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microstructure evolutions of Ni-Ti-Nb-Al alloys with different Al addition

JOURNAL OF ALLOYS AND COMPOUNDS 2017年 695卷 2923-2929页

作者： Wang, Cong Gao, Qiuzhi Yuan, Ying Zhang, Hailian Zhang, Jian Wang, Qiuyang Qu, Fu Northeastern Univ Qinhuangdao Sch Comp & Commun Engn Qinhuangdao 066004 Peoples R China Northeastern Univ Sch Mat Sci & Engn Shenyang 110819 Peoples R China Northeastern Univ Qinhuangdao Ctr Comp Qinhuangdao 066004 Peoples R China Yanshan Univ Sch Econ & Management Qinhuangdao 066004 Peoples R China

microstructure evolutions of Ni-Ti-Nb-Al alloys with different Al addition subjected to casting and solution-treatment have been investigated using scanning electron microscope (SEM) and X-ray diffraction (XRD). The alloys were prepared by vacuum arc melting, and then solution-treated at 1273 K for 20 h. The alloys with 3 at.% Al addition and Al-free show a microstructure consisting by B2-NiTi matrix phase and soft beta-Nb precipitate. With increasing Al addition, Al3Ti phase firstly forms, and Ni3Al only can be found in the 7 at.% Al alloy. The addition of Al promotes the diffusion of Nb during casting and solution-treatment, resulting in the refinement of beta-Nb precipitate. For the as-cast alloys, the macro-hardness values increase with the increase in Al content and slightly increase after solution-treatment. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Ni-Ti-Nb-Al alloys Casting Solution-treatment microstructure evolutions Macro-hardness

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REVIEW ON PHASE-FIELD MODELING OF microstructure evolutions: APPLICATION TO ELECTRON BEAM ADDITIVE MANUFACTURING

REVIEW ON PHASE-FIELD MODELING OF MICROSTRUCTURE EVOLUTIONS:...

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9th ASME International Manufacturing Science and Engineering Conference (MSEC2014)

作者： Sahoo, Seshadev Chou, Kevin Univ Alabama Dept Mech Engn Tuscaloosa AL 35487 USA

ISBN: (纸本)9780791845813

Powder-bed electron beam additive manufacturing (EBAM) is a relatively new technology to produce metallic parts in a layer by layer fashion by melting and fusing metallic powders. EBAM is a rapid solidification process and the properties of the parts depend on the solidification behavior as well as the microstructure of the build material. Thus, the prediction of part microstructures during the process may be an important factor for process optimization. Nowadays, the increase in computational power allows for direct simulations of microstructures during materials processing for specific manufacturing conditions. Among different methods, phase-field modeling (PFM) has recently emerged as a powerful computational technique for simulating microstructure evolutions at the mesoscale during a rapid solidification process. PFM describes microstructures using a set of conserved and non-conserved field variables and the evolution of the field variables are governed by Cahn-Hilliard and Allen-Cahn equations. By using the thermodynamics and kinetic parameters as input parameters in the model, PFM is able to simulate the evolution of complex microstructures during materials processing. The objective of this study is to achieve a thorough review of PFM techniques used in various processes, attempted for an application to microstructure evolutions during EBAM. The concept of diffuse interfaces, phase field variables, thermodynamic driving forces for microstructure evolutions and the kinetic phase-field equations are described in this paper.

关键词： Electron beam additive manufacturing (EBAM) microstructure evolutions Phase-field modeling Simulations

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Thermal aging effect on elevated temperature deformation mechanisms of 316L stainless steel weld metal by small punch test

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MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES microstructure AND PROCESSING 2025年 927卷

作者： Fan, Y. Hu, J. Y. Bian, W. W. Hu, Y. Cui, K. X. Shandong Univ Sch Energy & Power Engn Jinan 250061 Peoples R China Univ Sci & Technol Beijing Natl Ctr Mat Serv Safety Beijing 100083 Peoples R China Univ Sci & Technol China Hefei 230026 Peoples R China Int Acad Neutron Sci Shandong Key Lab Neutron Sci & Technol Qingdao 266199 Peoples R China Tsinghua Univ Dept Chem Engn Beijing Key Lab Membrane Mat & Engn Beijing 100084 Peoples R China

