doping Pr results in a reduction of Cu substitution energy in the lamellar phase, leading to a decreased driving force during the subsequent Cu diffusion. As a result, the Cu does not completely diffuse into the cell boundary phase there is Cu enrichment at the interface between lamellar and intracellular phases. The Cu concentration of the cell boundaries could be increased in 2:17-type SmCo magnets by reasonable designing the substitution energy difference of intracellular phase, lamellar phase and cell boundary phase that promote Cu diffusion to cell boundary. Our study sheds light on the control of Cu segregation in magnets and a new strategy for enhancing the magnetic performance of 2:17-type SmCo magnets.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120492"},"PeriodicalIF":8.3,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554648","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 : 2024-10-18DOI: 10.1016/j.actamat.2024.120488
Antonio Carlos de F. Silveira , Lisa T. Belkacemi , Pedro José de Castro , Marco Schowalter , Rainer Fechte-Heinen , Jérémy Epp
Additively manufactured components are generally heat treated to remove the undesired microstructure formed during the repeated heating-cooling cycles inherent to the process, known as intrinsic heat treatment (IHT). Recently, the IHT has been explored as a driving force for precipitation hardening in steels which can potentially shorten the manufacturing chain of AM components. However, the mechanisms behind the formation of secondary phase precipitates during the complex thermal history remains unclear. In this work, a combination of in situ high energy X-ray diffraction, atom probe tomography, scanning and transmission electron microscopy were used to reveal the precipitation sequence in an X40CrMoV5–1 tool steel during laser-directed energy deposition (L-DED). V-rich MCN and V8CN7 carbonitrides, as well as, Fe-Cr-rich M3C and M7C3 carbides were formed at different stages of the L-DED. Their evolution and resulting chemical stoichiometry was correlated to the exact phase transformation occurring in the microstructure during the IHT over different regions along the built direction. Finally, the combined results from the in situ and ex situ experiments enabled us to retrace the history of the full microstructure during the L-DED process. The findings lead to the conclusion that secondary hardening effect in tool steel is, as expected, sensitive to the severity of the IHT, and if limited, can result in a tempered microstructure comparable to the ones conventionally obtained after tempering heat treatments.
增材制造部件一般都要经过热处理，以去除在该工艺固有的反复加热-冷却循环过程中形成的不良微观结构，即所谓的固有热处理（IHT）。最近，本征热处理被认为是钢材沉淀硬化的一种驱动力，有可能缩短 AM 组件的制造链。然而，在复杂的热历史过程中形成次生相析出物的机制仍不清楚。在这项工作中，我们结合使用了原位高能 X 射线衍射、原子探针断层扫描、扫描和透射电子显微镜来揭示 X40CrMoV5-1 工具钢在激光能量沉积（L-DED）过程中的析出序列。在 L-DED 的不同阶段形成了富含 V 的 MCN 和 V8CN7 碳氮化物，以及富含 Fe-Cr 的 M3C 和 M7C3 碳化物。它们的演变和由此产生的化学计量学与沿建造方向不同区域的 IHT 期间微观结构中发生的确切相变相关联。最后，综合原位和非原位实验的结果，我们得以回溯 L-DED 过程中整个微观结构的历史。研究结果得出的结论是，工具钢中的二次硬化效应正如预期的那样，对 IHT 的严重程度非常敏感，如果受到限制，可以产生与传统回火热处理后获得的回火微观结构相当的微观结构。
{"title":"Effect of intrinsic heat treatment on the precipitate formation of X40CrMoV5–1 tool steel during laser-directed energy deposition: A coupled study of atom probe tomography and in situ synchrotron X-ray diffraction","authors":"Antonio Carlos de F. Silveira , Lisa T. Belkacemi , Pedro José de Castro , Marco Schowalter , Rainer Fechte-Heinen , Jérémy Epp","doi":"10.1016/j.actamat.2024.120488","DOIUrl":"10.1016/j.actamat.2024.120488","url":null,"abstract":"<div><div>Additively manufactured components are generally heat treated to remove the