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金属顶刊双语导读丨Scripta Mater. Vol.207, 15 Jan. 2022（下）

2021-12-11 来源：GS_Metals

 

本期包含金属材料领域论文13篇，涵盖了增材制造、镁合金、高温合金、马氏体等，国内科研单位包括西安交通大学、天津大学、中国科学院金属研究所等（通讯作者单位）。

 

Vol. 207 目录

1. Alloy design strategy for microstructural-tailored scandium-modified aluminium alloys for additive manufacturing

用于增材制造的微结构定制钪改性铝合金的合金设计策略

 

2. Influence of grain size and grain boundary misorientation on the fatigue crack initiation mechanisms of textured AZ31 Mg alloy

晶粒尺寸和晶界取向差对织构AZ31镁合金疲劳裂纹萌生机制的影响

 

3. Influence of the microstructural homogeneity on the high-temperature oxidation behavior of a single crystalline Ni-base superalloy

显微组织均匀性对镍基单晶高温合金高温氧化行为的影响

 

4. Enhancing reversible entropy change of all-d-metal Ni37.5Co12.5Mn35Ti15 alloy by multiple external fields

多外场增强全d金属Ni37.5Co12.5Mn35Ti15合金可逆熵变

 

5. Effect of microstructure heterogeneity on the mechanical properties of friction stir welded reduced activation ferritic/martensitic steel

显微组织异质性对搅拌摩擦焊还原活化铁素体/马氏体钢力学性能的影响

 

6. Hydrogen-assisted failure in Inconel 718 fabricated by laser powder bed fusion: The role of solidification substructure in the embrittlement

激光粉床熔化制造的Inconel 718氢辅助失效：凝固亚结构在脆化中的作用

 

7. Synthesis of high-entropy alloy thin films via grain boundary diffusion–assisted solid-state alloying

通过晶界扩散辅助固态合金化合成高熵合金薄膜

 

8. Deformation twinning-induced dynamic recrystallization during laser powder bed fusion

激光粉床熔融过程中变形孪晶诱导的动态再结晶

 

9. Mechanical response of the constrained nanostructured layer in heterogeneous laminate

异质层压板中受限纳米结构层的机械响应

 

10. Prediction of growth velocity of undercooled multicomponent metallic alloys using a machine learning approach

使用机器学习方法预测过冷多组分金属合金的生长速度

 

11. Martensitic transformation within nanotwins enhances fatigue damage resistance of a nanotwinned austenitic stainless steel

纳米孪晶内的马氏体相变增强了纳米孪晶奥氏体不锈钢的抗疲劳损伤能力

 

12. In situ transmission electron microscopy investigation of nucleation of GP zones under natural aging in Al-Zn-Mg alloy

Al-Zn-Mg合金自然时效下GP区形核的原位透射电镜研究

 

13. Grain boundary segregation and its implications regarding the formation of the grain boundary α phase in the metastable β-Titanium Ti–5Al–5Mo–5V–3Cr alloy

亚稳态β-钛Ti-5Al-5Mo-5V-3Cr合金中晶界偏析及其对晶界α相形成的影响

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114277

1. Alloy design strategy for microstructural-tailored scandium-modified aluminium alloys for additive manufacturing

用于增材制造的微结构定制钪改性铝合金的合金设计策略

 

D. Schimback✉, P. Mair, M. Bartl, F. Palm, G. Leichtfried, S. Mayer, P.J. Uggowitzer, S. Pogatscher

D. Schimback: david-erich.schimbaeck@airbus.com

https://doi.org/10.1016/j.scriptamat.2021.114277

 

摘要

为了充分发挥增材制造技术的潜力，有必要通过智能合金设计策略使材料适应工艺。为此，为了推导和研究各种材料概念，研究了Sc改性铝合金在激光粉末床熔合生产过程中的微观结构演变。添加Mg作为主要元素（Al-4.4Mg-0.8Sc-0.3Zr-0.5Mn）会产生双峰微观结构。相比之下，如果添加Cr作为主要元素（Al-2.6Cr-0.7Sc-0.3Zr），则外延晶粒生长会跨越多个焊道，从而产生明显的织构；添加Ti作为主要元素（Al-1Ti-1Sc-0.4Zr）会产生均匀的超细晶粒组织。这些微观结构之间的差异源于晶粒生长限制因素和溶质与初级沉淀结构的相互作用。因此，对关键冶金因素的精确控制产生了可以根据某些要求量身定制的新型材料。

