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金屬頂刊雙語導讀丨Acta Mater. Vol.214，1 Aug. 2021（上）

2021-08-29 來源：Goal Science

 

本期包含金屬材料領域論文10篇，涵蓋了鎂合金、珠光體等，國內科研單位包括南京工業大學等（通訊作者單位）。

 

Vol. 214 目錄

1. A quantitative study on mechanical behavior of Mg alloys with bimodal texture components

雙織構鎂合金力學行為的定量研究

 

2. Atomic diffusivities in amorphous and liquid Cu-Zr: Kirkendall effects and dependence on packing density

非晶態和液態Cu-Zr中的原子擴散速率研究：Kirkendall效應及其與堆垛密度的關系

 

3. Atomic insights on intermixing of nanoscale nitride multilayer triggered by nanoindentation

納米壓痕導致納米氮化物多層材料發生混合的原子尺度研究

 

4. Bridging microstructure and crystallography with the micromechanics of cleavage fracture in a lamellar pearlitic steel

組織和取向對片層珠光體鋼中解理斷裂微觀力學的影響

 

5. CALPHAD-informed phase-field modeling of grain boundary microchemistry and precipitation in Al-Zn-Mg-Cu alloys

基于CALPHAD的Al-Zn-Mg-Cu合金晶界成分和偏聚相場模擬

 

6. Characterizing the microstructural effect of build direction during solidification of laser-powder bed fusion of Al-Si alloys in the dilute limit: A phase-field study

Al-Si合金激光粉末熔煉凝固過程中制備方向對微觀組織影響的相場研究

 

7. Deep learning-based discriminative refocusing of scanning electron microscopy images for materials science

基于深度學習的掃描電子顯微鏡圖像失焦修復技術

 

8. Effect of size and orientation on stability of dislocation networks upon torsion loading and unloading in FCC metallic micropillars

FCC金屬微柱扭轉和卸載過程中微柱尺寸和取向對位錯網絡穩定性的影響

 

9. Enhanced microstructural stability of γ/γ’-strengthened Co-Ti-Mo-based alloys through Al additions

添加Al引起γ/γ′強化Co-Ti-Mo合金組織穩定性提高的機制研究

 

10. Faceting diagram for Ag segregation induced nanofaceting at an symmetric Cu tilt grain boundary

Ag偏聚誘導Cu中對稱傾側晶界形成納米面的機理研究

 

 

ACTA

Vol. 214，1 Aug. 2021, 117013

1. A quantitative study on mechanical behavior of Mg alloys with bimodal texture components

雙織構鎂合金力學行為的定量研究

 

Lingyu Zhao, Bo Guan, Yunchang Xin?, Xiaoxu Huang, Chenglu Liu, Peidong Wu, Qing Liu

Y. Xin：ycxin@cqu.edu.cn（南京工業大學）

https://doi.org/10.1016/j.actamat.2021.117013

 

摘要

對于單一織構鎂合金的力學和孿晶行為目前已有廣泛研究，而對于多織構鎂合金的研究則較少。我們對AZ31鎂合金棒材沿擠壓方向(ED)拉伸性能與<0002>// ED(19-87%)、<0002>⊥ED雙織構相對比例間的關系進行了系統的定量研究。研究表明，<0002>// ED織構有助于{10-12}孿晶，且是軟取向; 而<0002>⊥ED織構有助于棱柱滑移，且是硬取向。結果表明，屈服強度不隨軟取向占比增加線性下降，與混合定律計算結果存在偏差。當軟取向晶粒比例小于50%時，比例增加偏差增大；而當軟取向晶粒比例大于50%時，比例增加偏差減小。此外，抗拉強度似乎與軟取向占比沒有明顯關聯。基于以上結果，我們討論了相應機理并提對混合定律進行了修正。雙織構使得{10-12}孿晶變體能夠在較低的Schmid因子下激活，并且一個晶粒內能夠存在更多變體。傳統的應變調節理論無法解釋這種實驗現象。我們采用晶體塑性有限元對此進行了分析。結果表明，比起臨近晶粒的變形，孿晶變體間的相互作用對于孿晶的激活起到了更加重要的作用，這一發現為應變調節理論提供了重要補充。