undesired microstructure formed during the repeated heating-cooling cycles inherent to the process, known as intrinsic heat treatment (IHT). Recently, the IHT has been explored as a driving force for precipitation hardening in steels which can potentially shorten the manufacturing chain of AM components. However, the mechanisms behind the formation of secondary phase precipitates during the complex thermal history remains unclear. In this work, a combination of <em>in situ</em> high energy X-ray diffraction, atom probe tomography, scanning and transmission electron microscopy were used to reveal the precipitation sequence in an X40CrMoV5–1 tool steel during laser-directed energy deposition (L-DED). V-rich MCN and V<sub>8</sub>CN<sub>7</sub> carbonitrides, as well as, Fe-Cr-rich M<sub>3</sub>C and M<sub>7</sub>C<sub>3</sub> carbides were formed at different stages of the L-DED. Their evolution and resulting chemical stoichiometry was correlated to the exact phase transformation occurring in the microstructure during the IHT over different regions along the built direction. Finally, the combined results from the <em>in situ</em> and <em>ex situ</em> experiments enabled us to retrace the history of the full microstructure during the L-DED process. The findings lead to the conclusion that secondary hardening effect in tool steel is, as expected, sensitive to the severity of the IHT, and if limited, can result in a tempered microstructure comparable to the ones conventionally obtained after tempering heat treatments.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120488"},"PeriodicalIF":8.3,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593242","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 : 2024-10-18DOI: 10.1016/j.actamat.2024.120491
Pierfrancesco Maltoni , Gianni Barucca , Bogdan Rutkowski , Sergey A. Ivanov , Nader Yaacoub , Anastasiia Mikheenkova , Gustav Ek , Mirva Eriksson , Bjarne Almqvist , Marianna Vasilakaki , Gaspare Varvaro , Tapati Sarkar , José A. De Toro , Kalliopi Trohidou , Davide Peddis , Roland Mathieu
We have investigated the bottom-up sol-gel synthesis of nanocomposite powders comprising two magnetic phases (hexagonal Sr ferrite and spinel Co ferrite) in order to outline a strategy to obtain permanent magnets with large coercivities via low-cost and scalable syntheses. The correlation between morphological, structural and macroscopic magnetic properties of Al-substituted SrFe12O19 and SrFe12O19/CoFe2O4 nanocomposites was analyzed in detail. The hysteretic behavior can be tuned by cation substitution and/or modulation of the super-exchange coupling at the interface of the constituting phases. The magnetic data, supported by Monte Carlo simulations, indicates enhanced magnetic coupling within the composite: this observation underscores the significance of soft crystallite size and epitaxial growth quality at the interface as key factors influencing super-exchange coupling strength, ranging from fully coupled to essentially decoupled composites. Bulk magnets with high density were manufactured by compacting these nanostructured phases using spark plasma sintering, without an applied magnetic field. Consolidation of powders significantly impacted magnetic properties, by increasing remanent magnetization and decreasing coercivity due to enhanced super-exchange coupling. The presence of two phases hindered reciprocal growth, influencing coercivity differently in various compositions. Overall, the compaction enhanced magnet performance through improved particle alignment and super-exchange coupling, offering the potential for optimized magnet design.
