IF 3.8 2区材料科学

Vacuum Pub Date : 2024-11-22 DOI: 10.1016/j.vacuum.2024.113860

Soheil Shaker, Samuel Afolabi, Olanrewaju Ojo

引用次数: 0

Dielectric high gradient insulator – Progress towards multilayer insulating structures 高梯度介质绝缘体 - 多层绝缘结构的进展

IF 3.8 2区材料科学

Vacuum Pub Date : 2024-11-22 DOI: 10.1016/j.vacuum.2024.113858

Anat Karlin , Michal Sakajio , Meirav Mann-Lahav , Gennady E. Shter , Shai Zamir , Gideon S. Grader

{"title":"Dielectric high gradient insulator – Progress towards multilayer insulating structures","authors":"Anat Karlin , Michal Sakajio , Meirav Mann-Lahav , Gennady E. Shter , Shai Zamir , Gideon S. Grader","doi":"10.1016/j.vacuum.2024.113858","DOIUrl":"10.1016/j.vacuum.2024.113858","url":null,"abstract":"<div><div>High gradient insulators (HGI) consisting of ceramic and metallic alternating layer structure, have been shown to reduce surface breakdown occurrence in high voltage devices. Recently, the HGI's metal layers were replaced with high dielectric constant ceramics, creating dielectric high gradient insulators (DHGI) that were shown to outperform pure alumina analog. A 2-layer DHGI prototype manufactured by spark plasma sintering (SPS) demonstrated an increased surface breakdown field and fewer surface breakdowns during conditioning, compared to plain alumina. However, weak breakdowns at the opposite polarity were observed in the 2-layer structure. This study focuses on overcoming this issue by introducing a 3-layer design, with two high dielectric layers capping a plain alumina layer. Breakdown tests confirmed the elimination of weak breakdowns and improved dielectric strength, consistent with simulations predictions. Additionally, post-SPS air annealing was shown to be essential for removing adsorbed gases and recovering the high dielectric layers composition that changed during SPS. The annealed DHGIs were shown to reduce significantly the breakdown pulses during high-voltage conditioning. The 3-layer DHGI exhibited a 33.5 % higher breakdown field than plain alumina and a 13.5 % improvement over the 2-layer DHGI reported earlier.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113858"},"PeriodicalIF":3.8,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A new understanding of phase transformation in vacuum electron beam welding of NS163 Co-based superalloy and AISI 410L stainless steel: Based on in situ observation and variant selection 对 NS163 Co 基超合金和 AISI 410L 不锈钢真空电子束焊接中相变的新认识：基于现场观察和变体选择

IF 3.8 2区材料科学

Vacuum Pub Date : 2024-11-22 DOI: 10.1016/j.vacuum.2024.113862

Xin Wen , Xinyu Gao , Shichang Qiao , Fengzhen Wang , Na Li , Shuai Liu , Chao Yuan

{"title":"A new understanding of phase transformation in vacuum electron beam welding of NS163 Co-based superalloy and AISI 410L stainless steel: Based on in situ observation and variant selection","authors":"Xin Wen , Xinyu Gao , Shichang Qiao , Fengzhen Wang , Na Li , Shuai Liu , Chao Yuan","doi":"10.1016/j.vacuum.2024.113862","DOIUrl":"10.1016/j.vacuum.2024.113862","url":null,"abstract":"<div><div>This study establishes a link between crystallographic variants and mechanical properties at both the edge and center regions of NS163 Co-based superalloy wires and AISI 410L stainless steel plates welded joints. The thermal cycle of vacuum electron beam welding was simulated using in situ laser confocal microscopy to clarify the martensitic transformation process. Results indicate that martensite preferentially nucleates at grain boundaries, maintaining the Kurdjumov-Sachs orientation relationship with the parent austenite. Most variant boundaries in these regions correspond to variants within the same crystal packet, with V1/V3&V5 emerging as dominant pairs. At the edge, the increased cooling rate and temperature gradient amplify the driving force for martensitic transformation, fostering the generation of diverse variants. Conversely, lower cooling rate at the center raises the martensitic transformation temperature and expands variant selection. The study notes significant dislocation slip during micropillar compression, with the edge of weld exhibiting finer martensite laths and dense dislocations, which enhances strength (∼1279 MPa) compared to the center (∼1040 MPa), aligning with the results obtained via nanoindentation. The observed \"size effect\" results in a twice strength as measured by micropillar compression compared to nanoindentation. Additionally, staggered Bain groups at the edge include a greater number of high angle grain boundaries, indirectly improving toughness. This research aligns with recent literature and aids in the development of compositional design and machining techniques for heterogeneous welds.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113862"},"PeriodicalIF":3.8,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Insight into the evaporation characteristics of vacuum environment describing the different zones 深入了解描述不同区域的真空环境蒸发特性