向上滑動閱覽英文摘要

The mechanical and twinning behavior of Mg alloys containing a monolithic texture component have been extensively studied; however, studies on samples with multi texture components are much insufficient. In this study, the quantitative relationship between the mechanical behavior under tension along the extrusion direction (ED) of Mg AZ31 rods and the percentages of bimodal texture components <0002>// ED (19–87%) and <0002>⊥ED were systematically studied. The component <0002>// ED favors {10-12} twinning and is soft orientation; however, the component <0002>⊥ED favors prismatic slip and is hard orientation. The results show that the yield strength does not decrease linearly with an increase in the percentage of the soft orientations and show a deviation from the calculations using the conventional rule of mixtures. A higher percentage of the soft grains increases this deviation when the percentage is below 50%, and decreases it over 50%. The ultimate strengths, however, do not show an obvious dependence on the percentage of the soft orientations. Subsequently, the corresponding mechanisms are discussed and a modified rule of mixtures was developed. Bimodal texture components stimulate the activation of {10-12} twin variants with a low Schmid factor and the presence of more variants within one grain. Conventional strain accommodation rule was used to analyze this twinning behavior, but it cannot explain the experimental observations. Crystal-plasticity based finite element modeling was employed to analyze this strange twinning behavior. The results indicate that the interaction among twin variants, rather than deformation in neighboring grains, plays a major role in the activation of twins with a low Schmid factor, due to a hard deformation propagation from the soft grains to the hard grains. This finding provides an important complementation to the strain accommodation theory.

 

 

ACTA

Vol. 214，1 Aug. 2021, 116993

2. Atomic diffusivities in amorphous and liquid Cu-Zr: Kirkendall effects and dependence on packing density

非晶態和液態Cu-Zr中的原子擴散速率研究：Kirkendall效應及其與堆垛密度的關系

 

S.V. Ketov, Yu.P. Ivanov, B. Putz, Z. Zhang, J. Eckert, A.L. Greer?

A.L. Greer：alg13@cam.ac.uk

https://doi.org/10.1016/j.actamat.2021.116993

 

摘要

我們提出了一種創新性的測量非晶Cu-Zr在其玻璃態轉變溫度Tg附近原子互擴散率的方法。我們通過TEM和X射線能譜對濺射沉積多層薄膜的橫截面進行了表征。通過分析成分的演化推算得到了互擴散系數，結果其在Tg附近的值比預期的要高幾個數量級。非晶態和過冷態下層間界面的克根達爾漂移以及液相中的孔洞表明，銅的擴散系數遠大于鋯。眾所周知，非晶態Cu-Zr在特定成分處存在原子堆積密度極大值。本研究中的結果提供了直接證據，證明更加致密的堆積與較低的原子互擴散率有關。當銅擴散較慢時，互擴散速率也較慢。以上研究對于我們理解玻璃成型性和納米孔隙調控等問題具有重要幫助。

向上滑動閱覽英文摘要

A novel method for measurement of atomic interdiffusivity is applied to amorphous Cu-Zr close to its glass-transition temperature Tg. Sputter-deposited multilayers are examined in cross-section by transmission electron microscopy and energy-dispersive X-ray spectroscopy. Mapping the evolution of composition profiles gives the interdiffusivity, which is orders of magnitude higher than if coupled to the viscosity expected near Tg. Kirkendall drift of interlayer interfaces in both amorphous and supercooled liquid states (i.e. below and above Tg), and associated voiding in the liquid, show that the diffusivity of copper greatly exceeds that of zirconium. Amorphous Cu-Zr is known to show maxima in atomic packing density at sharply defined compositions. The comparison of the two compositions in the present work provides the first direct evidence that denser packing is associated with lower atomic interdiffusivity. The lower interdiffusivity is governed by a lower diffusivity of copper, and reflects a lessened degree of decoupling of the copper (fast) and zirconium (slow) diffusivities in an efficiently packed glass. The new insights help to understand issues ranging from glass-forming ability to the controlled generation of nanovoided structures.

 

 

ACTA

Vol. 214，1 Aug. 2021, 117004

3. Atomic insights on intermixing of nanoscale nitride multilayer triggered by nanoindentation

納米壓痕導致納米氮化物多層材料發生混合的原子尺度研究

 

Zhuo Chen, Yonghui Zheng, Lukas Löfler, Matthias Bartosik, Ganesh Kumar Nayak, Oliver Renk, David Holec, Paul H. Mayrhofer, Zaoli Zhang?