我们研究了由两种磁性相（六方态 Sr 铁氧体和尖晶石态 Co 铁氧体）组成的纳米复合粉末的自下而上溶胶-凝胶合成，从而勾勒出一种通过低成本和可扩展合成获得大矫顽力永磁体的策略。详细分析了铝取代的 SrFe12O19 和 SrFe12O19/CoFe2O4 纳米复合材料的形态、结构和宏观磁性能之间的相关性。滞后行为可通过阳离子替代和/或构成相界面上的超交换耦合调节。蒙特卡洛模拟支持的磁性数据表明，复合材料内部的磁耦合增强了：这一观察结果强调了界面处软晶体尺寸和外延生长质量的重要性，它们是影响超交换耦合强度的关键因素。在没有外加磁场的情况下，利用火花等离子烧结压实这些纳米结构相，制造出了高密度的块状磁体。由于超交换耦合增强，粉末的固结会增加剩磁，降低矫顽力，从而对磁性能产生重大影响。两相的存在阻碍了互生，对不同成分的矫顽力产生了不同的影响。总之，压实通过改善颗粒排列和超交换耦合提高了磁体性能，为优化磁体设计提供了可能。
{"title":"Engineering hard ferrite composites by combining nanostructuring and Al3+ Substitution: From nano to dense bulk magnets","authors":"Pierfrancesco Maltoni , Gianni Barucca , Bogdan Rutkowski , Sergey A. Ivanov , Nader Yaacoub , Anastasiia Mikheenkova , Gustav Ek , Mirva Eriksson , Bjarne Almqvist , Marianna Vasilakaki , Gaspare Varvaro , Tapati Sarkar , José A. De Toro , Kalliopi Trohidou , Davide Peddis , Roland Mathieu","doi":"10.1016/j.actamat.2024.120491","DOIUrl":"10.1016/j.actamat.2024.120491","url":null,"abstract":"<div><div>We have investigated the bottom-up sol-gel synthesis of nanocomposite powders comprising two magnetic phases (hexagonal Sr ferrite and spinel Co ferrite) in order to outline a strategy to obtain permanent magnets with large coercivities via low-cost and scalable syntheses. The correlation between morphological, structural and macroscopic magnetic properties of Al-substituted SrFe<sub>12</sub>O<sub>19</sub> and SrFe<sub>12</sub>O<sub>19</sub>/CoFe<sub>2</sub>O<sub>4</sub> nanocomposites was analyzed in detail. The hysteretic behavior can be tuned by cation substitution and/or modulation of the super-exchange coupling at the interface of the constituting phases. The magnetic data, supported by Monte Carlo simulations, indicates enhanced magnetic coupling within the composite: this observation underscores the significance of soft crystallite size and epitaxial growth quality at the interface as key factors influencing super-exchange coupling strength, ranging from fully coupled to essentially decoupled composites. Bulk magnets with high density were manufactured by compacting these nanostructured phases using spark plasma sintering, without an applied magnetic field. Consolidation of powders significantly impacted magnetic properties, by increasing remanent magnetization and decreasing coercivity due to enhanced super-exchange coupling. The presence of two phases hindered reciprocal growth, influencing coercivity differently in various compositions. Overall, the compaction enhanced magnet performance through improved particle alignment and super-exchange coupling, offering the potential for optimized magnet design.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120491"},"PeriodicalIF":8.3,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571641","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 : 2024-10-18DOI: 10.1016/j.actamat.2024.120472
Olga Guseva, Patrik Schmutz, Lars P.H. Jeurgens
Fundamental understanding of the phase stability of oxides in aqueous environments is of eminent importance for a broad range of disciplines, such as corrosion, tribology, catalysis, medical implants, biosensing and environmental sciences. Most oxide-to-hydroxide phase transformation sequences proceed by consecutive formation of different metastable hydroxide phases towards the most stable bulk hydroxide phase, in accord with Ostwald's Rule of Stages and thus in contradiction with bulk thermodynamics. In this work, a novel unified thermodynamic model is presented for predicting such metastable oxide-to-hydroxide phase transformation sequences by accounting for the energy barrier(s) associated with the creation of new interface(s) between the competing parent and product phase(s). To this end, semi-empirical expressions for the estimation of the interface energies between metals, oxides and/or hydroxides were derived based on the macroscopic atom approach. Application of the model to the phase stability of aluminium in water (at neutral pH) for 298 ≤ T ≤ 500 K predicts a solid-state phase transformation sequence from Al → am-Al2O3 → (pseudo)boehmite, in accord with experimental observations. Subsequent competing formation of the trihydroxide phases bayerite and gibbsite by a dissolution-precipitation on the (pseudo)boehmite surface is equally favoured and critically depends on the hydrolysis of dissolved Al3+ species in solution, as governed by e.g. pH, temperature and the presence of foreign ions in solution.