The effects of long-term thermal aging on the microstructural evolution and its elevated temperature deformation behavior of 316L stainless steel weld metal were studied using the small punch test at 350 degrees C. The mechanical responses at the microstructural scale were investigated to better understand the mechanism of the influence of long-term thermal aging on the mechanical properties of the 316L weld metal. The results indicated that the hardness and mechanical strength of the 316L weld metal increased slightly with extended thermal aging time at 400 degrees C, which was primarily attributed to spinodal decomposition and G-phase precipitation in the ferrite phase. The hardening of ferrite increased the deformation incompatibility between the ferrite and austenite phases. Slip bands were blocked at the phase interface, leading to preferential cracking along the phase interface. In contrast, in the as-received 316L weld metal, slip bands could extend between two phases by means of multisystem slip, and cracks tended to crack along austenite grain boundaries. Notably, the deformation mechanism of austenite phase exhibited significant changes due to long-term thermal aging. The as-received austenite deformed through dislocation slip and twinning due to its lower stacking fault energy. After long-term thermal aging, the primary mechanisms governing the plastic deformation of austenite shifted to cross slip and multiple slip. In addition, a smaller dislocation cell structure (about 200 nm) was formed in the deformed austenite after long-term thermal aging, compared to a larger dislocation cell structure (about 500 nm) in the deformed austenite before aging. In contrast, the deformation mechanism of the ferrite phase in the 316L weld metal remained consistent, dominated by slip deformation both before and after long-term thermal aging.

关键词： 316L weld metal Thermal aging microstructure evolutions Deformation behavior Small punch test

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Catalytic mechanisms of nickel nanoparticles for the improved dehydriding kinetics of magnesium hydride

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Journal of Magnesium and Alloys 2024年第10期12卷 4278-4288页

作者： Shuaijun Ding Yuqing Qiao Xuecheng Cai Congcong Du Yixuan Wen Xun Shen Lidong Xu Shuang Guo Weimin Gao Tongde Shen Clean Nano Energy Center State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao066004China Hebei Key Laboratory of Applied Chemistry College of Environmental and Chemical EngineeringYanshan UniversityQinhuangdao 066004China Department of Mechanical Engineering The University of Hong KongPokfulam RoadHong KongChina Deakin University GeelongInstitute for Frontier MaterialsLocked Bag 20000VIC3220Australia

MgH_(2),albeit with slow desorption kinetics,has been extensively studied as one of the most ideal solid hydrogen storage *** such catalyst as Ni can improve the desorption kinetics of MgH_(2),whereas the catalytic role has been attributed to different substances such as Ni,Mg_(2)Ni,Mg_(2)NiH0.3,and Mg_(2)*** the present study,Ni nanoparticles(Ni-NPs)supported on mesoporous carbon(Ni@C)have been synthesized to improve the hydrogen desorption kinetics of MgH_(2).The utilization of Ni@C largely decreases the dehydrogenation activation energy from 176.9 to 79.3 kJ mol^(−1) and the peak temperature of dehydrogenation from 375.5 to 235℃.The mechanism of Ni catalyst is well examined by advanced aberration-corrected environmental transmission electron microscopy and/or x-ray *** the first dehydrogenation,detailed microstructural studies reveal that the decomposition of MgH_(2)is initially triggered by the Ni-NPs,which is the rate-limiting ***,the generated Mg reacts rapidly with Ni-NPs to form Mg_(2)Ni,which further promotes the dehydrogenation of residual MgH_(2).In the following dehydrogenation cycle,Mg_(2)NiH4 can rapidly decompose into Mg_(2)Ni,which continuously promotes the decomposition of MgH_(2).Our study not only elucidates the mechanism of Ni catalyst but also helps design and assemble catalysts with improved dehydriding kinetics of MgH_(2).