IF 3.8 2区材料科学

Vacuum Pub Date : 2024-11-22 DOI: 10.1016/j.vacuum.2024.113837

Sarvjeet Singh , Pankaj K. Arya , Prodyut R. Chakraborty , Hardik B. Kothadia

{"title":"Insight into the evaporation characteristics of vacuum environment describing the different zones","authors":"Sarvjeet Singh , Pankaj K. Arya , Prodyut R. Chakraborty , Hardik B. Kothadia","doi":"10.1016/j.vacuum.2024.113837","DOIUrl":"10.1016/j.vacuum.2024.113837","url":null,"abstract":"<div><div>The integrity of the nuclear reactor coolant system and the pressure within the pipes are of utmost concern during the practical operation. Any leakage in the pipes due to fracture/thermal stratification can cause the leakage of high-pressure fluid into the low-pressure environment. This results in a high-pressure drop and phase change from liquid to vapour, which causes accidental mishaps. In depth knowledge of the physics that regulates phase change is needed to forecast the consequences of phase change and guarantee the safety of nuclear activities. The present work aims to augment the understanding of low pressure vaporization through experimental observations. A new experimental setup has been set up to study low pressure vaporization. Experiments are conducted with different initial temperatures ranging from 65 °C to 80 °C, initial water heights between 100 mm to 140 mm, and high vacuum tank pressure varying from 11.32 to 31.32 kPa. Based on the pressure difference, The process is characterized into two different zones and their respective stages. The concept of static superheat and instant superheat is described in the work. The results show that the temperature drop during the first zone is much less than the flashing zone. Flashing time can be increased by increasing the pool height and initial temperature. Instant superheat has a direct relationship to the initial temperature but has an inverse relation to the initial height of the pool. These outcomes will be advantageous in enhancing the design of nuclear coolant systems and addressing safety concerns.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113837"},"PeriodicalIF":3.8,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effects of water-guided laser surface strengthening on surface properties and fatigue life of TC4 titanium alloy in tension-tension fatigue tests 水引导激光表面强化对 TC4 钛合金拉伸疲劳试验中表面性能和疲劳寿命的影响