从根本上了解氧化物在水环境中的相稳定性，对于腐蚀、摩擦学、催化、医疗植入、生物传感和环境科学等众多学科都非常重要。大多数氧化物到氢氧化物的相变顺序都是通过连续形成不同的可褪色氢氧化物相，最终形成最稳定的主体氢氧化物相，这符合奥斯特瓦尔德阶段法则，因此与主体热力学相矛盾。本研究提出了一个新颖的统一热力学模型，通过考虑在相互竞争的母相和产物相之间建立新界面所产生的能量障碍，预测这种可褪色氧化物到氢氧化物的相变顺序。为此，基于宏观原子方法，推导出了估算金属、氧化物和/或氢氧化物之间界面能量的半经验表达式。将该模型应用于 298 ≤ T ≤ 500 K 时铝在水（中性 pH 值）中的相稳定性，预测了铝 → am-Al2O3 → （伪）玻镁铁的固态相变序列，与实验观察结果一致。随后在（伪）波长石表面通过溶解-沉淀作用竞争形成的三氢氧化物相贝叶石和吉布斯特同样有利，并且关键取决于溶液中溶解的 Al3+ 物种的水解作用，例如 pH 值、温度和溶液中外来离子的存在。
{"title":"Predicting metastable oxide-to-hydroxide phase transformations by bulk and interface thermodynamics: Application to the phase stability of aluminium oxides and hydroxides in water","authors":"Olga Guseva, Patrik Schmutz, Lars P.H. Jeurgens","doi":"10.1016/j.actamat.2024.120472","DOIUrl":"10.1016/j.actamat.2024.120472","url":null,"abstract":"<div><div>Fundamental understanding of the phase stability of oxides in aqueous environments is of eminent importance for a broad range of disciplines, such as corrosion, tribology, catalysis, medical implants, biosensing and environmental sciences. Most oxide-to-hydroxide phase transformation sequences proceed by consecutive formation of different metastable hydroxide phases towards the most stable bulk hydroxide phase, in accord with Ostwald's Rule of Stages and thus in contradiction with bulk thermodynamics. In this work, a novel unified thermodynamic model is presented for predicting such metastable oxide-to-hydroxide phase transformation sequences by accounting for the energy barrier(s) associated with the creation of new interface(s) between the competing parent and product phase(s). To this end, semi-empirical expressions for the estimation of the interface energies between metals, oxides and/or hydroxides were derived based on the macroscopic atom approach. Application of the model to the phase stability of aluminium in water (at neutral pH) for 298 ≤ <em>T</em> ≤ 500 K predicts a solid-state phase transformation sequence from Al → <em>am-</em>Al<sub>2</sub>O<sub>3</sub> → (pseudo)boehmite, in accord with experimental observations. Subsequent competing formation of the trihydroxide phases bayerite and gibbsite by a dissolution-precipitation on the (pseudo)boehmite surface is equally favoured and critically depends on the hydrolysis of dissolved Al<sup>3+</sup> species in solution, as governed by e.g. pH, temperature and the presence of foreign ions in solution.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120472"},"PeriodicalIF":8.3,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142657502","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 : 2024-10-16DOI: 10.1016/j.actamat.2024.120480
Yuyang Wang, Bin Li, Yiliang Liao
Twin nucleation in high symmetry cubic structures is closely related to the activities of dissociated lattice dislocations. However, in low symmetry hexagonal close-packed (HCP) metals, the nucleation mechanisms for deformation twinning remain largely unclear. In this work, we conduct atomistic simulations and uncover a new mechanism for nucleation of twinning which is an important mode in some HCP metals such as titanium and zirconium. Our simulations show that a coherent twin boundary can be formed as a result of twin-twin interaction between co-zone twin variants. During deformation, three co-zone twins form first and then interact. Two of the twin boundaries (TBs) merge into a coherent TB. This nucleation process does not involve any lattice dislocations or twinning dislocations. Lattice correspondence analyses indicate that such a nucleation process is feasible because all these and twins have the same (0001) K2 plane. The migration of TB is found to be mediated by the single-layer twinning dislocations.