向上滑动阅览英文摘要

To exploit the full potential of the additive layer manufacturing technique it is necessary to adapt the material to the process via a smart alloy design strategy. To this end, in order to derive and investigate various material concepts, the microstructural evolution of Sc-modified Al alloys was studied during the course of their production by laser powder bed fusion. Adding Mg as the main element (Al-4.4Mg-0.8Sc-0.3Zr-0.5Mn) generates an already-familiar bimodal microstructure. In contrast, if Cr is added as the main element (Al-2.6Cr-0.7Sc-0.3Zr), epitaxial grain growth takes place across several weld tracks, resulting in a distinct texture; and adding Ti as the main element (Al-1Ti-1Sc-0.4Zr) produces a uniform ultrafine-grained microstructure. The differences between these microstructures arise from interactions of the grain growth restriction factors and the solute with the primary precipitation structure. Thus, the precise manipulation of key metallurgical factors leads to novel materials which can be tailor-made for certain requirements.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114304

2. Influence of grain size and grain boundary misorientation on the fatigue crack initiation mechanisms of textured AZ31 Mg alloy

晶粒尺寸和晶界取向差对织构AZ31镁合金疲劳裂纹萌生机制的影响

 

Abbas Jamali, Anxin Ma, Javier LLorca✉

Javier LLorca: javier.llorca@upm.es

https://doi.org/10.1016/j.scriptamat.2021.114304

 

摘要

对织构AZ31B-O镁合金沿轧制方向进行完全反向、应变控制的循环变形，并在50次循环后（约占疲劳寿命的33%）分析变形和裂纹萌生机制。在2100个晶粒中的538个中发现了对应于金字塔滑移或拉伸孪晶的不同变形带。滑移轨迹分析表明，72.3%是锥体滑移带，18.4%是孪晶边界。仅在9.1%的具有变形带的晶粒中发现了金字塔滑移和孪晶。50次循环后裂纹普遍存在。在约15%的小晶粒（< 20 µm）中发现了晶界裂纹，它们主要与大角度晶界（>40º）相关。还发现裂纹是由平行于大晶粒（>45 µm）的金字塔滑移带或孪晶界的穿晶裂纹引起的。大多数（>60%）大晶粒在50次循环后出现穿晶裂纹。

向上滑动阅览英文摘要

The deformation and crack initiation mechanisms were analyzed in a textured AZ31B-O Mg alloy subjected to fully-reversed, strain-controlled cyclic deformation along the rolling direction after 50 cycles (approximately 33% of the fatigue life). Distinct deformation bands corresponding to pyramidal slip or tensile twins were found in 538 grains out of 2100 grains. Slip trace analysis showed that 72.3% were pyramidal slip bands and 18.4% were twin boundaries. Both pyramidal slip and twinning was only found in 9.1% of the grains with deformation bands. Cracking was widespread after 50 cycles. Grain boundary cracks were found in ≈15% of the small grains (< 20 µm) and they were mainly associated with high angle grain boundaries (>40º). Cracking was also found to occur by transgranular cracks parallel to the pyramidal slip bands or twin boundaries in large grains (>45 µm). The majority (>60%) of these large grains presented transgranular cracks after 50 cycles.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114224

3. Influence of the microstructural homogeneity on the high-temperature oxidation behavior of a single crystalline Ni-base superalloy

显微组织均匀性对镍基单晶高温合金高温氧化行为的影响

 

J. Pistor✉, S.P. Hagen✉, S. Virtanen✉, C. Korner✉

J. Pistor: julian.pistor@fau.de

S.P. Hagen: sebastian.p.hagen@fau.de

S. Virtanen: virtanen@ww.uni-erlangen.de

C. Korner: carolin.koerner@fau.de

https://doi.org/10.1016/j.scriptamat.2021.114224

 

