登陆 menu
当前位置：首页 > 实用信息

金属顶刊双语导读丨Acta Mater. Vol.217，15 Sep. 2021

2021-12-18 来源：GS-Metals

 

本期包含金属材料领域论文17篇，涵盖了高温合金、钛合金、形状记忆合金等，国内科研单位包括中科院沈阳金属所、上海交通大学、北京科技大学、清华大学等（通讯作者单位）。

 

Vol. 217 目录

1. Influence of microstructure on the application of Ni-Mn-In Heusler compounds for multicaloric cooling using magnetic field and uniaxial stress

微观组织对Ni-Mn-In Heusler复合材料磁场和单轴应力多热冷却应用的影响

 

2. Understanding imprint formation, plastic instabilities and hardness evolutions in FCC, BCC and HCP metal surfaces

了解FCC, BCC和HCP金属表面的压痕形成，塑性不稳定性和硬度变化

 

3. A unified description of mechanical and actuation fatigue crack growth in shape memory alloys

形状记忆合金中机械和驱动疲劳裂纹扩展的统一描述

 

4. Dynamics of Ga penetration in textured Al polycrystal revealed through multimodal three-dimensional analysis

通过多模态三维分析揭示了Ga在织构多晶铝中的渗透动力学

 

5. Removing basal-dissociated <c+a> dislocations by {10-12} deformation twinning in magnesium alloys

通过{10-12}变形孪晶去除镁合金中的基面离解的<c+a>位错

 

6. Bubble formation in helium-implanted nanostructured ferritic alloys at elevated temperatures

在高温下植入氦气的纳米结构铁素体合金中的气泡形成

 

7. Energy landscape modeling of crystal nucleation

晶体成核的能量景观建模

 

8. Theoretical investigation of the 70.5° mixed dislocations in body-centered cubic transition metals

体心立方过渡金属中70.5°混合位错的理论研究

 

9. An expansion of the Fisher model for concentration dependent grain boundary diffusion

浓度依赖晶界扩散的Fisher模型的扩展

 

10. Thermodynamic properties of the Yb-Sb system predicted from first-principles calculations

用第一性原理计算预测了Yb-Sb体系的热力学性质

 

11. Deformation mechanisms of Mg-Ca-Zn alloys studied by means of micropillar compression tests

采用微柱压缩试验研究Mg-Ca-Zn合金的变形机理

 

12. Stress-sensitive fatigue crack initiation mechanisms of coated titanium alloy

涂层钛合金应力敏感疲劳裂纹萌生机制研究

 

13. Revealing carbide precipitation effects and their mechanisms during quenching-partitioning-tempering of a high carbon steel: Experiments and Modeling

揭示高碳钢淬火-配分-回火过程中碳化物析出效应及其机理:实验与模拟

 

14. Insights into the selection mechanism of Widmanstätten growth by phase-field calculations

通过相场计算深入了解Widmanstätten生长的选择机制

 

15. Thermodynamics and design of nanocrystalline alloys using grain boundary segregation spectra

基于晶界偏析光谱的纳米晶合金热力学及设计

 

16. Multiphase field modeling of grain boundary migration mediated by emergent disconnections

由断裂介导的晶界迁移的多相场模拟

 

17. On the origin of mosaicity in directionally solidified Ni-base superalloys

定向凝固镍基高温合金镶嵌现象的起源

 

 

ACTA

Vol. 217，15 Sep. 2021, 117157

1. Influence of microstructure on the application of Ni-Mn-In Heusler compounds for multicaloric cooling using magnetic field and uniaxial stress

微观组织对Ni-Mn-In Heusler复合材料磁场和单轴应力多热冷却应用的影响

 

Lukas Pfeuffer✉, Adrià Gràcia-Condal, Tino Gottschall, David Koch, Tom Faske, Enrico Bruder, Jonas Lemke, Andreas Taubel, Semih Ener, Franziska Scheibel, Karsten Durst, Konstantin P.Skokov, Lluís Mañosa, Antoni Planes, Oliver Gutfleisch

Lukas Pfeuffer: lukas.pfeuffer@tu-darmstadt.de

https://doi.org/10.1016/j.actamat.2021.117157

 

摘要

利用镍锰基超磁性形状记忆合金对不同外部刺激（如磁场、单轴应力和静水压力）的巨大热响应的新型多热量冷却是一种有前途的节能和环保制冷的方法。然而，文献中很少讨论同时或连续施加几个外部场时微观组织的作用。本研究通过真空铸造和电弧熔炼合成了三元Ni-Mn-In合金，并分析了合金组织对磁场和单轴应力响应的影响。结合SEM-EBSD和应力-应变数据，揭示了织构对应力诱导的马氏体相变的显著影响。结果表明，<001>织构可以极大的降低临界转变应力。进一步研究了晶粒尺寸对材料失效的影响，以及它对磁场诱导相变动力学的影响。此外，本研究还建立了温度-应力和温度-磁场相图，并以ΔsT和ΔTad表征了单片热工性能。而且循环的ΔTad值与在多热量利用-磁滞循环中取得的值进行了比较。事实证明，真空铸造组织和两种刺激的结合能够在适度的外部场中实现出色的热量效应，且显著地超过了单一的热效应。特别是对于Ni-Mn-In来说，当施加55MPa的中等连续应力时，在 1.9T的磁场中的最大循环效应增加了200%以上，达到-4.1K。研究结果表明了微观组织对于Ni-Mn基超磁性形状记忆合金的多热冷却具有关键的作用。