{"title":"A new mechanism for nucleation of {112¯2}〈112¯3¯〉 twinning via interaction of {112¯1}〈112¯6¯〉 twin variants in hexagonal close-packed metals","authors":"Yuyang Wang, Bin Li, Yiliang Liao","doi":"10.1016/j.actamat.2024.120480","DOIUrl":"10.1016/j.actamat.2024.120480","url":null,"abstract":"<div><div>Twin nucleation in high symmetry cubic structures is closely related to the activities of dissociated lattice dislocations. However, in low symmetry hexagonal close-packed (HCP) metals, the nucleation mechanisms for deformation twinning remain largely unclear. In this work, we conduct atomistic simulations and uncover a new mechanism for nucleation of <span><math><mrow><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo></mrow><mrow><mo>〈</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mover><mn>3</mn><mo>¯</mo></mover></mrow><mo>〉</mo></mrow></mrow></math></span> twinning which is an important mode in some HCP metals such as titanium and zirconium. Our simulations show that a coherent <span><math><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo></mrow></math></span> twin boundary can be formed as a result of twin-twin interaction between co-zone <span><math><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>1</mn></mrow><mo>}</mo></mrow></math></span> twin variants. During deformation, three co-zone <span><math><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>1</mn></mrow><mo>}</mo></mrow></math></span> twins form first and then interact. Two of the <span><math><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>1</mn></mrow><mo>}</mo></mrow></math></span> twin boundaries (TBs) merge into a coherent <span><math><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo></mrow></math></span> TB. This nucleation process does not involve any lattice dislocations or twinning dislocations. Lattice correspondence analyses indicate that such a nucleation process is feasible because all these <span><math><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>1</mn></mrow><mo>}</mo></mrow></math></span> and <span><math><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo></mrow></math></span> twins have the same (0001) K<sub>2</sub> plane. The migration of <span><math><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo></mrow></math></span> TB is found to be mediated by the single-layer twinning dislocations.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120480"},"PeriodicalIF":8.3,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142439949","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 : 2024-10-16DOI: 10.1016/j.actamat.2024.120479
Andrey Orekhov , Nicolas Gauquelin , Guillaume Kermouche , Alejandro Gomez-Perez , Paul Baral , Ralf Dohmen , Michaël Coulombier , Johan Verbeeck , Jean Pierre Raskin , Thomas Pardoen , Dominique Schryvers , Jun Lin , Patrick Cordier , Hosni Idrissi
The mechanical properties of amorphous olivine (a-olivine) deformed at room temperature are investigated in situ in a TEM under uniaxial tension using a Push-to-Pull (PTP) device. Thin films of a-olivine were produced by pulsed laser deposition (PLD). With or without electron irradiation, a-olivine films deform plastically, with a gradual transition that makes impossible the determination of a precise threshold. The strength attains values up to 2.5 GPa. The increasing strain-rate in load control results in an apparent softening with stress drop. The fracture strain reaches values close to 30 % without e-beam irradiation. Under electron illumination at 200 kV, the strength is lower, around 1.7 GPa, while higher elongations close to 36 % are obtained. Alternating beam-off and beam-on sequences lead to exceptionally large fracture strains equal to 68 % at 200 kV and 139 % at 80 kV. EELS measurements were performed to characterize the interaction between the electron beam and a-olivine. At a voltage of 80 kV, radiolysis accompanied by oxygen release dominates whereas at high voltage (300 kV) the interaction is dominated by knock-on type defects. Radiolysis is also the main interaction mechanism at 200 kV with low exposition which corresponds to most of our in situ TEM deformation experiments. To interpret the mechanical data, a simple 1D model has been developed to rationalize the load transfer between the PTP device and the specimen. The strain-rate sensitivity is 6 to 10 times higher when a-olivine is deformed under electron irradiation.