摘要

通过选择电子束熔化（SEBM）进行的增材制造最近被证明是一种用于生产CMSX-4单晶（SX）镍基高温合金的有趣技术。本研究的目的是比较SX SEBM样品与由Bridgman熔模铸造获得的传统试样的高温抗氧化性。因此，TGA重量分析在850和1050 °C下在空气中进行100小时。由于在氧化之前进行固溶退火，在SEBM试样中，凝固引起的元素偏析可以完全均匀化，而对于传统试样仍然很明显。由于残留元素偏析，在氧化过程中出现了不均匀的氧化皮，在枝晶区域表现出高于平均水平的氧化皮厚度。因此，在存在偏析的情况下，TGA显示出更高的质量增加。总之，对于均质SEBM样品观察到更好的高温抗氧化性。

向上滑动阅览英文摘要

Additive manufacturing by means of selective electron beam melting (SEBM) was recently demonstrated as an intriguing technique for the generation of single crystalline (SX) CMSX-4, a commercial Ni-base superalloy. The objective of this study is to compare the high-temperature oxidation resistance of SX SEBM-samples to their conventional counterparts which are derived by Bridgman investment casting. Therefore, time-resolved isothermal gravimetric analysis (TGA) was conducted at 850 and 1050 °C in synthetic air for 100 h. Due to solution annealing prior to oxidation, solidification induced elemental segregations could be homogenized completely in case of the SEBM-material, whereas they remained apparent for the conventional Bridgman samples. With residual elemental segregations inhomogeneous oxide scales emerged during exposure, exhibiting above-average scale thicknesses upon dendritic regions. Consequently, TGA revealed a higher mass gain in case of present segregations. In conclusion, a better high temperature oxidation resistance is observed for the homogeneous SEBM material.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114303

4. Enhancing reversible entropy change of all-d-metal Ni37.5Co12.5Mn35Ti15 alloy by multiple external fields

多外场增强全d金属Ni37.5Co12.5Mn35Ti15合金可逆熵变

 

Yao Liu✉, Andong Xiao, Tianzi Yang, Zhitong Xu, Xianglong Zhou, Tianyu Ma✉

Yao Liu: liuyao12@xjtu.edu.cn （西安交通大学）

Tianyu Ma: matianyu@xjtu.edu.cn （西安交通大学）

https://doi.org/10.1016/j.scriptamat.2021.114303

 

摘要

引入多个外场增强全d金属Ni37.5Co12.5Mn35Ti15合金的可逆熵变。研究表明，对于0.01到5 T的磁场变化，可逆熵变可以从8.9大幅增加到24.1 J kg-1K-1。透射电镜对Ni37.5Co12.5Mn35Ti15结构转变的研究表明，磁结构转变温度随着磁场的变化以-1.4K T-1的速率降低，并随着静水压力以+5K k bar-1 的速率增加，从而为促进多场循环下的可逆熵变提供了条件。

向上滑动阅览英文摘要

The multiple external fields have been introduced to enhance the reversible entropy change of all-d-metal Ni37.5Co12.5Mn35Ti15 alloy. Our studies reveal that the reversible entropy change can be largely increased from 8.9 J kg−1K−1 to 24.1 J kg−1K−1 for a magnetic field change of 0.01 T to 5 T. The combined investigations of structural transition by transmission electron microscopy and magneto-strain reveal a strong coupling between magnetism and volume in the alloy, due to which, the magneto-structural transition temperature of Ni37.5Co12.5Mn35Ti15 decreases with the magnetic field by a rate of -1.4K T−1, and increases with the hydrostatic pressure by a rate +5K kbar−1, thus providing the condition for the promotion of reversible entropy change under multiple fields cycling.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114306

5. Effect of microstructure heterogeneity on the mechanical properties of friction stir welded reduced activation ferritic/martensitic steel

显微组织异质性对搅拌摩擦焊还原活化铁素体/马氏体钢力学性能的影响

 

Shengli Li, Napat Vajragupta, Abhishek Biswas, Wenshen Tang, Hao Wang, Aleksander kostka, Xinqi Yang✉, Alexander Hartmaier

Xinqi Yang: xqyang@tju.edu.cn （天津大学）

https://doi.org/10.1016/j.scriptamat.2021.114306

 