向上滑动阅览英文摘要

Novel multicaloric cooling utilizing the giant caloric response of Ni-Mn-based metamagnetic shape-memory alloys to different external stimuli such as magnetic field, uniaxial stress and hydrostatic pressure is a promising candidate for energy-efficient and environmentally-friendly refrigeration. However, the role of microstructure when several external fields are applied simultaneously or sequentially has been scarcely discussed in literature. Here, we synthesized ternary Ni-Mn-In alloys by suction casting and arc melting and analyzed the microstructural influence on the response to magnetic fields and uniaxial stress. By combining SEM-EBSD and stress-strain data, a significant effect of texture on the stress-induced martensitic transformation is revealed. It is shown that a <001> texture can strongly reduce the critical transformation stresses. The effect of grain size on the material failure is demonstrated and its influence on the magnetic-field-induced transformation dynamics is investigated. Temperature-stress and temperature-magnetic field phase diagrams are established and single caloric performances are characterized in terms of ΔsT and ΔTad. The cyclic ΔTad values are compared to the ones achieved in the multicaloric exploiting-hysteresis cycle. It turns out that a suction-cast microstructure and the combination of both stimuli enables outstanding caloric effects in moderate external fields which can significantly exceed the single caloric performances. In particular for Ni-Mn-In, the maximum cyclic effect in magnetic fields of 1.9 T is increased by more than 200 % to -4.1 K when a moderate sequential stress of 55 MPa is applied. Our results illustrate the crucial role of microstructure for multicaloric cooling using Ni-Mn-based metamagnetic shape-memory alloys.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117122

2. Understanding imprint formation, plastic instabilities and hardness evolutions in FCC, BCC and HCP metal surfaces

了解FCC, BCC和HCP金属表面的压痕形成，塑性不稳定性和硬度变化

 

Javier Varillas, Jan Očenášek, Jordi Torner, Jorge Alcalá

https://doi.org/10.1016/j.actamat.2021.117122

 

摘要

金属表面的纳米压痕实验的特点是随着永久纳米压痕和致密缺陷网络的发展，纳米压痕实验开始出现塑性不稳定性。本论文使用实际尺寸的钝化（球形）尖端对FCC、BCC和HCP金属的纳米压痕实验进行大量的分子动力学模拟，并将结果与实验测量进行详细比较。研究结果表明了缺陷过程决定了接触塑性变形阻力，具有突然塑性不稳定性的过渡阶段的发展以及以恒定位错密度（ρp）处硬度（pp）趋于平稳为特征的自相似稳态的演变过程。永久纳米压痕的发生受堆垛层错和纳米孪晶、整个压痕过程中纳米结构区域和微晶的堆积、表面螺旋位错的交叉滑移和交叉扭结以及塑性区内缺陷再活动事件的发生所制约。由于这些机制，硬度 （pp）和杨氏模量（E）之间的比值在BCC的Ta 和Fe中变得更高，其次是FCC 的Al、HCP的Mg 和大层错宽度的FCC的Ni和Cu。最后，当纳米压痕的形成与缩进的微小材料体积的单轴响应相关时，硬度与屈服强度之比（pp /σys）从7 变化到10，这在很大程度上超过了连续塑性的界限（2.8）。本研究的结果对理解压痕尺寸效应具有普遍意义，其中极端纳米级硬度值的出现与大应变梯度下独特的压痕形成过程的发生有关。

向上滑动阅览英文摘要

Nanoindentation experiments in metal surfaces are characterized by the onset of plastic instabilities along with the development of permanent nanoimprints and dense defect networks. This investigation concerns massive molecular dynamics simulations of nanoindentation experiments in FCC, BCC and HCP metals using blunted (spherical) tips of realistic size, and the detailed comparison of the results with experimental measurements. Our findings shed light on the defect processes which dictate the contact resistance to plastic deformation, the development of a transitional stage with abrupt plastic instabilities, and the evolution towards a self-similar steady-state characterized by the plateauing hardness pp at constant dislocation density ρp. The onset of permanent nanoimprints is governed by stacking fault and nanotwin interlocking, the buildup of nanostructured regions and crystallites throughout the imprint, the cross-slip and cross-kinking of surfaced screw dislocations, and the occurrence of defect remobilization events within the plastic zone. As a result of these mechanisms, the ratio between the hardness pp and the Young's modulus E becomes higher in BCC Ta and Fe, followed by FCC Al, HCP Mg and large stacking fault width FCC Ni and Cu. Finally, when nanoimprint formation is correlated with the uniaxial response of the indented minuscule material volume, the hardness to yield strength ratio, pp/σys, varies from ≈7 to ≈10, which largely exceeds the continuum plasticity bound of ≈2.8. Our results have general implications to the understanding of indentation size-effects, where the onset of extreme nanoscale hardness values is associated with the occurrence of unique imprint-forming processes under large strain gradients.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117155

3. A unified description of mechanical and actuation fatigue crack growth in shape memory alloys

形状记忆合金中机械和驱动疲劳裂纹扩展的统一描述

 

Behrouz Haghgouyan, Benjamin Young, Sezer Picak, Theocharis Baxevanis✉, Ibrahim Karaman, Dimitris C.Lagoudas

Theocharis Baxevanis: tbaxevanis@uh.edu; tbaxevanis@gmail.com

https://doi.org/10.1016/j.actamat.2021.117155

 

摘要

疲劳损伤容限方法依靠断裂力学概念来明确说明疲劳裂纹的扩展过程。这些方法通常采用Paris方程，该方程通过实验校准的参数，将每周期的裂纹增长与循环加载期间的应力强度系数ΔK的变化范围联系起来。对近裂纹尖端应力和应变场的单一参数描述的有效性条件限制了ΔK对形状记忆合金（SMA）在一般热机械加载路径下的抗疲劳裂纹增长的适用性。这些条件对于循环ΔJ积分方法来说是非常宽松的，它可以在更广泛的加载条件和几何配置中实现相似。因此，ΔJ可以作为SMAs中抗热机械疲劳裂纹扩展的潜在统一描述符，这一论断在本论文中对来自高温SMA Ni50.3Ti29.7Hf20的纯机械和驱动疲劳裂纹扩展实验的数据进行了验证。在后者中，紧凑的拉伸试样在恒定的负载下，在允许稳定相在每个循环中交替的上限和下限循环温度之间进行热循环。结果表明，基于ΔJ积分的Paris型幂律裂纹扩展表达式可以用一组单一参数来拟合这两类实验的疲劳裂纹增长速率数据。这种针对驱动和机械疲劳裂纹扩展速率的新分析方法为SMAs中的疲劳裂纹扩展提供了一个统一的描述，并且可以从更容易检测的机械疲劳裂纹扩展速率来估计出测量起来很费力且具有挑战性驱动疲劳裂纹扩展速率。