{"title":"Room temperature electron beam sensitive viscoplastic response of ultra-ductile amorphous olivine films","authors":"Andrey Orekhov , Nicolas Gauquelin , Guillaume Kermouche , Alejandro Gomez-Perez , Paul Baral , Ralf Dohmen , Michaël Coulombier , Johan Verbeeck , Jean Pierre Raskin , Thomas Pardoen , Dominique Schryvers , Jun Lin , Patrick Cordier , Hosni Idrissi","doi":"10.1016/j.actamat.2024.120479","DOIUrl":"10.1016/j.actamat.2024.120479","url":null,"abstract":"<div><div>The mechanical properties of amorphous olivine (a-olivine) deformed at room temperature are investigated <em>in situ</em> in a TEM under uniaxial tension using a Push-to-Pull (PTP) device. Thin films of a-olivine were produced by pulsed laser deposition (PLD). With or without electron irradiation, a-olivine films deform plastically, with a gradual transition that makes impossible the determination of a precise threshold. The strength attains values up to 2.5 GPa. The increasing strain-rate in load control results in an apparent softening with stress drop. The fracture strain reaches values close to 30 % without e-beam irradiation. Under electron illumination at 200 kV, the strength is lower, around 1.7 GPa, while higher elongations close to 36 % are obtained. Alternating beam-off and beam-on sequences lead to exceptionally large fracture strains equal to 68 % at 200 kV and 139 % at 80 kV. EELS measurements were performed to characterize the interaction between the electron beam and a-olivine. At a voltage of 80 kV, radiolysis accompanied by oxygen release dominates whereas at high voltage (300 kV) the interaction is dominated by knock-on type defects. Radiolysis is also the main interaction mechanism at 200 kV with low exposition which corresponds to most of our <em>in situ</em> TEM deformation experiments. To interpret the mechanical data, a simple 1D model has been developed to rationalize the load transfer between the PTP device and the specimen. The strain-rate sensitivity is 6 to 10 times higher when a-olivine is deformed under electron irradiation.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120479"},"PeriodicalIF":8.3,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142439581","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 : 2024-10-15DOI: 10.1016/j.actamat.2024.120460
Benedikt Beckmann , Andreas Taubel , Tino Gottschall , Lukas Pfeuffer , David Koch , Franziska Staab , Enrico Bruder , Franziska Scheibel , Konstantin P. Skokov , Oliver Gutfleisch
Ni-Co-Mn-Ti all-d Heusler alloys are attracting considerable attention for solid-state caloric cooling applications due to their promising combination of excellent caloric and mechanical properties. Here, we report on the maximum attainable magnetocaloric effect in Ni37Co13Mn34.5Ti15.5, which shows a first-order magnetostructural martensitic transformation around room temperature. Heat capacity measurements reveal a giant transition entropy change of 43.5 J(kgK)protect relax special {t4ht=−}1 and are utilized to estimate the magnetocaloric effect as well as the magnetic fields required to saturate it in isothermal and adiabatic conditions. Confirming the results based on this approach, we achieve maximum isothermal entropy changes and directly measured adiabatic temperature changes of 37.8 J(kgK)protect relax special {t4ht=−}1 and 20.2 K, respectively. Thus, the herein reported maximum attainable magnetocaloric effect outperforms classical Ni-Mn-based Heusler alloys, such as Ni(-Co)-Mn-In. Especially the saturated adiabatic temperature change surpasses all previously published values of magnetic field-induced first-order phase transitions measured around room temperature in pulsed magnetic fields in recent years. Thereby, we demonstrate that Ni(-Co)-Mn-Ti Heusler alloys are particularly suitable for the application of sufficiently large external stimuli to fully induce the phase transition and exploit their intrinsically large caloric effect.