关键词： Hydrogen storage materials Magnesium hydride Ni nanoparticles Microscopic catalytic process microstructure evolutions

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Quantitative analysis and comparison on densification kinetics and grain growth mechanisms using reactively and directly densified TiB2-SiC-hBN ceramics

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JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 2024年第8期44卷 4863-4874页

作者： Liang, Huayue Zou, Ji Liu, Jingjing Ji, Wei Wang, Weimin Fu, Zhengyi Wuhan Univ Technol State Key Lab Adv Technol Mat Synth & Proc Wuhan 430070 Peoples R China Wuhan Univ Technol Hubei Longzhong Lab Wuhan 441000 Peoples R China Wuhan Univ Technol Sch Mat Sci & Engn Wuhan 430070 Peoples R China

Compared to samples sintered from directly mixed powders, reactive sintering enables the production of denser ceramic materials with finer grains at even lower temperatures. However, there is a lack of quantitative comparisons between the two sintering approaches in terms of densification mechanisms and grain growth kinetics. In this work, taking two types of TiB2-SiC-hBN ceramics sintered from raw powders containing TiB2, SiC and hBN (TSB -M) and TiN, Si and B4C (TSB -R) as model materials, above mechanisms were quantitatively investigated using spark plasma sintering. Effects of dwell temperature and sintering pressure on the microstructure evolutions, densification kinetics as well as grain growth of TSB -R and TSB -M were thoroughly examined. The densification mechanisms for both samples under different conditions were revealed by calculating the effective stress exponent and apparent activation energy. According to regression coefficients for different grain growth exponents, the dominated growth mechanisms for SiC and TiB2 grains were also explored.

关键词： Reactive sintering Spark plasma sintering microstructure evolutions Densification kinetics Grain growth mechanisms

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Nitriding high entropy alloy films: Opportunities and challenges

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SURFACE & COATINGS TECHNOLOGY 2024年 476卷

作者： Wu, Xinmeng Xu, Xin Jiang, Yaohong Chen, Chunyan Han, Haiwei Zhao, Lijun Xu, Junhua Yu, Lihua Jiangsu Univ Sci & Technol Sch Mat Sci & Engn Zhenjiang 212000 Peoples R China

High entropy nitride (HEN) films have attracted much attention due to their versatile properties, such as satisfactory mechanical properties, excellent anti-oxidation performance, outstanding corrosion resistance, and vitally important thermostability, indicating high application potentials. This paper reviews the four core effects and discusses several empirical parameters for phase prediction in HEAs. Then, this review focuses on the recent developments of HEN films, introducing how N contents as well as other factors influences the microstructures and thus leads to changes in relevant properties, such as mechanical, tribological, and chemical stabilities, what follows is the related mechanisms contributing to. Lastly, future trends and outlooks are briefly introduced. This review is aimed to give a comprehensive introduction to recent developments in HEN films, and to make it convenient to explore the research gaps for students and researchers.

关键词： High entropy alloys Core effects Nitride films microstructure evolutions Versatile properties

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Tensile/compression creep aging behavior of 2195-T34 Al-Li alloy under different stress levels

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MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES microstructure AND PROCESSING 2025年 935卷

作者： Chen, F. Huang, Y. J. Wang, H. Jiang, Y. N. Zeng, Q. Q. Ningbo Univ Coll Sci & Technol Sch Mech Engn & Automat Ningbo 315300 Peoples R China Cent South Univ Sch Mech & Elect Engn Changsha 410083 Peoples R China Zooml Heavy Ind Sci & Technol Dev Co Ltd Changsha 410000 Peoples R China