向上滑动阅览英文摘要

The damage tolerance approaches to fatigue rely on fracture mechanics concepts to explicitly account for the fatigue crack growth process. These approaches typically adopt the Paris equation, which relates the crack growth per cycle to the range of variation of the stress intensity factor, ΔK, during cyclic loading by means of experimentally calibrated parameters. Conditions on the validity of a single parameter description of the near crack tip stress and strain fields restrict the applicability of ΔK to fatigue crack growth resistance in Shape Memory Alloys (SMAs) under general thermomechanical loading paths. These conditions are substantially relaxed for the cyclic ΔJ–integral approach, which can achieve similitude over a wider range of loading conditions and geometric configurations. Thus, ΔJ qualifies as a potential unified descriptor of thermomechanical fatigue crack growth resistance in SMAs, an assertion, which is tested in this work for data from both purely mechanical and actuation fatigue crack growth experiments of a high temperature SMA, Ni50.3Ti29.7Hf20. In the latter, compact tension specimens are subjected to thermal cycling under constant load between an upper and a lower cycle temperature that allows for the stable phase to alternate in each cycle. It is shown here that a Paris-type power-law crack growth expression based on the ΔJ-integral can fit fatigue crack growth rate data from both types of experiments with a single set of parameters. This new analysis method for both actuation and mechanical fatigue crack growth rates provides a unified description for fatigue crack growth in SMAs and can allow estimating actuation fatigue crack growth rates, laborious and challenging to measure, from easier to detect mechanical fatigue crack growth rates.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117145

4. Dynamics of Ga penetration in textured Al polycrystal revealed through multimodal three-dimensional analysis

通过多模态三维分析揭示了Ga在织构多晶铝中的渗透动力学

 

N. Lu, S. Moniri, M.R. Wiltse, J. Spielman, N. Senabulya, A.J. Shahani✉

A.J.Shahani: shahani@umich.edu

https://doi.org/10.1016/j.actamat.2021.117145

 

摘要

本研究对液态 Ga 在温度为31.9°C的多晶体Al棒中的渗透进行了原位研究。基于实验室的新型多模态X射线成像平台的帮助下，使我们能够描述三维（3D）晶粒结构、Ga的润湿行为以及两者之间的关联性。与随机分布相比，样品沿着[001]方向显示出强烈的织构以及更高比例的低角度晶界（LAGBs），这表明高角度晶界（HAGBs）的连通性较差。在接触液态金属1小时后检测到沿HAGBs的Ga通道，但这种通道在长时间退火后逐渐消失。本研究进一步从几何渗透理论和扩散理论的角度来解释这一现象，这些理论指出了有限HAGB连通性和增强的通过位错管从HAGB渗漏到体外的Ga扩散的协同效应。本研究提供了关于织构和晶界连通性对液态金属脆化动力学的影响的详细见解，与具有高层错能的抗脆性材料的晶界工程有关。

向上滑动阅览英文摘要

We investigate in situ the penetration of liquid Ga in a polycrystalline Al rod at a temperature of 31.9°C. Our study is made possible with the aid of a novel, multimodal laboratory-based X-ray imaging platform, which enables us to characterize the three-dimensional (3D) grain structure, Ga wetting behavior, and correlations of the two. Our sample shows a strong texture along [001] and a higher fraction of low-angle grain boundaries (LAGBs) compared to a random distribution, signifying a poor connectivity of high-angle grain boundaries (HAGBs). We detect channels of Ga along HAGBs after 1-hour of exposure to the liquid metal, but such channels gradually disappear upon prolonged annealing. We interpret this phenomenon in the lens of geometric percolation theory and diffusion theory, which point to the synergistic effects of a limited HAGB connectivity and the enhanced Ga leakage from HAGBs into the bulk through dislocation-pipe diffusion. This work provides detailed insight into the influences of texture and grain boundary connectivity on the dynamics of liquid metal embrittlement, with relevance to grain boundary engineering of embrittlement-resistant materials with high stacking fault energy.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117170

5. Removing basal-dissociated <c+a> dislocations by {10-12} deformation twinning in magnesium alloys

通过{10-12}变形孪晶去除镁合金中的基面离解的<c+a>位错

 

Xinzhe Zhou, Huhu Su, Hengqiang Ye, Zhiqing Yang✉

Zhiqing Yang: yangzq@imr.ac.cn; yangzq34@yahoo.com, 中科院沈阳金属所

https://doi.org/10.1016/j.actamat.2021.117170

 

摘要

基于原子分辨率观察、界面缺陷理论和分子动力学（MD）模拟，研究了循环变形的 Mg 合金中{10-12}孪晶界（TBs）与位错的反应。原子分辨率观察提供了{10-12}孪晶界分别与基面<a60>、基面解离的<c+a>位错以及孪晶界的四次迁移发生反应的证据。MD模拟结果表明， Mg中固定的基面解离的<c+as>, <c+a60> 和<c>位错可以被纳入{10-12}孪晶界中去产生台阶。并且在低剪应力的作用下，台阶可以与孪晶和去孪晶时的孪晶界一起移动。而且这种台阶在同时施加剪切应力和法向应力的情况下通常可以产生<a60>位错。重要的是，在{10-12} 变形孪晶中，将固定的基面解离的<c+a>位错转变为滑动的<a60>位错所需的法向应力要远低于将基面<a60>位错转变为<c+a>位错所需的法向应力。本研究的结果可能对全面了解变形孪晶、<c+a>位错以及它们在镁合金塑性变形中的相互作用/反应有重要意义。

向上滑动阅览英文摘要

Reactions of {10-12} twin boundaries (TBs) with dislocations in a Mg alloy subjected to cyclic deformation were studied and modeled, based on atomic-resolution observations, theory of interfacial defects and molecular dynamics (MD) simulations. Atomic-resolution observations provide evidence for occurrence of reactions of {10-12} TBs with basal <a60> and basal-dissociated <c+a> dislocations upon back and forth migration of {10-12} TBs, respectively, during cyclic deformation. MD simulations show that immobile basal-dissociated <c+as>, <c+a60> and <c> dislocations in Mg can be incorporated into {10-12} TBs to produce steps which can move together with the TBs upon twinning/detwinning under low shear stresses. And such steps can usually emit <a60> dislocations under simultaneous application of shear and normal stresses. Importantly, the normal stresses required to transmute immobile basal-dissociated <c+a> dislocations to glissile <a60> dislocations are much lower than those required to transmute basal <a60> dislocations to <c+a> dislocations during {10-12} deformation twinning. Our results may have implications for comprehensive understanding of the roles of deformation twinning, <c+a> dislocations, and their interactions/reactions in plastic deformation of Mg alloys.

