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金属顶刊双语导读丨Acta Mater. Vol.211，1 Jun. 2021（下）

2021-08-08 来源：Goal Science

 

本期包含金属材料领域论文9篇，涵盖了马氏体、高熵合金、高温合金等，国内科研单位包括上海交通大学等（通讯作者单位）。

 

Vol. 211 目录

1. Unveiling the mechanism of yttrium-related microstructure inhibiting or promoting high-temperature oxidation based on Ni-Al-Y alloys

Y对Ni-Al-Y合金微观组织和高温氧化性能的影响

 

2. Atomic scale modeling of the coherent strain field surrounding Ni4Ti3 precipitate and its effects on thermally-induced martensitic transformation in a NiTi alloy

Ni4Ti3析出相共格应变场及其对NiTi合金热诱导马氏体相变影响的原子尺度模拟研究

 

3. In-situ synchrotron X-ray tomography investigation of damage mechanism of an extruded magnesium alloy in uniaxial low-cycle fatigue with ratchetting

受压镁合金棘轮单轴低周疲劳损伤机理的原位同步X射线断层扫描研究

 

4. Nitrogen-induced hardening of refractory high entropy alloys containing laminar ordered phases

通过N掺杂形成层片状有序相实现高熔点高熵合金的显著硬化

 

5. Cross-kinks control screw dislocation strength in equiatomic bcc refractory alloys

等原子比BCC高熔点合金中交叉扭结对螺位错强化作用的影响

 

6. Temperature-dependent mechanisms of dislocation–twin boundary interactions in Ni-based equiatomic alloys

等原子比Ni基体合金中位错-孪晶界相互作用机制随温度的变化

 

7. Designing L21-strengthened Al-Cr-Fe-Ni-Ti complex concentrated alloys for high temperature applications

L21相强化的Al-Cr-Fe-Ni-Ti多主元高温合金设计

 

8. Quantitative prediction of rapid solidification by integrated atomistic and phase-field modeling

通过耦合原子尺度模拟和相场模型实现快速凝过程的定量预测

 

9. A tale of two phase diagrams: Interplay of ordering and hydrogen uptake in Pd–Au–H

Pd-Au-H体系中有序态和氢相互作用的相图研究

 

 

ACTA

Vol. 211，1 Jun. 2021, 116879

1. Unveiling the mechanism of yttrium-related microstructure inhibiting or promoting high-temperature oxidation based on Ni-Al-Y alloys

Y对Ni-Al-Y合金微观组织和高温氧化性能的影响

 

Yun Wu, Yunting Li, Yuantao Xu, Maodong Kang✉, Jun Wang✉, Baode Sun

M. Kang：kangmd518@sjtu.edu.cn（上海交通大学）

J. Wang：junwang@sjtu.edu.cn（上海交通大学）

https://doi.org/10.1016/j.actamat.2021.116879

 

摘要

钇的添加能够提高镍基合金的高温氧化性能。然而，我们目前对于Y氧化行为的理解尚不深入，特别是与其他关键成分（如Al）的相互作用。我们对四种简单Ni-Al-Y 合金在800°/1000°℃空气中的氧化行为进行了研究。通过多尺度表征和热力学计算，我们发现四种合金的氧化层厚度随Y和Al浓度的变化而变化。在三种高Y含量的合金中，Y相关的微观组织对氧化过程具有强烈的驱动作用。初始组织中的Ni5Y化合物具有强烈的二次γ-Ni条带析出倾向，因此有利于形成含有混合氧化物颗粒的内氧化层，而初始组织中的γ-Ni则驱动外层NiO的形成。于粗化的不规则相界相比，密集的层状相界更有利于抑制内层的长大。在1000°C下，得益于晶界(GBs)和内氧化层前端混合氧化物的形成，少量添加Y的镍基合金抗内氧化性能显著提高。我们基于三元相图等温截面，进行了一些热力学计算，用于阐明氧化物的演化过程。通过对比复杂产物的形成情况可知，计算结果与实验结果基本吻合。