Typically, the influence of compressive stress has been seldom considered during the creep aging process (CAF) of thin-walled components. However, the inclusion of stiffener is known to greatly enhance the compressive stress during CAF, and the influence of compressive stress cannot be ignored. In this work, the tensile creep aging (TCA) and compressive creep aging (CCA) behavior and microstructure evolution were investigated under varying stresses, employing the 2195-T34 Al-Li alloy as the target material. A statistical analysis reveals a disparity in the creep strains of TCA and CCA. Under reduced stress conditions, the creep strain of the former exceeds that of the latter, and the degree of asymmetry gradually decreases as stress levels increase. The asymmetry in the strength of the creep-aged specimens was also observed, with the TCA specimens exhibiting more strength than the CCA specimens and the asymmetry in strength decreased with increasing stress. The stress exponents of TCA and CCA were determined to ben = 0.88 and n = 2.23 respectively, and the creep mechanisms of the two specimens exhibited distinct differences. Microstructural analysis revealed a more pronounced Cu-rich phase at the grain boundaries of the TCA specimens, leading to a reduction in the elongation of the specimens, which was confirmed by differences in fracture morphology. The CCA specimens had a higher concentration of theta ' phases, and the number of these phases declined as the stress increased, which is consistent with the result that the strength of the CCA specimens improved with increasing stress. Furthermore, a constitutive model derived from tensile/compression creep curves is proposed, and the calculated results and actual data exhibit remarkable agreement.

关键词： Al-Li alloy Tensile/compression stress Creep aging microstructure evolutions Constitutive modeling

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Addressing the strength-ductility trade-off in a cast Al-Li-Cu alloy—Synergistic effect of Sc-alloying and optimized artificial ageing scheme

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Journal of Materials Science & Technology 2022年第1期96卷 212-225页

作者： Jinshuo Zhang Guohua Wu Liang Zhang Xiaolong Zhang Chunchang Shi Xin Tong National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composites School of Materials Science andEngineeringShanghai Jiao Tong UniversityShanghai200240China Shanghai Innovation Institute for Materials Shanghai200444China

A dramatic improvement of strength and ductility of cast Al-2.5Li-1.5Cu-1Zn-0.5Mg-0.15 Zr alloy was obtained by the collaboration of Sc-alloying and optimized ageing *** and independent influence of Sc-alloying and different ageing temperatures were *** results revealed that a substantial increase was realized in the hardness of Sc-containing alloy,and the ageing response time was only influenced by ageing *** and heterogeneousδ'(Al_(3)Li),wideδ'-precipitation free zones(δ'-PFZs),and a large amount of T_(1)(Al_(2)CuLi)precipitates were observed in Sc-containing alloy aged at 175℃,which resulted in superior yield strength and poor *** Sc-containing alloy obtained an excellent combination of ductility(elongation=8.2%)and tensile strength(ultimate strength=565 MPa)suffered to 150℃ ageing for 64 *** increase in the elongation was mainly due to the combined effect of grain refining,much finerδ',and extremely narrowδ'-PFZs(<10 nm),while the higher strength was mainly attributed to the formation of Al_(3)(Sc,Zr,Li)composite particles and a large amount of S'(Al_(2)CuMg)***,the enhancement of the different ageing temperature(150℃ and 175℃)on the mechanical properties of the alloys without Sc addition was not obvious.

关键词： Cast Al-Li-Cu alloy δ’-PFZs Mechanical properties Cu-containing phases microstructure evolutions

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Cavitation abrasive integrated waterjet peening process and the effect of process parameters on the surface integrity of TA19 titanium alloy

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SURFACE & COATINGS TECHNOLOGY 2022年 440卷 1页

作者： Yao, Shulei Wang, Gongyu Li, Kaishang Wang, Ning Zhang, Chengcheng Liu, Shuang Liu, Changli Zhang, Xiancheng Tu, Shantung East China Univ Sci & Technol Key Lab Pressure Syst & Safety Minist Educ Shanghai 200237 Peoples R China AECC Commercial Aircraft Engine Co Ltd Shanghai Engn Res Ctr Commercial Aircraft Engine Shanghai 201108 Peoples R China East China Univ Sci & Technol Sch Mech & Power Engn Key Lab Pressure Syst & Safety Minist Educ Meilong Rd 130 Shanghai 200237 Peoples R China