 

 

 

ACTA

Vol. 217，15 Sep. 2021, 117165

6. Bubble formation in helium-implanted nanostructured ferritic alloys at elevated temperatures

在高温下植入氦气的纳米结构铁素体合金中的气泡形成

 

Yan-Ru Lin✉, Wei-Ying Chen, Lizhen Tan, David T.Hoelzer, Zhanfeng Yan, Cheng-Yu Hsieh, Chun-Wei Huang, Steven John Zinkle

Yan-Ru Lin: ylin52@vols.utk.edu

https://doi.org/10.1016/j.actamat.2021.117165

 

摘要

通过扫描/透射电子显微镜（S/TEM）对Fe-9/10Cr二元合金和两种弥散强化纳米结构合金（CNA3和14YWT，分别含有直径为5-10nm 的碳化物和氧化物颗粒）在500到900℃ 下原位和非原位植入约10000 appm 后的氦气后氦气气泡的形成进行了研究。高分辨率STEM 图像和电子能量损失光谱（EELS）的结合结果显示14YWT中的Y-Ti-O纳米颗粒是均匀分布的，并表现出气泡附着在纳米团簇上的一对一的关系。在900℃的原位实验中，Fe-10Cr 模型合金的晶界开裂很严重，但在纳米结构合金中没有发现。从500到900°C的范围内，气泡大小一般随着辐照温度的增加而增加，而气泡密度随着温度的增加而减少。在相同的温度下，注入材料中的气泡大小依次为Fe-9/10Cr > CNA3 > 14YWT，而气泡密度则呈现相反的顺序。观察到的纳米结构合金的气泡数密度与纳米颗粒密度相当，表明这两种合金中的纳米颗粒都能有效地捕获氦元素。研究结果表明，在纳米结构合金中可以通过将氦气封存到较小的气泡中（这导致较低的体积膨胀值）来控制非常高的氦气浓度，并将氦气从晶界中屏蔽。这可以归因于与纳米团簇相关的更高的吸收强度或不同类型的纳米团簇之间的氦捕获能力。

向上滑动阅览英文摘要

Helium bubble formation was examined by scanning/transmission electron microscopy (S/TEM) in Fe-9/10Cr binary alloys and two dispersion strengthened nanostructured alloys (CNA3 and 14YWT containing 5–10 nm diameter carbide and oxide particles, respectively) after ex-situ and in-situ He implantation to ~10,000 appm at 500 to 900 °C. The combination of high-resolution STEM images and electron energy loss spectroscopy (EELS) revealed that the Y-Ti-O nanoparticles in 14YWT were uniformly distributed and exhibited a one-to-one relationship for bubble attachment to the nanoclusters. In the in-situ experiment at 900 °C, grain boundary cracking was severe in the Fe-10Cr model alloy, but not in the nanostructured alloys. From 500 to 900 °C, the bubble size generally increased with increasing irradiation temperature, while the bubble density decreased with increasing temperature. At the same temperatures, the bubble size in the implanted materials was in the order of Fe-9/10Cr > CNA3 > 14YWT, while the bubble density showed the opposite order. The observed bubble number densities for the nanostructured alloys are comparable to the nanoparticle density, suggesting that the nanoparticles in both alloys were effective in trapping He. Our results indicate that very high He concentrations can be managed in nanostructured alloys by sequestering the helium into smaller bubbles (which leads to a lower volume swelling value) and to shield He from the grain boundaries. This can be attributed to the much higher sink strength associated with the nanoclusters or the He trapping ability between different types of nanoclusters.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117163

7. Energy landscape modeling of crystal nucleation

晶体成核的能量景观建模

 

Collin J. Wilkinson, Daniel R. Cassar, Anthony V. DeCeanne, Katelyn A. Kirchner, Matthew E. McKenzie, Edgar D. Zanotto, John C. Mauro✉

John C. Mauro: jcm426@psu.edu

https://doi.org/10.1016/j.actamat.2021.117163

 

摘要

成核是所有材料科学中一个关键的相变过程。在晶体成核方面，对成核率的准确认识对于设计下一代玻璃陶瓷和其他复合材料至关重要；然而，晶体成核率随温度的定量预测仍然难以实现。这项工作提出了一种能量景观方法来说明成核的热力学和动力学。这种能量景观方法与作为模型的二硅酸钡系统的实验成核数据显示出相当的一致性。它还被用来深入了解经典 成核理论（CNT）的基本物理学和计算成核率的新方法。

向上滑动阅览英文摘要

 

Nucleation is a crucial phase transformation process across all materials science. In the context of crystal nucleation, accurate knowledge of the nucleation rate is essential for the design of next-generation glass-ceramic and other composite materials; however, the quantitative prediction of crystal nucleation rate versus temperature remains elusive. This work proposes an energy landscape method to account for the thermodynamic and kinetics aspects of nucleation. This energy landscape approach shows fair agreement with experimental nucleation data for the barium disilicate system used as a model. It is also used to gain insight into the fundamental physics of classical nucleation theory (CNT) and a new method to compute nucleation rates.