Z. Zhang：zaoli.zhang@oeaw.ac.at

https://doi.org/10.1016/j.actamat.2021.117004

 

摘要

納米多層涂層的力學性能與界面數量及其特性密切相關。當層厚降低時，一般而言材料的強度和韌性增加，但當層厚減小至只有幾納米時，性能下降。本研究中，我們發現了一種納米層壓入過程中的現象，可以一定程度上解釋材料性能的劣化。納米壓痕作為一種常見的涂層硬度表征手段，會導致多層結構產生一定程度的變形和破壞。我們通過SEM表征和原子尺度模擬，證明了納米壓痕會誘發外延過渡金屬氮化物超晶格薄膜的混雜。固溶體的形成降低了界面密度，使得位錯密度急劇下降。以上研究結果表明，塑性變形會引起氮化物多層結構的失穩，這對于我們進一步認識多層薄膜結構強度機制具有重要意義。

向上滑動閱覽英文摘要

Mechanical properties of nanoscale multilayer coatings are to a large extent governed by the number of interfaces and their characteristics. While for a reduced layer thickness, increasing strength and toughness values have been reported, properties degrade for layer thicknesses of just several nanometers. Here, we report on an entirely overlooked phenomenon occurring during the indentation of nanolayers, presumably explaining the degradation of properties. Nanoindentation, commonly used to determine properties of hard coatings, is found to disrupt and intermix the multilayer structure due to the deformation imposed. Detailed electron microscopy studies and atomistic simulations provide evidence for intermixing in an epitaxial transition metal nitride superlattice thin film induced by nanoindentation. The formation of a solid solution reduces the interfacial density and leads to a sharp drop in the dislocation density. Our results confirm that plastic deformation causes the microstructure instability of nitride multilayer, which may further improve our understanding of multilayer strength mechanisms.

 

 

ACTA

Vol. 214，1 Aug. 2021, 116988

4. Bridging microstructure and crystallography with the micromechanics of cleavage fracture in a lamellar pearlitic steel

組織和取向對片層珠光體鋼中解理斷裂微觀力學的影響

 

Rakesh Kumar Barik?, Abhijit Ghosh, Md. Basiruddin Sk, Sankalp Biswal, Amlan Dutta, Debalay Chakrabarti

R.K. Barik：barikrakesh4@gmail.com

https://doi.org/10.1016/j.actamat.2021.116988

 

摘要

本研究基于顯微組織和結晶學形貌，研究了全珠光體鋼在夏比沖擊實驗中的解理裂紋擴展。通過數學模型模擬，結合界面脫粘和裂紋逐步擴展機理，討論了珠光體片層取向對斷裂路徑影響。雖然珠光體鋼中較為常見的是{100}解理斷裂，但沿{110}晶面的裂紋擴展也可以在某些珠光體集落中普遍存在。這可能與層片界面對滑移的限制抑制了裂紋尖端的位錯發射有關。此外，珠光體組織中由于彈性模量或Schmid因子的不匹配而導致的應變不均是引起開裂的原因。我們基于斷裂力學和實驗觀測結果，提出了珠光體中不同類型裂脊形成的機制，闡明了片層取向在裂脊處晶體發生切變和彎曲過程中所起的作用。

向上滑動閱覽英文摘要

The present paper focuses on the microstructure-based cleavage crack propagation in a Charpy impact tested fully pearlitic steel by correlating microstructure and crystallography with the overall fracture behavior. The importance of pearlite lamellae orientation in providing preferred fracture paths is discussed, encompassing the mechanism of interface decohesion and stepwise crack propagation through a mathematical model simulation. While the {100} cleavage cracking is well familiar in pearlitic steels, crack propagation along the {110} crystallographic planes can also prevail in some pearlite colonies or nodules. This is related to suppressing the crack tip dislocation emissions due to restricted slip transferability across the lamellae interfaces. Besides, the strain incompatibility due to large elastic modulus or Schmid factor mismatch across the pearlite nodule boundaries is responsible for triggering internodular cracking in the steel. Connecting the framework of fracture mechanics with the experimental observations, the mechanisms pertaining to different types of tear ridges formed within a pearlite colony are proposed. This certainly illuminates the role of lamellae orientation in the process of crystal bending and shearing at the tear ridges formed within the colonies or at the twist nodule boundaries.