向上滑动阅览英文摘要

Yttrium is an attractive component for nickel base alloys to improve high-temperature oxidation resistance. However, the application suffers from microstructure related problem, due to less unconscious of Y-related oxidation behavior, especially interacting with other key components, such as aluminium. This study introduces the discovery of microstructure depended external and internal oxidation behaviors based on four simplified Ni-Al-Y alloys during isothermally exposing at 800°C/1000°C in air. Using multiscale microstructural characterizations and thermodynamic calculations, different oxidation layer thicknesses have been observed in the four alloys, especially varying with Y and Al concentrations. In the three high-Y-content alloys, Y-related microstructures are found to strongly drive the oxidation process. Original-Ni5Y compound with strong tendency to precipitate secondary γ-Ni strip is favorable to the formation of inner oxidation layer containing mixed oxide particles, whereas original-γ-Ni phase drives the formation of outer scale of NiO. Dense and well-configured lamella-like phase boundaries (PBs) are beneficial to inhibiting the development of the inner layer, compared to coarse and irregular PBs. The resistance to inner oxidation of minor-Y-addition alloy has been significantly improved at 1000°C, benefiting from the mixed oxides along grain boundaries (GBs) and front of inner oxidation layers. From the thermodynamic basis, a type of modified diagram retrieved from ternary isothermal section is utilized to exhibit the oxide evolution, which is consistent with experimental results, especially for those complicated products.

 

 

ACTA

Vol. 211，1 Jun. 2021, 116883

2. Atomic scale modeling of the coherent strain field surrounding Ni4Ti3 precipitate and its effects on thermally-induced martensitic transformation in a NiTi alloy

Ni4Ti3析出相共格应变场及其对NiTi合金热诱导马氏体相变影响的原子尺度模拟研究

 

Zhu Li, Fei Xiao✉, Hong Chen, Ruihang Hou, Xiaorong Cai, Xuejun Jin✉

F. Xiao：xfei@sjtu.du.cn

X. Jin：jin@sjtu.edu.cn（上海交通大学）

https://doi.org/10.1016/j.actamat.2021.116883

 

摘要

NiTi合金中的Ni4Ti3析出对于材料性能有重要影响，但析出的共格应变场及其对马氏体相变的影响，特别是对B19’变体和形貌的影响，目前尚不清楚。本研究中，我们通过分子动力学模拟，结合Eshelby方法和微弹性相场理论理论，对具有不同长宽比的Ni4Ti3析出所引起的应变场进行了研究。通过方程描述了基体中的最大应变（沿析出的中轴）及其相对位置。并对材料的马氏体形变起始温度Ms和奥氏体相变终止温度Af进行了分析预测。此外，我们还详细地对之前已发表过的三角形和人字形两种B19’自适应结构进行了详细研究。我们首次观察到了三角形和人字形的中间状态，我们把它称为混合自适应态。这种结构十分不稳定，我们对其形成过程进行了分析讨论。综上所述，本研究首次解释了析出相对于不同孪晶B19’形貌的选择作用及其对热诱导马氏体相变的原子尺度影响。

向上滑动阅览英文摘要

Precipitation of Ni4Ti3 in NiTi alloy profoundly affects material properties, while the coherency strain fields and their effects on the thermally-induced martensitic transformation are not known in detail, especially for the B19’ variants and morphologies. Therefore, molecular dynamics simulations, as well as an Eshelby solution and phase-field microelasticity theory were applied to investigate the strain fields caused by the Ni4Ti3 precipitates with different aspect ratios. The maximum strain (along the central axis of the precipitate) in the matrix and its relative position are formulated as function relationships. Ms (martensitic transformation start temperature) and Af (austenitic transformation finish temperature) during martensitic transformation were determined and analyzed. Two previously published self-accommodation B19’ structures, the triangular and “herring-bone’’ morphologies are investigated in detail. An intermediate state between the triangular and “herring-bone’’ morphologies, termed mixed self-accommodation, is observed for the first time and proved to be the most unstable structure, providing a potential design route for low hysteresis microactuators. The formation processes of these self-accommodation morphologies are analyzed and discussed. Our simulations are the first time to reveal a variety of twinned B19’ morphologies selected by precipitates and their effects on thermally-induced martensitic transformation at the atomic scale.

 

 

ACTA

Vol. 211，1 Jun. 2021, 116881

3. In-situ synchrotron X-ray tomography investigation of damage mechanism of an extruded magnesium alloy in uniaxial low-cycle fatigue with ratchetting

受压镁合金棘轮单轴低周疲劳损伤机理的原位同步X射线断层扫描研究

 

Ziyi Wang, Shengchuan Wu, Guozheng Kang✉, Hang Li, Zhengkai Wu, Yanan Fu, Philip J. Withers

G. Kang：guozhengkang@swjtu.edu.cn, guozhengkang@126.com（西南交通大学）

https://doi.org/10.1016/j.actamat.2021.116881

 