 

 

 

ACTA

Vol. 217，15 Sep. 2021, 117154

8. Theoretical investigation of the 70.5° mixed dislocations in body-centered cubic transition metals

体心立方过渡金属中70.5°混合位错的理论研究

 

Lorenz Romaner✉, Tapaswani Pradhan, Anastasiia Kholtobina, Ralf Drautz, Matous Mrovec

Lorenz Romaner: lorenz.romaner@unileoben.ac.at

https://doi.org/10.1016/j.actamat.2021.117154

 

摘要

体心立方（bcc）金属的低温塑性受12 <111>螺旋位错的控制，因为它们的核心是紧凑的、非平面的。有人提出70.5°混合（M111）位错也可能表现出特殊的核心结构和相当大的 Peierls 应力，但理论和实验证据仍然不完整。在本研究中，在原子模拟的基础上对五种bcc过渡金属中的M111位错进行了详细的比较研究。采用密度泛函理论和半经验的原子间势来研究M111位错的核心结构和 Peierls 势垒。计算结果表明，对M111特性的可靠预测不仅对原子间势的可靠性提出了非常严格的考验，而且对第一原理计算也是一种挑战，需要进行仔细的收敛研究。研究显示，不同的bcc过渡金属的Peierls势垒和应力有很大的不同。W 和Mo有相当大的势垒，而Nb、Ta和Fe的势垒则相当小。本研究的预测结果与内摩擦测量结果一致，并提供了对bcc金属塑性的新见解。

向上滑动阅览英文摘要

The low-temperature plasticity of body-centered cubic (bcc) metals is governed by 12<111> screw dislocations due to their compact, non-planar core. It has been proposed that 70.5° mixed (M111) dislocations may also exhibit special core structures and comparably large Peierls stresses, but the theoretical and experimental evidence is still incomplete. In this work, we present a detailed comparative study of the M111 dislocation in five bcc transition metals on the basis of atomistic simulations. We employ density functional theory and semi-empirical interatomic potentials to investigate both the core structure and the Peierls barrier of the M111 dislocation. Our calculations demonstrate that reliable prediction of M111 properties presents not only a very stringent test for the reliability of interatomic potentials but is also challenging for first-principles calculations for which careful convergence studies are required. Our study reveals that the Peierls barrier and stress vary significantly for different bcc transition metals. Sizable barriers are found for W and Mo while for Nb, Ta and Fe the barrier is comparably small. Our predictions are consistent with internal friction measurements and provide new insights into the plasticity of bcc metals.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117056

9. An expansion of the Fisher model for concentration dependent grain boundary diffusion

浓度依赖晶界扩散的Fisher模型的扩展

 

M. Short, K. Woll✉

K. Woll: karsten.woll@kit.edu

https://doi.org/10.1016/j.actamat.2021.117056

 

摘要

在考虑浓度相关的晶界扩散时，在Fisher 模型的边界条件中衍生出一个额外的项，用于在低扩散剂浓度条件下快速扩散边界的原子传输，从而形成了一个扩展模型。使用隐式有限差分模型对其有效性进行了评估，该模型表明最小和最大晶界扩散值之间至少要有0.5到0.6 个数量级的差异才能观察到显著的影响。本研究也对晶界扩散系数随浓度的增加或减少的情况进行了研究。虽然对测量的晶界扩散系数的影响可以忽略不计，但晶界扩散的浓度依赖性大大影响了晶界周围的元素分布。后者直接影响纳米晶材料中晶粒长大或相变等与晶界有关的冶金现象。

向上滑动阅览英文摘要

In accounting for concentration dependent grain boundary diffusion, an extra term is derived and added to the boundary condition in Fisher’s Model for atomic transport in fast diffusing boundaries under the condition of low diffusant concentration resulting in an expanded model. The validity of this is evaluated using an implicit finite difference model which shows that a minimum of around 0.5–0.6 order of magnitude difference between the minimum and maximum grain boundary diffusion values is necessary for a significant effect to be observed. This was investigated for a grain boundary diffusion coefficient that exponentially increased and decreased with concentration. Whereas effects on measured grain boundary diffusion coefficients are evaluated to be negligible, the concentration dependency of the grain boundary diffusion substantially affects the elemental distribution in the surrounding of the grain boundary. The latter directly influences grain boundary related metallurgical phenomena such as grain growth or phase transformations in nanocrystalline materials.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117169

10. Thermodynamic properties of the Yb-Sb system predicted from first-principles calculations

用第一性原理计算预测了Yb-Sb体系的热力学性质

 

XiaoYu Chong✉, Jorge Paz Soldan Palma, Yi Wang, Shun-Li Shang, Fivos Drymiotis, Vilupanur A. Ravi, Kurt E. Star, Jean-Pierre Fleurial, Zi-Kui Liu

XiaoYu Chong: chongxiaoyu007@163.com, 昆明理工大学

https://doi.org/10.1016/j.actamat.2021.117169

 

摘要

本研究通过基于第一性原理的准谐波声子方法研究了Yb-Sb 系统的热力学特性，得到了随温度变化的等压热容、熵、生成焓、等温体模量和热膨胀。研究了使用不同的交换相关函数和赝势对热力学性质的影响。结果显示，结合Perdew-Burker-Ernzerhof 固体泛函修正法（PBEsol）和所有f电子冻结在核内的赝势是最佳选择。这种组合导致了对相对相稳定性和热力学性质的总体良好的描述，但岩盐YbSb化合物除外，该化合物在凸壳以上的能量为25 kJ/mol-atom。这种差异可能是由于岩盐YbSb结构和其他Yb-Sb化合物之间的Yb价态发生了变化。此外，目前的计算结果表明，Yb16Sb11化合物是稳定的。对拉伸力常数的分析表明，极强的Yb-Sb 键是Yb11Sb10、Yb16Sb11、h-Yb5Sb3和Yb4Sb3在高温下稳定的原因。