 

 

ACTA

Vol. 214，1 Aug. 2021, 116966

5. CALPHAD-informed phase-field modeling of grain boundary microchemistry and precipitation in Al-Zn-Mg-Cu alloys

基于CALPHAD的Al-Zn-Mg-Cu合金晶界成分和偏聚相場模擬

 

Chuanlai Liu?, Alistair Garner, Huan Zhao, Philip B. Prangnell, Baptiste Gault, Dierk Raabe, Pratheek Shanthraj?

C. Liu：c.liu@mpie.de

P. Shanthraj：pratheek.shanthraj@manchester.ac.uk

https://doi.org/10.1016/j.actamat.2021.116966

 

摘要

高強Al-Zn-Mg-Cu合金的晶界化學成分和析出行為對其力學和電化學性能有重要影響。模擬這類合金中的晶界偏聚、析出和溶質配分需要對這一體系的熱力學和動力學進行準確描述。目前開發的CALPHAD數據庫能夠較好地實現復雜多組分系統中的平衡態熱力學計算，且能夠和擴散模擬進行結合。本研究中，我們將CALPHAD數據庫和相場模型進行了結合，以求實現對合金熱處理過程中的非平衡過程進行準確模擬。特別地，我們在一種成分接近AA7050的Al-Zn-Mg-Cu模型合金中，系統研究晶界偏聚、晶界擴散、析出密度和遠場基體成分對晶界處η相析出長大的影響。結果表明，在時效早期階段，晶界的溶質分布極不均勻性，受η析出分布影響很大。在過時效過程中，Mg和Cu在晶界處存在顯著偏聚，而Zn則會迅速貧化。這種晶界偏聚顯著影響了析出形貌，但對晶界析出整體動力學的影響則相對有限。此外，晶界附近的溶質消耗很大程度上取決于Zn和Mg的擴散，這將影響時效早期無析出區的演化。我們將模擬結果與相似成分中掃描透射電子顯微鏡和原子探針的實驗結果進行了比較，兩者吻合較好。

向上滑動閱覽英文摘要

The grain boundary (GB) microchemistry and precipitation behaviour in high-strength Al-Zn-Mg-Cu alloys has an important influence on their mechanical and electrochemical properties. Simulation of the GB segregation, precipitation, and solute distribution in these alloys requires an accurate description of the thermodynamics and kinetics of this multi-component system. CALPHAD databases have been successfully developed for equilibrium thermodynamic calculations in complex multi-component systems, and in recent years have been combined with diffusion simulations. In this work, we have directly incorporated a CALPHAD database into a phase-field framework, to simulate, with high fidelity, the complex kinetics of the non-equilibrium GB microstructures that develop in these important commercial alloys during heat treatment. In particular, the influence of GB solute segregation, GB diffusion, precipitate number density, and far-field matrix composition, on the growth of a population of GB η-precipitates, was systematically investigated in a model Al-Zn-Mg-Cu alloy of near AA7050 composition. It is shown that the GB solute distribution in the early stages of ageing was highly heterogeneous and strongly affected by the distribution of GB η-precipitates. Significant Mg and Cu GB segregation was predicted to remain during overageing, while Zn was rapidly depleted. This non-trivial GB segregation behaviour markedly influenced the resulting precipitate morphologies, but the overall precipitate transformation kinetics on a GB were relatively unaffected. Furthermore, solute depletion adjacent to the GB was largely determined by Zn and Mg diffusion, which will affect the development of precipitate free zones during the early stages of ageing. The simulation results were compared with scanning transmission electron microscopy and atom probe tomography characterisation of alloys of the similar composition, with good agreement.