摘要

我们研究了受压AZ31Mg合金在单轴低周棘轮疲劳下的变形过程与损伤机制。我们采用不同的平均应力和应力振幅分别研究了由孪晶控制 (TDD)、滑移控制(SD)和孪晶、滑移混合控制(TDSD)下的循环变形。通过同步辐射断层扫描和扫描电子显微镜对材料中的损伤进行观测；通过电子背散射衍射和透射电子显微镜对不同载荷条件下的塑性变形机制进行表征。我们在TDD和TDSD样品中观测到大量孪晶，而在TDSD和SD样品中观测到了高密度位错和其他复杂结构。三种样品按照损伤起始位点数量由多到少排列依次为TDSD样品、TDD样品和SD样品。因为TDSD样品中存在大量孪晶引起的穿晶损伤以及<c+a>位错和孪晶共同引起的晶间损伤使；TDD样品中位错密度较低；SD样品不含孪晶。我们仅在TDSD样品中观察到了独立裂纹之间的连接。以上研究为受压镁合金的损伤演化模型提供了丰富的实验证据。

向上滑动阅览英文摘要

 

This paper elucidates the relationship between the primary deformation processes and associated damage mechanisms operating in an extruded AZ31 Mg alloy under uniaxial low-cycle fatigue with an occurrence of ratchetting. Different mean stresses and stress amplitudes were prescribed to study twinning/detwinning-dominated (TDD), twinning/detwinning and slip-dominated (TDSD), and slip-dominated (SD) cyclic deformations, respectively. In each case, the damage was examined by synchrotron radiation micro-computed tomography and scanning electron microscopy. The plastic deformation mechanism for each load case was then characterized by electron backscatter diffraction and transmission electron microscopy. Profuse twins were detected in the TDD and TDSD samples, while more complex structures and higher dislocation densities were found in the TDSD and SD samples where dislocation slip was plentiful. The TDSD sample had the most damage initiation sites owing to the transgranular damage caused by twins and the intergranular damage induced by the combined effect of <c+a> dislocations and twins, followed by the TDD sample because of the low dislocation density, while the SD sample had the fewest due to the lack of twins. Shear linkage between the isolated cracks was observed only in the TDSD sample. This provides rich evidence for the modelling of damage evolution of extruded Mg alloys.

 

 

ACTA

Vol. 211，1 Jun. 2021, 116884

4. Nitrogen-induced hardening of refractory high entropy alloys containing laminar ordered phases

通过N掺杂形成层片状有序相实现高熔点高熵合金的显著硬化

 

Joshua A. Smeltzer, B. Chad Hornbuckle, Anit K. Giri, Kristopher A. Darling, Martin P. Harmer, Helen M. Chan, Christopher J. Marvel✉

C.J. Marvel：cjm312@lehigh.edu

https://doi.org/10.1016/j.actamat.2021.116884

 

摘要

调控成分和组织是提高高熵合金(HEAs)性能的主要方法。本研究中，我们发现可以通过非金属元素掺杂形成共格有序析出，大幅提高高熵合金的硬度。我们以液氮为制冷剂，通过低温机械合金化成功制备了N掺杂的MoNbTaW高熵合金。我们在材料中观测到了富N的二次相，因此掺杂是成功的。特别地，我们通过像差校正扫描透射电镜(STEM)发现了一种独特的有序层片相，经鉴定，为四方(Mo、W)(Nb、Ta)N氮化物。此外，我们还发现了另一种复杂的碳氮化物(Nb,Ta)2CN。我们将材料在1200°C下进行了100小时的时效处理以研究陶瓷相的长大。我们利用液Ar作为冷却剂，通过高能球磨方法制备了第二种MoNbTaW合金。对这两种合金组织和性能的比较表明，复杂氮化物的形成使得MoNbTaW的硬度大幅提高，可至3-4GPa。

向上滑动阅览英文摘要

Most attempts to improve the properties of high entropy alloys (HEAs) involve the exploration of non-equimolar compositions, addition of alloying elements, and/or manipulation of the microstructure. Alternatively, this work reports on intentionally doping HEAs with non-metallic species to precipitate coherent, ordered phases in order to maximize hardness. A refractory MoNbTaW HEA was synthesized via cryogenic mechanical alloying and doped with nitrogen by using liquid nitrogen as the cryogen. Overall, the doping strategy was successful as multiple nitrogen-rich secondary phases were observed. In particular, a unique ordered laminar phase was developed and identified as tetragonal (Mo,W)(Nb,Ta)N nitride via aberration-corrected scanning transmission electron microscopy (STEM). Another complex (Nb,Ta)2CN carbonitride was also identified. The growth behaviors of the ceramic phases were studied using long term aging treatments of up to 100 hours at 1200°C. A second MoNbTaW alloy was also prepared via high-energy ball milling, without nitrogen, by using liquid Ar as the cryogen. A comparison of the two alloys’ microstructures and properties confirm that intentional formation of complex nitride phases greatly enhanced the hardness of mechanically alloyed MoNbTaW by up to 3-4 GPa.