IF 3.8 2区材料科学

Vacuum Pub Date : 2024-11-22 DOI: 10.1016/j.vacuum.2024.113863

Ping Zhang , Yeran Gao , Yan Yu , Yajie Sun , Hanping Zhou , Jinlong Zhang

{"title":"Effects of water-guided laser surface strengthening on surface properties and fatigue life of TC4 titanium alloy in tension-tension fatigue tests","authors":"Ping Zhang , Yeran Gao , Yan Yu , Yajie Sun , Hanping Zhou , Jinlong Zhang","doi":"10.1016/j.vacuum.2024.113863","DOIUrl":"10.1016/j.vacuum.2024.113863","url":null,"abstract":"<div><div>In this study, we introduce a novel surface strengthening technique known as Water-Jet Guided Laser (WJGL) strengthening. This method is investigated for its impact on the surface properties of TC4 titanium alloy, highlighting its effectiveness in enhancing material performance and extending service life. WJGL strengthening influences material characteristics by adjusting jet velocity and laser overlap ratio.Surface roughness increases with higher jet velocities, and residual stress distribution is similarly affected. Specifically, at a 30 % overlap ratio, surface roughness values rise by 0.0562, 0.2551, and 0.6634 μm as jet velocity increases from 300 to 400 mm/s. Residual compressive stress initially increases with jet velocity, reaching peaks of 827.5, 1018.8, and 1003.3 MPa, before declining.The technique shows consistent effects on maximum residual compressive stress across various overlap ratios, with jet velocity being the primary factor affecting residual stress distribution. WJGL strengthening significantly improves high-cycle fatigue life and thermo-mechanical fatigue performance under tensile-tensile loading conditions. Higher jet velocities correlate with an increased number of cycles to failure in high-cycle fatigue testing. The fracture-prone area initially contracts and then expands, likely due to changes in residual stress.In thermo-mechanical fatigue tests, the central region exhibits a reduced lifespan, indicating a concentrated stress distribution. Fatigue cycle counts show a consistent pattern across different overlap ratios and jet velocities, with higher overlap ratios contributing to longer fatigue life.Compared to traditional techniques such as Water-Jet (WJ) and Laser Shock Peening (LSP), WJGL strengthening demonstrates superior performance and presents a promising approach for material enhancement.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113863"},"PeriodicalIF":3.8,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Study on surface integrity and crack propagation mechanism of Ti/Al composite plates enhanced based on water jet peening 基于喷水强化的钛铝复合板表面完整性和裂纹扩展机理研究

IF 3.8 2区材料科学

Vacuum Pub Date : 2024-11-21 DOI: 10.1016/j.vacuum.2024.113818

Ping Zhang , Yeran Gao , Xiaomin Jiang , Yan Yu , Youqiang Wang

{"title":"Study on surface integrity and crack propagation mechanism of Ti/Al composite plates enhanced based on water jet peening","authors":"Ping Zhang , Yeran Gao , Xiaomin Jiang , Yan Yu , Youqiang Wang","doi":"10.1016/j.vacuum.2024.113818","DOIUrl":"10.1016/j.vacuum.2024.113818","url":null,"abstract":"<div><div>This study investigates the mechanisms through which water jet (WJ) enhancement affects surface integrity and crack propagation in Ti/Al composite plates. Finite element models for both WJ enhancement and crack propagation were developed using ABAQUS, complemented by experiments analyzing the influence of different jet velocities on surface integrity parameters, such as residual stress and surface roughness. These parameters were then examined for their effects on the stress intensity factor (SIF), fatigue crack propagation rate (FCP), and crack propagation path.The results demonstrated a positive relationship between jet velocity and both surface roughness and maximum residual compressive stress in specimens treated with WJ enhancement. Specifically, as jet velocity increased from 300 mm/s to 350 mm/s, surface roughness rose approximately 4.2-fold to around 0.95813 μm, while maximum residual compressive stress increased from 1109.9 MPa to 1472.5 MPa. The uniform distribution of residual compressive stress contributed significantly to the reduction in the stress intensity factor.Additionally, the crack propagation rate was inversely correlated with jet velocity. The residual compressive stress induced by higher jet velocities effectively slowed crack propagation. The theoretical interpretation of residual compressive stress as an equivalent damping layer further validated the effectiveness of WJ enhancement in reducing crack propagation in Ti/Al composites.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113818"},"PeriodicalIF":3.8,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Phase evolution and mechanical properties of AlxCrTaTi refractory medium entropy alloys AlxCrTaTi 难熔中熵合金的相变和机械性能

IF 3.8 2区材料科学

Vacuum Pub Date : 2024-11-20 DOI: 10.1016/j.vacuum.2024.113847

Xiangxing Xiao , Jiadong Wen , Kechuan Wei , Xian Wang , Xingdong Zhao , Xingqiang Wang , Guixue Zhang , Ying Xu , Yan Wei , Hualong Ge , Hongzhong Cai , Xuehang Wang , Li Chen , Junmei Guo , Kunhua Zhang , Changyi Hu