摘要

本文研究了搅拌摩擦焊还原活化铁素体/马氏体钢不同区域的显微硬度分布，并通过电子背散射分析将其与各个区域的分级马氏体显微组织相关联。结果表明，搅拌摩擦焊过程中不同亚区的原始奥氏体晶粒尺寸、包块尺寸和宽度的变化受峰值温度和有效应变速率的影响。显微硬度的分布与在不同区域观察到的几何必要位错密度直接相关。

向上滑动阅览英文摘要

The microhardness distribution in the different zones of a friction stir welded reduced activation ferritic/martensitic steel has been investigated and correlated to the hierarchical martensitic microstructure in the respective zones, characterized by electron backscatter diffraction orientation analysis. It is found that the variation of prior austenite grain size, packet size, and block width in different subzones is influenced by the peak temperature and effective strain rate during the friction stir welding process. The distribution of the microhardness correlates directly with the geometrically necessary dislocation density observed in the different zones.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114308

6. Hydrogen-assisted failure in Inconel 718 fabricated by laser powder bed fusion: The role of solidification substructure in the embrittlement

激光粉床熔化制造的Inconel 718氢辅助失效：凝固亚结构在脆化中的作用

 

Dong-Hyun Lee✉, Yakai Zhao, Soo Yeol Lee, Dirk Ponge, Eric A. Jagle

Dong-Hyun Lee: dhlee@cnu.ac.kr

https://doi.org/10.1016/j.scriptamat.2021.114308

 

摘要

通过一系列拉伸实验研究了氢气对激光粉床熔融法制备的Inconel 718力学行为的影响。样品经过两种不同方式热处理，即直接实效（DA）和均匀化加实效（HA）。详细的微观结构表征表明，在DA样品中存在包括高密度位错和沉淀物的凝固亚结构，而HA样品没有这种亚结构。DA样品表现出相对较高的强度，但抗氢脆性较低。通过对氢辅助裂纹的统计分析，证明DA样品的严重氢脆是由于大部分氢辅助晶间裂纹是在没有滑移定位帮助的情况下发生的。这些结果是根据热处理后微观结构的变化及其对氢捕获位点的影响进行讨论的。

向上滑动阅览英文摘要

The influence of hydrogen on the mechanical behavior of Inconel 718 fabricated by laser powder-bed-fusion was investigated through a series of tensile experiments. Samples subjected to two different post-fabrication heat treatments, viz. direct aging (DA) and homogenization plus aging (HA), were tested. Detailed microstructural characterization showed that a solidification substructure including a high density of dislocations and precipitates prevails in the DA sample while the HA sample is free from such a substructure. The DA sample exhibited a comparatively higher strength, but a lower resistance to hydrogen embrittlement. By recourse to a statistical analysis of the hydrogen-assisted cracks, the severe hydrogen embrittlement of the DA sample was proven to be due to the significant portion of hydrogen-assisted intergranular cracks that occurred without the aid of slip localization. These results are discussed in terms of the changes in microstructure upon heat treatments, and their influences on the hydrogen trapping sites.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114302

7. Synthesis of high-entropy alloy thin films via grain boundary diffusion–assisted solid-state alloying

通过晶界扩散辅助固态合金化合成高熵合金薄膜

 

Seungjin Nam, Sang Jun Kim, Moon J. Kim, Manuel Quevedo-Lopez, Jun Yeon

Hwang, Eun Soo Park✉, Hyunjoo Choi✉

Eun Soo Park: espark@snu.ac.kr

Hyunjoo Choi: hyunjoo@kookmin.ac.kr

https://doi.org/10.1016/j.scriptamat.2021.114302

 

摘要

在这项工作中，通过Al6(CoCrFeNi)94多层膜的固态合金化成功合成了具有面心立方结构的CoCrFeNi基固溶体高熵合金薄膜，并通过优化Al含量以防止任何氧化反应。系统地研究了多层薄膜中的微观结构和相演变，以了解合金化行为。有趣的是，合金元素可以扩散到薄膜层中，即使是那些具有非连接界面的层，这是由于纳米结构柱状晶粒的存在，可通过晶界发生扩散。因此，这些晶界充当合金元素的扩散路径网络，在整个多层膜中均质化并形成反应相，而不管热力学和动力学的预测如何。因此，晶界扩散辅助固态合金化可用于通过仅控制多层膜中的层厚度来合成用于各种多组分合金系统的高熵合金薄膜。