 

 

ACTA

Vol. 211，1 Jun. 2021, 116875

5. Cross-kinks control screw dislocation strength in equiatomic bcc refractory alloys

等原子比BCC高熔点合金中交叉扭结对螺位错强化作用的影响

 

Xinran Zhou✉, Sicong He, Jaime Marian✉

X. Zhou：Xinranz1216104@g.ucla.edu

J. Marianjmarian@ucla.edu

https://doi.org/10.1016/j.actamat.2021.116875

 

摘要

具有BCC结构的高熔点多主元合金（RMEA）由于具有优异的高温应用前景，而在过去十年中受到广泛研究。这些合金大都在高温下表现出极高的强度，无法用基于热激活螺位错运动的BCC塑性标准模型解释。有研究指出，化学能量起伏是影响RMEA强度重要因素，而没有在标准模型中被考虑。本研究中，我们使用蒙特卡洛动力学模型量化了螺位错对等原子比Nb-Ta-V合金强度的贡献。我们发现沿位错线的化学能量波动会在较宽的温度范围内导致较高的平衡扭结含量，这与分子动力学模拟结果一致。其中的部分形成了交叉扭结结构，它们对螺位错运动和材料强度有重要影响。我们的模拟证实了(i)交叉扭结和自钉扎是低温下形成所谓“鸡尾酒”效应的主要原因；(ii)仅螺位错塑性不能有效解释BCC RMEA的高温强度。

向上滑动阅览英文摘要

 

Refractory multi-element alloys (RMEA) with body-centered cubic (bcc) structure have been the object of much research over the last decade due to their high potential as candidate materials for high-temperature applications. Most of these alloys display a remarkable strength at high temperatures, which cannot be explained by the standard model of bcc plasticity based on thermally-activated screw dislocation motion. Several works have pointed to chemical energy fluctuations as an essential aspect of RMEA strength that is not captured by standard models. In this work, we quantify the contribution of screw dislocations to the strength of equiatomic Nb-Ta-V alloys using a kinetic Monte Carlo model fitted to solution energetics obtained from atomistic calculations. In agreement with molecular dynamics simulations, we find that chemical energy fluctuations along the dislocation line lead to measurable concentrations of kinks in equilibrium in a wide temperature range. A fraction of these form cross-kink configurations, which are ultimately found to control screw dislocation motion and material strength. Our simulations (i) confirm that the evolution of cross kinks and self-pinning are strong contributors to the so-called ‘cocktail’ effect in this alloy at low temperature, and (ii) substantiate the notion that screw dislocation plasticity alone cannot explain the high temperature strength of bcc RMEA.

 

 

ACTA

Vol. 211，1 Jun. 2021, 116886

6. Temperature-dependent mechanisms of dislocation–twin boundary interactions in Ni-based equiatomic alloys

等原子比Ni基体合金中位错-孪晶界相互作用机制随温度的变化

 

Sho Hayakawa, Haixuan Xu✉

H. Xu：xhx@utk.edu

https://doi.org/10.1016/j.actamat.2021.116886

 

摘要

FeNiCoCrMn高熵合金具有优异的强韧性组合，且随温度降低，材料延展性显著增加。这一现象的潜在机制对于理解材料机械性能至关重要。我们通过原子尺度模拟研究了等原子比镍基合金中螺位错与共格孪晶界之间的相互作用。我们发现，这种相互作用的主要机制会随温度而变化，这可能是合金在低温下延展性增强的原因之一。进一步研究表明，与层错能和Shockley分位错间离有关的一个临界参数对这种相互作用随温度的变化有重要影响。以上研究有助于我们深入理解等原子比镍基合金的塑性变形机理，对高强塑性材料设计具有重要意义。

向上滑动阅览英文摘要

The high entropy alloy FeNiCoCrMn and its subsets have exhibited an unusual combination of strength and ductility dependance on temperature, showing a significant increase in ductility as temperature decreases. This phenomenon is intriguing, and the underlying mechanism is critical for understanding the mechanical properties of these materials. Here, we investigate the interaction between a screw dislocation and a coherent twin boundary in Ni-based equiatomic alloys using atomistic simulations. We find that the dominant mechanism for this interaction changes as a function of temperature, which could be one of the underlying causes of the enhanced ductility at cryogenic temperatures in these alloys. Further investigations reveal the interaction's temperature dependence arises from a critical parameter related to the stacking fault energy and the distance between the Shockley partial dislocations. The insights extracted herein contribute to a fundamental understanding of plastic deformation in Ni-based equiatomic alloys and can be utilized for developing design strategies to achieve superior strength and ductility in structural materials.