 

 

 

ACTA

Vol. 214，1 Aug. 2021, 116983

6. Characterizing the microstructural effect of build direction during solidification of laser-powder bed fusion of Al-Si alloys in the dilute limit: A phase-field study

Al-Si合金激光粉末熔煉凝固過程中制備方向對微觀組織影響的相場研究

 

Hossein Azizi?, Alireza Ebrahimi, Nana Ofori-Opoku, Michael Greenwood, Nikolas Provatas, Mohsen Mohammadi

H. Azizi：haziz@unb.ca, hossein.azizi@mail.mcgill.ca

https://doi.org/10.1016/j.actamat.2021.116983

 

摘要

激光粉末熔化(LPBF)增材制造相關研究表明，改變制備方向可以導致凝固組織形貌發生轉變，從而實現對材料織構和性能的調控。本研究中，我們通過數值模擬，研究了LPBF過程中制備方向對Al-Si合金組織演變的影響。我們建立了一個有限元熱場模型，以考慮垂直和水平打印過程中制備方向對熔池熱場特征的影響。隨后我們利用多參量相場模型對Al-Si合金的組織演變進行了研究。我們的相場模型可以自洽地模擬晶粒在添加孕育劑后的形核和形貌演變。我們通過對定向凝固Al-Si合金的形貌轉變數值檢測以及與Hunt的CET模型的比較，驗證了相場模型的準確性。相場模擬和晶粒分析結果表明，水平制備樣品中的形核速率和等軸晶比例更高，這與實驗觀測的結果一致。

向上滑動閱覽英文摘要

Additive manufacturing experiments using the laser powder bed fusion (LPBF) method reveal that changing the build direction can stimulate morphological transitions in the solidification microstructure. As a result, the final texture and material properties can be altered. In this work, we conduct numerical investigations to explore the effect of building direction on the microstructure evolution of dilute Al-Si alloy produced by the LPBF process. A finite element thermal model is developed to incorporate the effect of build direction on the thermal characteristics of the melt pool for a vertically and horizontally printed AlSi powder layer. We then utilize a multi-order parameter phase-field model to probe the microstructure evolution of LPBF Al-Si alloy in the dilute limit under the aforementioned thermal conditions for horizontal and vertical printing strategies. The phase-field model described here can self-consistently emulate spontaneous formation of nuclei from inoculant particles and simulate morphological transitions. The accuracy of the phase-field model is validated through the numerical examination of morphological transitions under directional solidification conditions of a dilute Al-Si alloy and compared to the predictions of the analytical CET theory of Hunt [1]. The phase-field simulations and subsequent grain analysis of the microstructure under transient thermal conditions reveal that the nucleation rate and hence equiaxed to columnar microstructure ratio is notably higher in the horizontally built samples. These results are in consistence with experimental observations.

 

 

ACTA

Vol. 214，1 Aug. 2021, 116987

7. Deep learning-based discriminative refocusing of scanning electron microscopy images for materials science

基于深度學習的掃描電子顯微鏡圖像失焦修復技術

 

Juwon Na?, Gyuwon Kim?, Seong-Hoon Kang?, Se-Jong Kim?, Seungchul Lee?

J. Na：juwonna7@postech.ac.kr

G. Kim：gyuwonkim96@postech.ac.kr

S.-H. Kang：kangsh@kims.re.kr

S.-J. Kim：ksj1009@kims.re.kr

S. Lee：seunglee@postech.ac.kr

https://doi.org/10.1016/j.actamat.2021.116987

 

摘要

掃描電子顯微鏡(SEM)在材料組織結構表征中被廣泛應用。但由于儀器狀態不佳或自動成像錯誤，圖像經常出現失焦，而研究人員需要對這些失焦圖像進行檢測恢復，以便進一步分析。我們提出了一種基于深度學習的掃描電鏡(SEM)圖像失焦修復方法，對于二次電子像(SE)效果尤其明顯。我們考慮了三個人工智能(AI)實際運用中的重要問題：(1) AI能否在人為設置條件下修復SEM圖像? (2) AI能否在無人為設置條件下修復SEM圖像？(3) AI在以上兩種情況下的修復是否有區別？為此我們通過單尺度卷積神經網絡、多尺度卷積神經網絡和數據增強多尺度卷積神經網絡逐步改進了算法，解決上述問題。研究表明，我們提出的方法不僅可以修復低質量的SEM圖像，而且還可以有區別地執行任務，這意味著修復是明確針對失焦區域進行的。我們采用馬氏體鋼和析出強化合金的SEM圖像對算法進行了驗證評價，并對深度學習修復的機制進行了解釋。以上結果有助于加快SEM的圖像采集速度，搭建材料信息化數據平臺。