向上滑动阅览英文摘要

Herein, CoCrFeNi high-entropy alloy thin films were successfully synthesized via solid-state alloying from Al6(CoCrFeNi)94 multilayer films, forming a CoCrFeNi-based solid solution phase with a face-centered cubic structure by optimizing Al content to prevent any oxide reaction. The microstructural and phase evolutions in the multilayer films were systematically investigated to understand the alloying behavior. Interestingly, it can be evaluated that the alloying elements could be diffused into layers, even those with nonconnected interfaces, through the grain boundaries owing to the presence of nanostructured columnar grains. Thus, these grain boundaries act as a network of diffusion paths for alloying elemental atoms to be homogenized throughout multilayer films and form the reactive phase regardless of the thermodynamic and kinetic prediction. Consequently, grain boundary diffusion–assisted solid-state alloying can be used to synthesize high-entropy alloy thin films for various multicomponent alloy systems by only controlling the layer thickness in multilayer films.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114307

8. Deformation twinning-induced dynamic recrystallization during laser powder bed fusion

激光粉床熔融过程中变形孪晶诱导的动态再结晶

 

Hossein Eskandari Sabzi, Xiao-Hui Li, Chi Zhang, Hanwei Fu, David San-Martin, Pedro E.J. Rivera-Diaz-del-Castillo✉

Pedro E.J. Rivera-Diaz-del-Castillo: p.rivera1@lancaster.ac.uk

https://doi.org/10.1016/j.scriptamat.2021.114307

 

摘要

在使用各种工艺参数制造奥氏体不锈钢的激光粉床融合（LPBF）过程中观察到纳米孪晶的形成。透射电镜被用来去揭示这种孪晶的本质，这是由于LPBF固有的高应变快速凝固而形成的。动态再结晶（DRX）在LPBF期间也被激活，并由变形纳米孪晶诱导。同时，提出了一个恒温模型来确定孪生诱导DRX的临界条件，并通过实验结果验证了该模型。这种建模方法提供了一种对奥氏体不锈钢进行微观结构设计的方法，用于对高强度和延展性要求的应用。

向上滑动阅览英文摘要

Nanotwin formation is observed during laser powder bed fusion (LPBF) of austenitic stainless steels fabricated with various process parameters. Transmission electron microscopy was employed to reveal the nature of such twins, which are formed due to the high strain rapid solidification inherent to LPBF. Dynamic recrystallization (DRX) was also activated during LPBF, and induced by the deformation nanotwins. A thermostatistical model is proposed to determine the critical conditions for twinning-induced DRX; the model is validated with the reported experimental results. This modelling approach offers a method to microstructurally engineer austenitic stainless steels for potential applications needing high strength and ductility.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114310

9. Mechanical response of the constrained nanostructured layer in heterogeneous laminate

异质层压板中受限纳米结构层的机械响应

 

Hanfei Wang, Yueguang Wei✉, Zhifu Zhao, ZHongya Lin, Fengjiao Guo, Qian Cheng, Chongxiang Huang✉, Yuntian Zhu

Yueguang Wei: weiyg@pku.edu.cn （北京大学）

Chongxiang Huang: chxhuang@scu.edu.cn （四川大学）

https://doi.org/10.1016/j.scriptamat.2021.114310

 

摘要

了解异质结构材料中组成区域的区域间相互作用所依赖的机械行为是基本但具有挑战性的。在这里，我们报告了对层压板中受粗晶粒Cu层约束的纳米结构Cu-10Zn层的机械响应的定量研究。纳米结构层表现出较大的均匀伸长率，适度的加工硬化，但逐渐降低了工程应力。这种独特的响应主要归因于层间约束，这导致形成分散的稳定应变带，从而使机械孪晶和堆垛层错广泛激活。这些发现为异质结构的变形和承载机制提供了新的见解。