向上滑动阅览英文摘要

In the present work, thermodynamic properties of the Yb-Sb system have been studied by first-principles based quasiharmonic phonon approach, reporting the temperature-dependent isobaric heat capacity, entropy, formation enthalpy, isothermal bulk modulus, and thermal expansion. The effects by using different exchange-correlation functionals and the pseudopotentials on thermodynamic properties are examined. The results reveal that the combined Perdew-Burker-Ernzerhof functional revised for solids (PBEsol) together with the pseudopotential with all f-electrons frozen in the core is the best choice. This combination leads to an overall good description of the relative phase stabilities and thermodynamic properties, except for the rocksalt YbSb compound which is calculated to have an energy of ~25 kJ/mol-atom above the convex hull. The discrepancy is due probably to the change of the Yb valence states between the rocksalt YbSb structure and the other Yb-Sb compounds. Furthermore, the present calculations show that the Yb16Sb11 compound is stable. The analysis of stretching force constants demonstrates that the extremely strong Yb-Sb bonding is responsible for the stabilities of Yb11Sb10, Yb16Sb11, h-Yb5Sb3, and Yb4Sb3 at high temperatures.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117151

11. Deformation mechanisms of Mg-Ca-Zn alloys studied by means of micropillar compression tests

采用微柱压缩试验研究Mg-Ca-Zn合金的变形机理

 

Jingya Wang, Yiwen Chen, Zhe Chen, Javier Llorca✉, Xiaoqin Zeng✉

Javier Llorca: javier.llorca@imdea.org

Xiaoqin Zeng: xqzeng@sjtu.edu.cn, 上海交通大学

https://doi.org/10.1016/j.actamat.2021.117151

 

摘要

通过对不同取向的单晶微柱进行压缩试验，测量了固溶体中的Ca和Zn对镁合金中基面滑移<a>、压缩孪晶和锥形滑移<c+a>的临界分解剪切应力（CRSS）的影响。与纯Mg相比，溶质原子使基面滑移的CRSS增加到13.5MPa ，而锥形滑移的CRSS低于85MPa，塑性各向异性明显降低。此外，孪晶成核和生长的CRSS非常相似（约37 MPa），而孪晶生长的CRSS值较大，阻碍了热机械加工过程中孪晶的生长。最后，发现了棱形滑移<a>和基面和棱形位错之间的交叉滑移的证据。结果表明，合金塑性各向异性的降低，不同滑移系统和交叉滑移的激活，以及大的CRSS促进孪晶生长的弱基面织构是改善Mg-Ca-Zn合金的延展性和成形性的原因。

向上滑动阅览英文摘要

The effect of Ca and Zn in solid solution on the critical resolved shear stress (CRSS) of <a> basal slip, tensile twinning and <c+a> pyramidal slip in Mg alloys has been measured through compression tests on single crystal micropillars with different orientations. The solute atoms increased the CRSS for basal slip to ~ 13.5 MPa, while the CRSS for pyramidal slip was lower than 85 MPa, reducing significantly the plastic anisotropy in comparison with pure Mg. Moreover, the CRSSs for twin nucleation and growth were very similar (~ 37 MPa) and the large value of the CRSS for twin growth hindered the growth of twins during thermo-mechanical processing. Finally, evidence of <a> prismatic slip and cross-slip between basal and prismatic dislocations was found. It is concluded that the reduction of plastic anisotropy, the activation of different slip systems and cross-slip and the weak basal texture promoted by the large CRSS for twin growth are responsible for the improved ductility and formability of Mg-Ca-Zn alloys.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117179

12. Stress-sensitive fatigue crack initiation mechanisms of coated titanium alloy

涂层钛合金应力敏感疲劳裂纹萌生机制研究

 

Yanyun Bai, Tao Guo, Jiawei Wang, Jin Gao, Kewei Gao, Xiaolu Pang✉

Xiaolu Pang: pangxl@mater.ustb.edu.cn, 北京科技大学

https://doi.org/10.1016/j.actamat.2021.117179

 

摘要

硬质涂层的存在会使金属基体的疲劳寿命降低到一个极低的水平，导致承重结构的灾难性失效。遗憾的是，目前的疲劳裂纹萌生机制很难解释现有的一些实验现象，预防指导理论也仍然缺乏。本研究通过对TiN涂层的Ti-6Al-4V合金进行拉伸-拉伸轴向疲劳实验，发现涂层合金的疲劳裂纹萌发机制对应力敏感，在S-N曲线上呈现出双重特征，这在以往的研究中从未报道过。当施加的应力高于临界应力时，涂层断裂引起的基体解离开裂是疲劳裂纹萌生的原因，导致疲劳裂纹源在界面出现。当施加的应力低于临界应力时，滑移台阶导致涂层断裂，在已经被位错堆积压住的脆性α相上形成额外的应力集中，从而加速了疲劳裂纹在亚表面的萌生。基于所提出的机制，引入了韧性铬夹层以降低涂层裂纹的速度，并吸收从基体脱落的位错，从而使涂层的开裂率的减少从40%增加到20%。本研究提出的机制将为设计硬质涂层提供理论指导，以减少对金属负载结构的疲劳寿命的不利影响，甚至改善基体的疲劳性能。

向上滑动阅览英文摘要

The presence of hard coatings can reduce the fatigue life of metal substrates to an unacceptable level, causing the catastrophic failure of load-bearing structures. Unfortunately, the present fatigue crack initiation mechanism is difficult to explain some existing experimental phenomena, and the preventive guidance theory remains absent. Here, by performing tension–tension axial fatigue experiments of TiN coated Ti-6Al-4V alloys, we found that the fatigue crack initiation mechanisms of the coated alloys were stress sensitive, showing two-fold characteristics in S–N curve, which was never reported in previous studies. As the applied stress higher than critical stress, coating fracture induced cleavage cracking of substrate is responsible for the fatigue crack initiation, leading to the fatigue crack source appear at the interface. As the applied stress lower than critical stress, slip step causes coating fracture, forming additional stress concentration on brittle α phase where has already been pressed by dislocations pile-up, thus accelerating fatigue crack initiation at the subsurface. Based on the proposed mechanisms, a ductile chromium interlayer was introduced to decrease coating crack velocity and absorb dislocations escaped from substrate, leading to the increase in the percentage reduction from 40% to 20%. The proposed mechanisms in this work will provide theoretical guidance for designing hard coatings to reduce detrimental effects on metal loading-structure's fatigue life to an acceptable level, even improving substrate's the fatigue properties.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117176