向上滑動閱覽英文摘要

Scanning electron microscopy (SEM) has contributed significantly to the development of microstructural characteristics analysis in modern-day materials science. Although it is broadly utilized, out-of-focus SEM images are often obtained due to improper hardware adjustments and imaging automation errors. Therefore, it is necessary to detect and restore these out-of-focus images for further analysis. Here, we propose a deep learning-based refocusing method for SEM images, particularly secondary electron (SE) images. We consider three important aspects in which are critical for an artificial intelligence (AI)-based approach to be effectively applied in real-world applications: Can AI refocus SEM images on non-blind settings?, Can AI refocus SEM images on blind settings? and Can AI discriminately refocus SEM images on blind settings?. To infer these questions, we present progressively improved approaches based on convolutional neural networks (CNN): single-scale CNN, multi-scale CNN, and multi-scale CNN powered by data augmentation, to tackle each of the above considerations, respectively. We demonstrate that our proposed method can not only refocus low-quality SEM images but can also perform the task discriminately, implying that refocusing is conducted explicitly on out-of-focused regions within an image. We evaluate our proposed networks with SEM images of martensitic steel and precipitation-hardened alloy in qualitative and quantitative aspects and provide further interpretations of the deep learning-based refocusing mechanism. In conclusion, our study can significantly accelerate SEM image acquisition and is applicable to data-driven platforms in materials informatics.

 

 

 

ACTA

Vol. 214，1 Aug. 2021, 117010

8. Effect of size and orientation on stability of dislocation networks upon torsion loading and unloading in FCC metallic micropillars

FCC金屬微柱扭轉和卸載過程中微柱尺寸和取向對位錯網絡穩定性的影響

 

J.D. Gravell, S. Lee, S. Ryub, I. Ryu?

I. Ryu：ill.ryu@utdallas.edu

https://doi.org/10.1016/j.actamat.2021.117010

 

摘要

在連續的長度尺度上，金屬材料的力學性能受取向影響不大；然而當樣品尺寸減小到微米或納米尺度時，則經常表現出強烈的各向異性。本研究中，我們通過三維位錯動力學模擬研究了亞微米面心立方微柱在扭轉作用下塑性與取向的關系。我們基于原子尺度模擬結果，對我[001]、[101]和[111]三個取向上的表面形核進行了修正，重點關注了位錯微觀結構演化和加載/卸載時的各向異性力學響應的變化。模擬結果表明，在[101]和[111]取向的微柱中分別形成了共軸和六方網絡，使材料表現出良好的塑性回復，而[001]取向微柱中的矩形網絡則更穩定，因此塑性回復不顯著。

向上滑動閱覽英文摘要

At the continuum length scale, mechanical properties of metals show relatively weak orientation dependence; however, they exhibit strong anisotropic behaviors as the size of sample decreases to micron and nanometer length scales. In this study, three-dimensional dislocation dynamics (DD) simulations are performed to investigate the orientation-dependent plasticity in submicron face-centered cubic (FCC) micropillars subjected to torsion. Accommodating results from atomistic modeling, updated surface nucleation schemes in DD models have been developed for three orientations ([001], [101], and [111]), allowing investigation of the dislocation microstructure evolution and the corresponding anisotropic mechanical response upon torsional loading and unloading. The DD simulation results show that the coaxial and hexagonal networks formed in [101] and [111] oriented nanopillars, respectively, exhibited excellent plastic recovery, while the rectangular network formed in the [001] crystal orientation was more stable and did not experience as much plastic recovery.

 

 

ACTA

Vol. 214，1 Aug. 2021, 117011

9. Enhanced microstructural stability of γ/γ’-strengthened Co-Ti-Mo-based alloys through Al additions

添加Al引起γ/γ′強化Co-Ti-Mo合金組織穩定性提高的機制研究

 

Hye Ji Im, Won Seok Choi, KenHee Ryou, Jae Bok Seol, Tae Hyeok Kang, Won-Seok Ko?, Pyuck-Pa Choi?