向上滑动阅览英文摘要

Understanding the inter-zone interaction-dependent mechanical behavior of constituent zones in heterostructured material is fundamental but challenging. Here we report quantitative investigations on the mechanical response of a nanostructured Cu-10Zn layer constrained by coarse-grained Cu layers in a laminate. The nanostructure layer displays large uniform elongation, moderate work hardening but gradually reduced engineering stress. Such unique responses are primarily attributed to the inter-layer constraint, which leads to the formation of dispersed stable strain bands and thus enables extensive activation of mechanical twinning and stacking faults. These findings provide new insights into the deformation and load-bearing mechanisms of heterostructures.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114309

10. Prediction of growth velocity of undercooled multicomponent metallic alloys using a machine learning approach

使用机器学习方法预测过冷多组分金属合金的生长速度

 

Vanga Sreekar, Rahul M.R.✉, Gandham Phanikumar

Rahul M.R.: rahulmr@iitism.ac.in

https://doi.org/10.1016/j.scriptamat.2021.114309

 

摘要

建立过冷金属合金的生长动力学对于了解凝固过程中的微观结构演变至关重要。迄今为止，物理过程的复杂性已将增长模型限制为简单的假设，这些假设无法实现令人满意的预测能力。作过冷度函数的生长速度的实验测量也很乏味。目前的研究使用实验和文献数据来训练机器学习算法，训练了五种算法：Random Forest、Bagging Regressor、Gradient Boosting Regressor、XGBoost和Articial Neural Network。使用了910个标记数据集，其中70%的数据用于训练，30%的数据用于测试。ANN的R2交叉验证得分超过0.89。训练后的算法用于预测中高熵合金的生长速度，与实验数据具有良好的兼容性。

向上滑动阅览英文摘要

Establishing growth kinetics of undercooled metallic alloys is essential to understand microstructure evolution during solidification processing. The complexity of the physical processes have hitherto limited growth models to simple assumptions that do not lead to satisfactory predictive capability. Experimental measurements of growth velocity as a function of undercooling are also tedious. The current study uses experimental and literature data to train the machine learning algorithms. Five algorithms are trained: Random Forest, Bagging Regressor, Gradient Boosting Regressor, XGBoost, and Artificial Neural Network. A labeled data set of 910 was used, with 70% data for training and 30 % data for testing. An R2 cross-validation score of more than 0.89 was obtained for ANN. The trained algorithms are used to predict the growth velocity of medium and high entropy alloys show good compatibility with the experimental data.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114313

11. Martensitic transformation within nanotwins enhances fatigue damage resistance of a nanotwinned austenitic stainless steel

纳米孪晶内的马氏体相变增强了纳米孪晶奥氏体不锈钢的抗疲劳损伤能力

 

Q. Li, D.Y. Liu, F.K. Yan, N.R. Tao✉

N.R. Tao: nrtao@imr.ac.cn （中国科学院金属研究所）

https://doi.org/10.1016/j.scriptamat.2021.114313

 

摘要

我们研究了一种新型纳米孪晶316L不锈钢的低周疲劳行为，该不锈钢由嵌入基体中的具有特征位错排列的纳米孪晶奥氏体晶粒组成。我们发现，α\prime-马氏体转变被激活，横穿孪晶层，在高应变幅度下进行纳米孪晶晶粒的局部变形。这些α\prime-马氏体核主要来源于“锯齿形”滑移带和孪晶相交处。由于纳米孪晶内的α\prime-马氏体相变有效释放了局部应力/应变，同时提高了低周状态下的疲劳强度和疲劳寿命。

向上滑动阅览英文摘要

We investigated the low-cycle fatigue behavior of a novel nanotwinned 316L stainless steel consisting of nanotwinned austenitic grains embedded in the matrix with characteristic dislocation arrangements. We excitingly found that the α\prime-martensitic transformation is activated traversing twin lamellae to undertake the localized deformation of nanotwinned grains at high strain amplitudes. These α\prime-martensite nuclei are mainly originated from the intersections between “zigzag” slip bands and twin lamellae. Thanks to the effective release of stress/strain localization by the α\prime-martensitic transformation within nanotwins, the fatigue strength and fatigue life in the low-cycle regime are simultaneously enhanced.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114319

12. In situ transmission electron microscopy investigation of nucleation of GP zones under natural aging in Al-Zn-Mg alloy

Al-Zn-Mg合金自然时效下GP区形核的原位透射电镜研究

 