镍-钴-锰-钛全二元 Heusler 合金由于兼具出色的热性能和机械性能，在固态热冷却应用中备受关注。在此，我们报告了 Ni37Co13Mn34.5Ti15.5 中可达到的最大磁致冷效应，它在室温附近显示出一阶磁致结构马氏体转变。热容量测量显示了43.5 J(kgK)protect relax special {t4ht=-}1的巨大转变熵变，并利用它来估算磁致效应以及在等温和绝热条件下使其饱和所需的磁场。基于这种方法的结果得到了证实，我们获得的最大等温熵变和直接测量的绝热温度变化分别为 37.8 J（kgK）protect relax special {t4ht=-}1 和 -20.2 K。因此，本文所报告的可达到的最大磁致效应优于经典的镍锰基海斯勒合金，如镍（-Co）-锰-铟。尤其是饱和绝热温度变化超过了近年来在脉冲磁场中室温附近测量到的所有已公布的磁场诱导一阶相变值。因此，我们证明了 Ni（-Co）-Mn-Ti Heusler 合金特别适合应用足够大的外部刺激来充分诱导相变并利用其内在的大热效应。
{"title":"Giant magnetocaloric effect of Ni-Co-Mn-Ti all-d Heusler alloys in high magnetic fields","authors":"Benedikt Beckmann , Andreas Taubel , Tino Gottschall , Lukas Pfeuffer , David Koch , Franziska Staab , Enrico Bruder , Franziska Scheibel , Konstantin P. Skokov , Oliver Gutfleisch","doi":"10.1016/j.actamat.2024.120460","DOIUrl":"10.1016/j.actamat.2024.120460","url":null,"abstract":"<div><div>Ni-Co-Mn-Ti all-<em>d</em> Heusler alloys are attracting considerable attention for solid-state caloric cooling applications due to their promising combination of excellent caloric and mechanical properties. Here, we report on the maximum attainable magnetocaloric effect in Ni<sub>37</sub>Co<sub>13</sub>Mn<sub>34.5</sub>Ti<sub>15.5</sub>, which shows a first-order magnetostructural martensitic transformation around room temperature. Heat capacity measurements reveal a giant transition entropy change of 43.5<!--> <!-->J(kgK)<sup>protect relax special {t4ht=−}1</sup> and are utilized to estimate the magnetocaloric effect as well as the magnetic fields required to saturate it in isothermal and adiabatic conditions. Confirming the results based on this approach, we achieve maximum isothermal entropy changes and directly measured adiabatic temperature changes of 37.8<!--> <!-->J(kgK)<sup>protect relax special {t4ht=−}1</sup> and <span><math><mo>−</mo></math></span>20.2<!--> <!-->K, respectively. Thus, the herein reported maximum attainable magnetocaloric effect outperforms classical Ni-Mn-based Heusler alloys, such as Ni(-Co)-Mn-In. Especially the saturated adiabatic temperature change surpasses all previously published values of magnetic field-induced first-order phase transitions measured around room temperature in pulsed magnetic fields in recent years. Thereby, we demonstrate that Ni(-Co)-Mn-Ti Heusler alloys are particularly suitable for the application of sufficiently large external stimuli to fully induce the phase transition and exploit their intrinsically large caloric effect.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"282 ","pages":"Article 120460"},"PeriodicalIF":8.3,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142439293","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 : 2024-10-15DOI: 10.1016/j.actamat.2024.120465
A. Lassnig , J. Todt , M. Tkadletz , S. Zak , C. Mitterer , A.A. Medjahed , M. Burghammer , J. Keckes , M.J. Cordill , M. Meindlhumer
Residual stresses in thin film structures significantly impact their mechanical properties and affect interface delamination. Highly compressively stressed thin films buckling is the predominant interfacial failure mode due to strain energy release. In the present study the effect of cross-sectional stress and microstructural gradients of thin films on the buckling behavior are explored in a model material system consisting of a thin Cu film sputtered onto glass and a highly compressively stressed 500 nm thick Mo overlayer causing buckling delamination at the Cu-glass interface. Employing synchrotron cross-sectional X-ray nano-diffraction, multiaxial X-ray elastic strain and microstructure distributions were explored across the cross-section of the adhering and buckled bilayer, respectively. In the adhering state, a gradual thickness evolution of columnar microstructure and residual stress was found for Mo, while in Cu, no microstructure changes and only minimal stress variations were detected along the film thickness. After delamination, diffraction peak broadening and changes in unstrained lattice parameters in the Cu sublayer indicated structural defect annihilation and grain coarsening. These microstructural changes were further validated via cross-sectional transmission electron microscopy. The evaluated residual stress distributions across the two sublayers of the pristine and buckled bilayer were used to quantify the released strain energy per unit area due to buckling, amounting to 0.61 J/m². Further cross-validation of experimental stress results with finite element simulations strengthened the experimental findings, providing a comprehensive understanding of the stress distribution across the buckled bilayer.