 

 

ACTA

Vol. 211，1 Jun. 2021, 116890

7. Designing L21-strengthened Al-Cr-Fe-Ni-Ti complex concentrated alloys for high temperature applications

L21相强化的Al-Cr-Fe-Ni-Ti多主元高温合金设计

 

Woo Chul Kim, Min Young Na, Heoun Jun Kwon, Young Sang Na, Jong Woo Won, Hye Jung Chang✉, Ka Ram Lim✉

H.J. Chang：almacore@kist.re.kr

K.R. Lim：krlim@kims.re.kr

https://doi.org/10.1016/j.actamat.2021.116890

 

摘要

对于具有纳米析出的合金而言，析出与基体之间的共格性对材料的高温机械性能至关重要。在这项工作中，我们对AlxCr13.3Fe71.5-xNi11.2Ti4 (x=8, 10, 12, 14, 16 at%) 多主元合金中BCC基体与L21析出的共格性进行了系统研究，包括析出的结构、晶格错配和由此产生的共格应变演化。当Al含量从8 at%增加到16 at%时，析出的尺寸和晶格错配减小，界面从半共格逐渐变为完全共格，从而使得基体与析出之间的弹性相互作用增加。同时析出的晶体结构从立方变为四方。随着Al含量的增加，由于固溶强化和析出强化的作用，材料室温强度连续增加。析出的强化机制也由Orowan强化变为共格强化。有趣的是，拉伸试验表明700°C下铝增加引起的强化效应进一步增强。更高程度的共格和结构畸变引起了更显著的有效应变转移和析出强化。因此，Al16Cr13.3Fe55.5Ni11.2Ti4具有更加优异的屈服强度（400.8MPa）和抗拉强度（572.9MPa）。这一强度远高于此前报导的纳米析出强化合金，表明这种合金具有优异的高温应用前景。

向上滑动阅览英文摘要

For alloys with nanoprecipitate/matrix microstructures, the lattice coherency between the two phases plays an important role in determining the mechanical performances at high temperature. In this work, we systematically investigate the AlxCr13.3Fe71.5-xNi11.2Ti4 (x=8, 10, 12, 14, 16 at%) complex concentrated alloys with an aim to enhance the lattice coherency between the BCC matrix and L21 precipitate. The precipitate microstructures, lattice misfit and the resultant coherency strain evolution are comprehensively studied. With increasing Al from 8 at% to 16 at%, the interfacial structure gradually transforms from semicoherent to fully coherent interface by the decrease in precipitate size and lattice misfit, which leads to the stronger elastic interaction between the matrix and precipitate. Meanwhile, the crystal structure of precipitate is slightly distorted from cubic to tetragonal. The yield strength of alloys at room temperature continuously increases with the addition of Al by the solid-solution strengthening and precipitation hardening effect. Here, the mechanism of precipitation hardening changes from Orowan process to coherency strengthening. Interestingly, the strengthening effect by Al addition is further amplified in the tensile test at 700 °C. The higher degree of lattice coherency and the distorted structure of the precipitate resulting from the Al addition lead to the effective strain transfer and the stronger precipitate, respectively. Therefore, the Al16Cr13.3Fe55.5Ni11.2Ti4 alloy exhibits an excellent combination of yield strength (400.8 MPa) and ultimate tensile strength (572.9 MPa). These values are much higher than those of the previously reported nanoprecipiate-strengthened alloys, suggesting that the alloy is highly promising as high temperature structural applications.