13. Revealing carbide precipitation effects and their mechanisms during quenching-partitioning-tempering of a high carbon steel: Experiments and Modeling

揭示高碳钢淬火-配分-回火过程中碳化物析出效应及其机理:实验与模拟

 

Jiazhi Zhang, Zongbiao Dai, Liyang Zeng, Xunwei Zuo, Jianfeng Wan, Yonghua Rong, Nailu Chen✉, Jian Lu✉, Hao Chen✉

Nailu Chen: nlchen@sjtu.edu.cn, 上海交通大学

Jian Lu: jianlu@cityu.edu.hk, 香港城市大学

Hao Chen: hao.chen@mail.tsinghua.edu.cn, 清华大学

https://doi.org/10.1016/j.actamat.2021.117176

 

摘要

淬火-配分-回火（Q-P-T）工艺，作为淬火和配分（Q&P）的改良工艺，是一种具有良好强度和延展性平衡的超高强度钢的处理工艺。 Q-P-T工艺的本质是在配分过程中通过碳从马氏体到奥氏体的分配来稳定亚稳态奥氏体，并在回火过程中通过微合金碳化物的纳米析出来强化马氏体基体。在配分-回火过程中，会发生碳偏析到位错、过渡碳化物析出和奥氏体分解等竞争性反应，这些反应将对Q-P-T钢的显微组织中发挥重要作用。在本研究中，通过各种工艺对Fe-0.67C-1.48Mn-1.53Si-0.038Nb钢的Q-P-T加工过程中的复杂组织演变进行了系统的表征。基于上述竞争性反应的考虑，建立了一个简明的具有双界面（马氏体/碳化物和马氏体/奥氏体）迁移的QPT-LE（局部平衡）热动力学模型来预测奥氏体分数及其碳含量的演变。这与CCE（受限碳平衡）热力学模型和QP-LE热动力学模型不同，在QPT-LE 模型中引入了碳化物析出的影响。因此，QPT-LE模型可以用来揭示碳化物析出对残余奥氏体分数及其碳含量的影响，而通过考虑碳偏析对位错的影响可以进一步提高碳化物分数的预测精度。总的来说，与流行的CCE模型和QP-LE模型相比，QPT-LE模型可以更好地预测实验结果。

向上滑动阅览英文摘要

Quenching-Partitioning-Tempering (Q-P-T), as a modified process of quenching and partitioning (Q&P), is a promising process to treat ultra-high strength steels with a good balance of strength and ductility. The essences of the Q-P-T process are to stabilize metastable austenite via carbon partitioning from martensite into austenite during partitioning and to strengthen the martensite matrix via nano-precipitation of micro-alloyed carbides during tempering. The competitive reactions, e.g. carbon segregation to dislocations, transition carbide precipitation and austenite decomposition, could occur during partitioning/tempering, which are expected to play a substantial role in the microstructures of the Q-P-T steels. In this contribution, the complex microstructure evolution during the Q-P-T processing of an Fe-0.67C-1.48Mn-1.53Si-0.038Nb steel was systematically characterized by various techniques. A concise QPT-LE (Local Equilibrium) thermo-kinetic model with dual interfaces (martensite/carbide and martensite/austenite) migration was established to predict the evolution of austenite fraction and its carbon content based on the consideration of competitive reactions mentioned above. In the QPT-LE model the effect of carbide precipitation is introduced, which is different from CCE (constrained carbon equilibrium) thermodynamic model and QP-LE thermo-kinetic model. Therefore, the QPT-LE model can be used to reveal the effects of carbide precipitation on the retained austenite fraction and its carbon content, while the prediction accuracy of carbide fraction can be further improved by considering the effect of carbon segregation to dislocation. In general, the QPT-LE model can better predict the experimental results compared with popular CCE model and QP-LE model.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117148

14. Insights into the selection mechanism of Widmanstätten growth by phase-field calculations

通过相场计算深入了解Widmanstätten生长的选择机制

 

H. Lebbad, B. Appolaire✉, Y. Le Bouar, A.Finel

B. Appolaire: benoit.appolaire@univ-lorraine.fr

https://doi.org/10.1016/j.actamat.2021.117148

 

摘要

本研究用相场计算研究了金属合金中Widmanstätten 结构的生长。结果表明，与剪切主导的转变相关的弹性能各向异性足以在恒定过饱和度下产生具有恒定伸长率的板状或针状析出物。进一步结果表明，即使在考虑到弹性的情况下，Ivantsov分析解决方案仍然可以很好地估计尖端周围扩散通量。仔细的分析表明，对于剪切主导的转变，（i）伸长方向位于由弹性核的最小值之一决定的习惯平面内；（ii）尖端形状和尺寸是平衡特征 ，由弹性力驱动，而不是像通常假设的那样由动态决定；（iii）针状析出物的尖端尺寸可以通过伸长方向的弹性核的取值来合理化。

向上滑动阅览英文摘要

We investigate the growth of Widmanstätten structures in metallic alloys with phase field calculations. We show that elastic energy anisotropy associated with shear dominated transformations is alone sufficient to give rise to plate or needle like precipitates with constant lengthening rates at constant supersaturations. We show that Ivantsov analytical solutions still provide good estimates of the diffusion flux around tips even when elasticity is accounted for. A careful analysis demonstrates that, for shear dominated transformations, (i) the lengthening direction lies in the habit plane determined by one of the minima of the elastic kernel; (ii) the tip shape and size are equilibrium features, driven by elastic forces, rather than dynamically determined as usually assumed; (iii) the tip size of acicular precipitates can be rationalized by the value of the elastic kernel in the lengthening direction.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117177

15. Thermodynamics and design of nanocrystalline alloys using grain boundary segregation spectra

基于晶界偏析光谱的纳米晶合金热力学及设计

 

Malik Wagih, Christopher A. Schuh✉

Christopher A. Schuh: schuh@mit.edu

https://doi.org/10.1016/j.actamat.2021.11717

 