薄膜结构中的残余应力会严重影响其机械性能，并影响界面分层。由于应变能的释放，高压缩应力薄膜屈曲是最主要的界面破坏模式。本研究探讨了薄膜的横截面应力和微观结构梯度对屈曲行为的影响，该模型材料系统由溅射到玻璃上的铜薄膜和在铜-玻璃界面上造成屈曲分层的高压缩应力 500 nm 厚的钼覆盖层组成。利用同步辐射横截面 X 射线纳米衍射技术，分别对粘附和屈曲双层材料横截面上的多轴 X 射线弹性应变和微观结构分布进行了研究。在粘附状态下，发现钼的柱状微观结构和残余应力在厚度上逐渐演变，而铜的微观结构没有变化，沿薄膜厚度只检测到极小的应力变化。分层后，铜亚层中衍射峰的扩大和非应变晶格参数的变化表明结构缺陷湮灭和晶粒粗化。横截面透射电子显微镜进一步验证了这些微观结构变化。原始双层和屈曲双层两个子层的残余应力分布评估结果被用来量化屈曲导致的单位面积释放应变能，达到 0.61 J/m²。实验应力结果与有限元模拟结果的进一步交叉验证加强了实验结果，为全面了解屈曲双分子层的应力分布提供了依据。
{"title":"Nanoscale stress and microstructure gradients across a buckled Mo-Cu bilayer: Cu self-annealing triggered by interface delamination","authors":"A. Lassnig , J. Todt , M. Tkadletz , S. Zak , C. Mitterer , A.A. Medjahed , M. Burghammer , J. Keckes , M.J. Cordill , M. Meindlhumer","doi":"10.1016/j.actamat.2024.120465","DOIUrl":"10.1016/j.actamat.2024.120465","url":null,"abstract":"<div><div>Residual stresses in thin film structures significantly impact their mechanical properties and affect interface delamination. Highly compressively stressed thin films buckling is the predominant interfacial failure mode due to strain energy release. In the present study the effect of cross-sectional stress and microstructural gradients of thin films on the buckling behavior are explored in a model material system consisting of a thin Cu film sputtered onto glass and a highly compressively stressed 500 nm thick Mo overlayer causing buckling delamination at the Cu-glass interface. Employing synchrotron cross-sectional X-ray nano-diffraction, multiaxial X-ray elastic strain and microstructure distributions were explored across the cross-section of the adhering and buckled bilayer, respectively. In the adhering state, a gradual thickness evolution of columnar microstructure and residual stress was found for Mo, while in Cu, no microstructure changes and only minimal stress variations were detected along the film thickness. After delamination, diffraction peak broadening and changes in unstrained lattice parameters in the Cu sublayer indicated structural defect annihilation and grain coarsening. These microstructural changes were further validated via cross-sectional transmission electron microscopy. The evaluated residual stress distributions across the two sublayers of the pristine and buckled bilayer were used to quantify the released strain energy per unit area due to buckling, amounting to 0.61 J/m². Further cross-validation of experimental stress results with finite element simulations strengthened the experimental findings, providing a comprehensive understanding of the stress distribution across the buckled bilayer.</div></div>","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"283 ","pages":"Article 120465"},"PeriodicalIF":8.3,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142436128","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号