 

 

ACTA

Vol. 211，1 Jun. 2021, 116885

8. Quantitative prediction of rapid solidification by integrated atomistic and phase-field modeling

通过耦合原子尺度模拟和相场模型实现快速凝过程的定量预测

 

Sepideh Kavousi, Brian R. Novak, Dorel Moldovan, Mohsen Asle Zaeem

M. Asle Zaeem：zaeem@mines.edu✉

https://doi.org/10.1016/j.actamat.2021.116885

 

摘要

我们通过耦合原子尺度模拟和相场建模，对增材制造合金凝固过程中的胞结构生长和溶质元素捕获进行了定量预测。我们通过分子动力学模拟代替复杂实验，得到了各向异性晶体-熔体界面的自由能、动力学参数和扩散界面速度，并将其作为相场中的参数。我们在Ti-3.4at.%Ni合金中测试了耦合模型模拟快速凝固的准确性。结果表明，相场模型预测的溶质捕获与凝固界面的连续生长模型结果大体相当。预测得到的一次枝晶臂间距对扩散界面宽度不敏感，因此模型可以使用于更大尺度的体系。二维和三维相场模型模拟得到的浓度分布与配分系数分别与可与Kurz-Fisher模型和连续生长模型结果相当。与其他快速凝固计算模型相比，本模型的优势在于可以完全基于计算进行预测，而不需要进行任何实验拟合。

向上滑动阅览英文摘要

Systematic integration of atomistic simulations with phase-field modeling is presented for quantitative predictions of cellular growth and solute trapping during solidification of alloys for solidification velocities relevant to additive manufacturing. For parametrization of the phase-field model, molecular dynamics simulations are utilized as an alternative to complex experiments to obtain the anisotropic crystal-melt interface free energy, kinetic coefficient, and diffusive interface velocity. The accuracy of this integrated model is tested for rapid solidification of Ti-3.4at.%Ni alloy. The predicted solute trapping of the proposed phase-field model is comparable with the continuous growth model for solidification velocities of additive manufacturing. The predicted primary dendritic arm spacing is weakly dependent on the diffuse interface width enabling simulations in larger length scales. The concentration profile and partition coefficient obtained from both two-and three-dimensional phase-field simulations are comparable to the results of Kurz-Fisher's analytical and continuous growth models, respectively. Unlike other computational models for rapid solidification, the proposed model enables predictions completely based on computations without fitting to experiments.

 

 

ACTA

Vol. 211，1 Jun. 2021, 116893

9. A tale of two phase diagrams: Interplay of ordering and hydrogen uptake in Pd–Au–H

Pd-Au-H体系中有序态和氢相互作用的相图研究

 

J. Magnus Rahm, Joakim Löfgren, Erik Fransson, Paul Erhart✉

P. Erhart：erhart@chalmers.se

https://doi.org/10.1016/j.actamat.2021.116893

 

摘要

Pd-Au纳米合金能够无延迟地可逆吸收/释放氢，因此是一种优秀的氢传感材料。对于传感材料而言，吸放氢等温线的可重复性和稳定性十分重要。研究表明，短程和长程化学有序对等温线有一定影响，但相关研究并不深入。本研究中，我们使用合金团簇的膨胀来描述在较宽浓度范围内Pd-Au合金的吸放氢热力学。我们通过调控退火温度和氢分压得到了样品的不同有序状态，并研究了这些不同化学有序态是如何影响合金的吸放氢等温线，进而影响材料性能的。研究表明，当H2分压足够高时，材料中将形成长程有序的L12相。我们绘制了250K到500K的相图，当体系中存在氢气时，体系在完全平衡态下将发生相分离，这与准平衡条件下截然不同。我们研究成功解释了Pd-Au合金吸放氢等温线随时间推移保持稳定的实验现象，并揭示了这一特性失效的可能情况。

向上滑动阅览英文摘要

Due to their ability to reversibly absorb/desorb hydrogen without hysteresis, Pd–Au nanoalloys have been proposed as materials for hydrogen sensing. For sensing, it is important that absorption/desorption isotherms are reproducible and stable over time. A few studies have pointed to the influence of short and long range chemical order on these isotherms, but many aspects of the impact of chemical order have remained unexplored. Here, we use alloy cluster expansions to describe the thermodynamics of hydrogen in Pd–Au in a wide concentration range. We investigate how different chemical orderings, corresponding to annealing at different temperatures as well as different external pressures of hydrogen, impact the behavior of the material with focus on its hydrogen absorption/desorption isotherms. In particular, we find that a long-range ordered L12 phase is expected to form if the H2 pressure is sufficiently high. Furthermore, we construct the phase diagram at temperatures from 250 K to 500 K, showing that if full equilibrium is reached in the presence of hydrogen, phase separation can often be expected to occur, in stark contrast to the phase diagram in para-equilibrium. Our results explain the experimental observation that absorption/desorption isotherms in Pd–Au are often stable over time, but also reveal pitfalls for when this may not be the case.