{"title":"Phase evolution and mechanical properties of AlxCrTaTi refractory medium entropy alloys","authors":"Xiangxing Xiao , Jiadong Wen , Kechuan Wei , Xian Wang , Xingdong Zhao , Xingqiang Wang , Guixue Zhang , Ying Xu , Yan Wei , Hualong Ge , Hongzhong Cai , Xuehang Wang , Li Chen , Junmei Guo , Kunhua Zhang , Changyi Hu","doi":"10.1016/j.vacuum.2024.113847","DOIUrl":"10.1016/j.vacuum.2024.113847","url":null,"abstract":"<div><div>In multi-principal refractory alloys (high-entropy alloys, medium-entropy alloys), the presence of the second phase has an important influence on the mechanical properties of the alloys. In this paper, AlxCrTaTi (x = 0, 0.25, 0.5, 1.0) refractory medium-entropy alloys were prepared by vacuum arc melting method, and the microstructure, density, and mechanical properties were investigated. The CrTaTi alloy consists of BCC dendritic and C15 Laves phases, whereas the Al<sub>x</sub>CrTaTi alloys consist of a two-phase eutectic organization (BCC phase and C14 Laves phase). With the increase of Al content, the content of the second phase increases from 15.97 % to 42.19 %, resulting in an increase in the yield strength of the alloy from 1491 MPa to 2354 MPa at 25 °C, and from 253 MPa to 426 MPa at 1000 °C. The addition of Al element changes the enthalpy, elemental distribution, and solidification process of the alloy, resulting in the formation of Cr-rich and Ti-rich two-phase eutectic organizations in the alloy. With the increase of Al, the second phase strengthening is the main reason for the enhancement of alloy properties.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113847"},"PeriodicalIF":3.8,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Synthesis and characterization of ammonia strengthened and ambient dried N-doped hydrophilic graphene aerogel with good electrical conductivity 具有良好导电性的氨强化和常温干燥 N 掺杂亲水石墨烯气凝胶的合成与表征

IF 3.8 2区材料科学

Vacuum Pub Date : 2024-11-20 DOI: 10.1016/j.vacuum.2024.113846

Feng Xiong , Jiabin Wang , Neville Dickman , Yujing Liu , Michael R.C. Hunt , Lidija Šiller

引用次数: 0

Influence of oxygen on metastable pitting behavior of super 13Cr stainless steel in CO2-saturated environment 氧气对二氧化碳饱和环境中超 13Cr 不锈钢瞬态点蚀行为的影响

IF 3.8 2区材料科学

Vacuum Pub Date : 2024-11-19 DOI: 10.1016/j.vacuum.2024.113845

Lv Naixin , Fu Anqing , Chen Chao , Bai Haitao , Zhao Zaipeng , Li Xuanpeng , Xu Zhengyi , Guozhe Meng

引用次数: 0

Modelling and working process mechanism of a double-claw vacuum pump with novel double-claw rotors 带有新型双爪转子的双爪真空泵的建模和工作过程机理

IF 3.8 2区材料科学

Vacuum Pub Date : 2024-11-19 DOI: 10.1016/j.vacuum.2024.113844

Min Wei, Haibin Liu, Lezhi Ye, Yanfeng Wei, Yue Chang

{"title":"Modelling and working process mechanism of a double-claw vacuum pump with novel double-claw rotors","authors":"Min Wei, Haibin Liu, Lezhi Ye, Yanfeng Wei, Yue Chang","doi":"10.1016/j.vacuum.2024.113844","DOIUrl":"10.1016/j.vacuum.2024.113844","url":null,"abstract":"<div><div>Double-claw rotors can significantly increase the pumping speed of the claw vacuum pump. In order to develop new claw rotors with higher comprehensive performance, in this study, a novel type of two intermeshing double-claw rotors consisting of the elliptical arc, line segment, circular arc and their conjugate curves was proposed. A geometric model of the proposed double-claw rotor was established, and profile equations were also derived. The effects of its independent geometric parameters of the proposed double-claw rotors on the performance were analyzed, and then a corresponding double-claw vacuum pump with these novel rotors was designed. Meanwhile, its the working process was studied and numerically simulated. Results indicate that the proposed double-claw rotor offers several significant advantages, including a higher pumping speed, improved profile meshing characteristics, and enhanced dynamic balance performance. The working process of the double-claw vacuum pump includes 5 processes: suction process, isometric delivery process, compression process, discharge process and mixing process. The contents of this study will provide theoretical basis for the development of the double-claw vacuum pump and promote its application.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113844"},"PeriodicalIF":3.8,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Vacuum最新文献