W.-S. Ko：wonsko@ulsan.ac.kr

P.-P. Choi：p.choi@kaist.ac.kr

https://doi.org/10.1016/j.actamat.2021.117011

 

摘要

我們通過電子顯微鏡和密度泛函理論對多種不同成分γ/γ’ Co-Ti-Mo合金(Co-12Ti-4Mo, Co-12Ti-4Mo- 2Al, Co-12Ti-4Mo- 4Al, Co-10Ti-4Mo-2Al, Co-8Ti-4Mo-4Al at.%)的組織穩定性和高溫力學性能進行了研究。Co-12Ti-4Mo合金在800℃時效500 h后發生不連續析出，形成FCC (γ)和D019 (χ)相，而Co-12Ti-4Mo- 4al合金則依然維持γ/γ′組織。Al的添加通過在晶界形成L21 (β’)相，降低γ基體的過飽和度和FCC/L12的界面能，提高了γ/γ′組織的穩定性。Co-12Ti-4Mo-4Al合金的屈服強度低于無Al合金，但兩種合金間的差異隨溫度升高而減小。且與其他鈷基合金（如MarM302和Co-9Al-9W）相比，材料在高溫下屈服強度的顯著升高很大程度地抵消了這種下降的影響。

向上滑動閱覽英文摘要

We studied the microstructural stability and high-temperature mechanical properties of γ/γ’  Co-Ti-Mo based alloys of varying compositions (Co-12Ti-4Mo, Co-12Ti-4Mo-2Al, Co-12Ti-4Mo-4Al, Co-10Ti-4Mo-2Al, and Co-8Ti-4Mo-4Al (at.%)) using electron microscopy and density functional theory. The Co-12Ti-4Mo alloy underwent discontinuous precipitation into FCC (γ) and D019 (χ) phases after aging at 800°C for 500 h while the Co-12Ti-4Mo-4Al alloy maintained the γ/γ’ microstructure. Al additions improved the stability of the γ/γ’ microstructure by forming L21 (β’) precipitates along the grain boundaries, reducing the supersaturation of the γ matrix and the FCC/L12 interface energy. The Co-12Ti-4Mo-4Al alloy showed lower yield strength compared to the Al-free alloy, however, the difference in yield strength between these two alloys decreased with increasing temperature. This decrease is counterbalanced by a substantially enhanced specific yield strength at elevated temperatures as compared to other well-known Co-based alloys such as MarM302 and Co-9Al-9W.

 

 

 

ACTA

Vol. 214，1 Aug. 2021, 116960

10. Faceting diagram for Ag segregation induced nanofaceting at an symmetric Cu tilt grain boundary

Ag偏聚誘導Cu中對稱傾側晶界形成納米面的機理研究

 

Nicolas J. Peter?, Maria J. Duarte?, Christoph Kirchlechner?, Christian H. Liebscher?, Gerhard Dehm?

N.J. Peter：peter@mpie.de

M.J. Duarte：duarte@mpie.de

C. Kirchlechner：kirchlechner@mpie.de

C.H. Liebscher：liebscher@mpie.de

G. Dehm：dehm@mpie.de

https://doi.org/10.1016/j.actamat.2021.116960

 

摘要

本研究匯中，我們通過擴散偶實驗確定了Cu-Ag體系∑5非對稱傾側晶界處納米面的等溫演化。我們研究了銀濃度對沿晶界形成納米面的影響。等溫過程中，晶界分解為非對稱的貧銀部分和對稱的富銀(210)部分。Ag含量的增加將引起富Ag面段長度增加，而非對稱面長度保持不變?；谝陨蠈嶒灲Y果，我們建立了晶界納米面圖以闡明原子結構、Ag溶質過量和晶面傾斜狀態間的關系。

向上滑動閱覽英文摘要

In this work, we experimentally establish the isothermal nanofacet evolution at an asymmetric ∑5 tilt grain boundary in the Cu-Ag system using a diffusion couple approach. We investigate the nanofacet formation along the grain boundary in dependence of the Ag solute excess concentration. The initial grain boundary dissociates into asymmetric Ag-lean segments and Ag-rich symmetric (210) segments. Increasing Ag excess leads to an increase in Ag-rich facet segment length, while the length of the asymmetric facets remains constant. From this, we construct a grain boundary nanofaceting diagram deduced from our experiments relating local atomic structure, overall inclination and Ag solute excess.