Arya Chatterjee✉, Liang Qi, Amit Misra

Arya Chatterjee: archatte@umich.edu

https://doi.org/10.1016/j.scriptamat.2021.114319

 

摘要

该研究表明，Al-Zn-Mg合金自然时效过程中非常早期（一小时内）的析出过程非常复杂，析出物类型和形成机制波动很大。在透射电子显微镜内进行原位加热，然后淬火和室温自然时效，以研究早期沉淀的形成和演变。研究表明，在非常早期的自然时效过程中，约2min形成溶质簇，随后在约10min时与溶质簇相邻的GP-II区成核。此外，发现GP-II的成核与GP-I相关，但不是一种独特的机制。观察到GP-I沉淀物通过“分离”成核（即从GP-I和Al基质之间的界面）或通过原位成核（即从GP-I沉淀物）形成GP-II的位点。有时可观察到一些GP-II沉淀物溶解在铝基体中，而没有进一步转化为ƞ'沉淀物。

向上滑动阅览英文摘要

This investigation reveals very early-stage (within an hour) precipitation during natural-aging of Al-Zn-Mg alloy can have very complex processes with strong fluctuations in precipitate types and formation mechanisms. In situ heating followed by quenching and subsequent natural-aging at room temperature was carried inside transmission electron microscope to study the formation and evolution of early-stage precipitation. Investigation reveals formation of solute clusters at ∼2 mins and subsequent nucleation of GP-II zone adjacent to clusters at ∼10 mins during very early-stage natural-aging. Moreover, nucleation of GP-II is found to be related to GP-I but not in one unique mechanism. GP-I precipitates were observed to act as sites for the formation of GP-II either by ‘separated’ nucleation (i.e. from the interface between GP-I and Al matrix) or via in situ nucleation (i.e. from a GP-I precipitate). Occasionally, some GP-II precipitates were observed to dissolve into Al matrix without further transforming to ƞ′ precipitates.

 

 

SCRIPTA

Vol. 207, 15 Jan. 2022, 114320

13. Grain boundary segregation and its implications regarding the formation of the grain boundary α phase in the metastable β-Titanium Ti–5Al–5Mo–5V–3Cr alloy

亚稳态β-钛Ti-5Al-5Mo-5V-3Cr合金中晶界偏析及其对晶界α相形成的影响

 

T.S. Prithiv, Zachary Kloenne, Dian Li, Rongpei Shi, Yufeng Zheng, Hamish L. Fraser, Baptiste Gault, Stoichko Antonov✉

Stoichko Antonov: s.antonov@mpie.de

https://doi.org/10.1016/j.scriptamat.2021.114320

 

摘要

我们研究了在β-钛合金Ti-5Al-5Mo-5V-3Cr-0.5Fe (wt.%)时效过程中形成的有害晶界α相的起源。采用电子显微镜和原子探针探测了淬火状态β中小角度和大角度晶界的组成。我们的分析揭示了，一些α相稳定元素在两种类型边界处的强烈偏析（尤其是氧）以及β相稳定元素的消耗。尽管存在这种局部成分偏析，晶界仍保持体心立方结构。我们基于测量的晶界成分的热力学计算表明，偏析显着增加了时效时α成核的化学驱动力。我们的工作为亚稳态β-Ti合金中沿β晶界形成的非必要晶界α层提供了重要见解，并为这些具有增强机械性能的合金的微观结构工程铺平了道路。

向上滑动阅览英文摘要

We investigated the origin of the deleterious grain boundary α phase formed during the aging of the β-titanium alloy, Ti–5Al–5Mo–5V–3Cr–0.5Fe (wt.%). We probed the composition of low and high-angle grain boundaries from the as-quenched β condition correlating electron microscopy and atom probe tomography. Our analysis reveals strong segregation of some α-stabilizing elements at both types of boundaries, especially oxygen, along with a depletion of β-stabilizing elements. The grain boundary maintains the body-centered-cubic structure despite the presence of this local composition. Our thermodynamic calculations, based on the measured grain boundary compositions, indicate that the segregation significantly increases the chemical driving force for α nucleation upon aging. Our work provides essential insight into the formation of the undesired grain boundary α layers along prior-β grain boundaries in metastable β-Ti alloys and paves the way for microstructural engineering of these alloys with enhanced mechanical properties.