Waterjet peening has emerged as a potential surface treatment technology, which is gradually being used to improve the surface integrity and mechanical behavior of metal materials. Submerged abrasive waterjet peening, which combines cavitation peening and abrasive waterjet peening and called cavitation abrasive integrated waterjet peening (CAI-WJP), is proposed in this paper and was studied experimentally. The principle of CAI-WJP is first introduced. The effect of the CAI-WJP parameters (i.e., water pressure, standoff distance, traverse speed, path interval, and peening angle) on the surface integrity of TA19 titanium alloy was systematically investigated. Results show that the specimen treated with CAI-WJP using different process parameters formed a plastic deformation layer with a depth of 5-45 mu m. The minimum surface roughness of Ra obtained by CAI-WJP was 0.348 mu m, which is 28.5% lower than the as-received surface. The maximum surface microhardness increased by up to 21.1%, with a maximum work hardening depth of 150 mu m. The surface compressive residual stress (CRS) increased to approximately 640-800 MPa compared with the original CRS of 50-80 MPa on the as-received specimen, and a maximum CRS depth of 360 mu m was obtained. The microstructure evolution on the topmost surface and subsurface of the specimen treated with CAI-WJP with a water pressure of 100 MPa was observed by transmission electron microscopy, which showed that nanocrystallization with amorphization occurred, and nanocrystals with an average size of 6.9 nm formed on the topmost surface. In addition, many dislocation cells and tangles formed on the subsurface with a depth of 15 mu m, and a number of dislocation loops, walls, and pinning were found at the depth of 150 mu m. This work verifies the effectiveness of the proposed CAI-WJP and provides a favorable reference for how to pick up optimized CAI-WJP process parameters.

关键词： Cavitation abrasive integrated waterjet peening Process parameters Surface integrity microstructure evolutions

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Effect of pre-aging on creep aging properties and microstructure evolution of 2195 Al-Li alloy

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JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T 2022年 21卷 1029-1041页

作者： Chen, Fei Zhong, Jue Zhan, Lihua Wang, Peng Ruan, Xiaopeng Wu, Huiqiang Xu, Yongqian Ma, Bolin Liu, Chunhui Zeng, Quanqing Hu, Zhenggen Zhu, Wenli Cent South Univ Light Alloy Res Inst Changsha 410083 Peoples R China Cent South Univ Sch Mech & Elect Engn Changsha 410083 Peoples R China Cent South Univ State Key Lab High Performance Complex Mfg Changsha 410083 Peoples R China Beijing Inst Aerosp Syst Engn Beijing 100076 Peoples R China

Creep aging forming (CAF) is a potential process to manufacture large integral components of Al-Li alloys, which exhibits poor formability and susceptibility to damage and cracking via traditional plastic forming processes. Al-Li alloys also have disadvantages, such as low creep and comprehensive *** address this problem, this study adopted pre-aging as a treatment process before creep aging (CA). The effects of pre-aging at different temperatures (65 degrees C, 90 degrees C, and 115 degrees C) on the CA of Al-Li alloys were evaluated at 155 degrees C for 18 h. Creep strain, the evolution of mechanical properties, and the microstructural characteristics were investigated as well. The results showed that pre-aging could effectively influence the subsequent CA behavior. As the pre-aging temperature increased, creep strain accumulation during CA decreased. Meanwhile, pre-aging significantly increased the elongation (EL) of the specimens after CA;Notably, the increase in EL did not compromise strength. Changes in the microstructure of the specimens after pre-aging and CA tests were observed by transmission electron mi-croscopy. The effect of pre-aging on the subsequent CA properties mainly revealed that the strength was not lower than that of the specimen without pre-aging after the same CA test through adjusting the percentage and size of the T1 and q' phases. In addition, pre-aging could promote the transformation of the fracture mechanism from intergranular frac-ture to mixed fracture in the specimen after CA.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).

关键词： China Creep aging Mechanical properties microstructure evolutions Al-Li alloy Pre-aging

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