摘要

溶质在晶界（GBs）的偏析是稳定纳米晶合金的一个关键机制。迄今为止，设计和筛选纳米晶稳定性的标准方法使用了一种简化的表示，将GB网络视为单一实体，因此，使用单一的 平均偏析能来表征合金中溶质GB偏析的特征。然而，这种简化没有捕捉到GBs的高度各向异性，这导致了偏析能量的光谱可能非常宽。本研究中我们消除了这种简化，并更正式地概述了正确的热力学标准，以筛选多晶结构的热力学稳定性，说明了 GBs的光谱性质。本研究继续应用所开发的标准来筛选超过200种基于嵌入原子方法潜力的合金组合。在其优点中，这种光谱方法能够严格执行热力学第三定律，而平均偏析能则不能。而且筛选的结果与实验观察结果基本一致。

向上滑动阅览英文摘要

Solute segregation at grain boundaries (GBs) is a key mechanism to stabilize nanocrystalline alloys. To date, the standard approach to design and screen for nanocrystalline stability uses a simplified representation that treats the GB network as a single entity, and thus, uses a single “average” segregation energy to characterize solute GB segregation in an alloy. This simplification, however, fails to capture the highly anisotropic nature of GBs, which results in a spectrum of segregation energies that can be very broad. Here, we remove this simplification, and outline more formally correct thermodynamic criteria to screen for thermodynamic stability of polycrystalline structures, accounting for the spectral nature of GBs. We proceed to apply the developed criteria to screen over 200 alloy combinations based on embedded atom method potentials. Among its benefits, this spectral approach enables strict enforcement of the third law of thermodynamics, where an average segregation energy does not. The results of the screening are in general agreement with experimental observations.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117149

16. Multiphase field modeling of grain boundary migration mediated by emergent disconnections

由断裂介导的晶界迁移的多相场模拟

 

Mahi Gokuli, Brandon Runnels✉

Brandon Runnels: brunnels@uccs.edu

https://doi.org/10.1016/j.actamat.2021.117149

 

摘要

有关晶界迁移的知识是理解和最终调节多晶材料特性的先决条件。来自实验和分子动力学（MD）模拟的证据表明，断裂的形成和运动是晶界迁移的一种机制。在本研究中晶界迁移是使用基于非凸边界能量的最小耗散势原理的多相场模型，以及断裂对的热成核的随机模型来建模的。在这个模型中，断裂在弹性驱动力的存在下自发产生，其运动介导了边界迁移。这种效应是由于断裂对的形成导致了应力集中，使弹性驱动力超过了阈值，并驱动断裂沿界面的扩展。该模型被应用于研究不同温度下单个断裂对的传播/湮灭、受扰动界面的弛豫以及剪切耦合。结果与目前对断裂的理解是一致的，并且捕捉到了热软化的影响。

向上滑动阅览英文摘要

Knowledge about grain boundary migration is a prerequisite for understanding and ultimately modulating the properties of polycrystalline materials. Evidence from experiments and molecular dynamics (MD) simulations suggests that the formation and motion of disconnections is a mechanism for grain boundary migration. Here, grain boundary migration is modeled using a multiphase field model based on the principle of minimum dissipation potential with nonconvex boundary energy, along with a stochastic model for thermal nucleation of disconnection pairs. In this model, disconnections arise spontaneously in the presence of an elastic driving force, and that their motion mediates boundary migration. The effect is due to the fact that the formation of the disconnections pairs results in a stress concentration, causing the elastic driving force to exceed the threshold value and driving the propagation of the disconnection along the interface. The model is applied to study the propagation/annihilation of single disconnection pairs, the relaxation of a perturbed interface, and shear coupling at various temperatures. The results are consistent with the current understanding of disconnections, and capture the effect of thermal softening.

 

 

ACTA

Vol. 217，15 Sep. 2021, 117180

17. On the origin of mosaicity in directionally solidified Ni-base superalloys

定向凝固镍基高温合金镶嵌现象的起源

 

Joel Strickland✉, Bogdan Nenchev, Karl Tassenberg, Samuel Perry, Gareth Sheppard, Hongbiao Dong, Ruiyao Zhang, Genoveva Burca, Neil D'Souza

Joel Strickland: joel_strickland@hotmail.co.uk

https://doi.org/10.1016/j.actamat.2021.117180

 

摘要

本文讨论了引起镶嵌性的小角度晶界的形成，这一现象最近才在单晶镍基超合金领域受到关注。在本文中，采用了先进的显微镜表征技术，从单晶涡轮叶片的横向截面上推断出枝晶的尖端生长动力学。等温曲率在诱导平行于凝固前沿的横向宏观偏析方面的作用已经成为可能。利用飞行时间能量分辨中子成像的晶体学数据和新的Bragg-dip后处理，建立了横向宏观偏析诱导小角度晶界，从而在单晶镍基超合金中产生了镶嵌性。镶嵌性与局部一次晶间距表现出良好的相关性，与那些生长速度较慢的枝晶相比，生长速度较慢的枝晶与铸造方向的<001>偏差更大。鉴于这些发现，本研究进一步讨论了镶嵌性的起源及其对二次晶粒形成的影响。

向上滑动阅览英文摘要

This article addresses the formation of low angle grain boundaries which give rise to mosaicity, a phenomenon that has only recently received attention in the single crystal Ni-base superalloy field. In this work, post-mortem advanced microscopy characterisation techniques are employed to deduce the dendrite tip growth kinetics from transverse sections of a single crystal turbine blade. As a result, it has been possible to highlight the role of isotherm curvature in inducing lateral macro-segregation parallel to a growing solidification front. Using crystallographic data from time-of-flight energy-resolved neutron imaging and novel Bragg-dip post processing, it is established that lateral macro-segregation induces small angle grain boundaries which gives rise to mosaicity within single crystal Ni-base superalloys. Mosaicity demonstrates good correlation with the local primary spacing, where faster growing dendrites demonstrate greater deviation of <001> from the casting direction, as compared with those growing at a slower rate. In light of these findings, the origin of mosaicity and its implication to secondary grain formation is discussed.