Pub Date : 2024-11-26DOI: 10.1016/j.vacuum.2024.113881
Rongqi Shen , Yi Lu , Zhongxi Zhang
Fused silica is a widely used optical material in high-power solid-state laser systems. The electronic and optical properties of fused silica are affected by point defects and stress in the material. In this paper, the electronic and optical properties of fused silica are calculated using the first-principles method. The study found that the band gap of defect-free fused silica material gradually decreases as the pressure increases. When the fused silica material contains oxygen vacancy or silicon vacancy defects, the band gap size is not proportional to pressure. During the elastic deformation stage, low strain and high strain cause a sudden change in the band gap size of defect-containing fused silica. This paper reveals the mechanism of the influence of pressure on the band gap and optical properties of defect-free and defect-containing fused silica materials from the perspective of micro-stress.
{"title":"Effects of pressure on the electronic and optical properties of defect-free and defect-containing fused silica: A first-principles study","authors":"Rongqi Shen , Yi Lu , Zhongxi Zhang","doi":"10.1016/j.vacuum.2024.113881","DOIUrl":"10.1016/j.vacuum.2024.113881","url":null,"abstract":"<div><div>Fused silica is a widely used optical material in high-power solid-state laser systems. The electronic and optical properties of fused silica are affected by point defects and stress in the material. In this paper, the electronic and optical properties of fused silica are calculated using the first-principles method. The study found that the band gap of defect-free fused silica material gradually decreases as the pressure increases. When the fused silica material contains oxygen vacancy or silicon vacancy defects, the band gap size is not proportional to pressure. During the elastic deformation stage, low strain and high strain cause a sudden change in the band gap size of defect-containing fused silica. This paper reveals the mechanism of the influence of pressure on the band gap and optical properties of defect-free and defect-containing fused silica materials from the perspective of micro-stress.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113881"},"PeriodicalIF":3.8,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722663","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}
Pub Date : 2024-11-24DOI: 10.1016/j.vacuum.2024.113878
Fuyuan Liu , Guantao Wang , Enyu Guo , Zhirou Zhang , Zongning Chen , Huijun Kang , Yanjin Xu , Tongmin Wang
The effects of natural aging (NA) on microstructure and mechanical properties of as-homogenized Al-4.1Cu-1.3Li-0.4Mg-0.4Ag-0.3Mn-0.5Zn-0.1Zr alloy are investigated in this work. The results show that the alloy exhibits a strong NA response attributed to a plethora of GP-Li zones and δ′ precipitated during the initial 3 days which provides nucleation sites for the T1 phase. After 15 days, the mechanical properties dramatically enhance due to the precipitation of the saturated GP-Li zones, δ′, and T1 phases. The yield strength, ultimate tensile strength, and fracture elongation reach 316 MPa, 469 MPa, and 14 % after NA for 15 days, respectively.
{"title":"The precipitation behavior of natural aging for Al-Cu-Li alloy after homogenization","authors":"Fuyuan Liu , Guantao Wang , Enyu Guo , Zhirou Zhang , Zongning Chen , Huijun Kang , Yanjin Xu , Tongmin Wang","doi":"10.1016/j.vacuum.2024.113878","DOIUrl":"10.1016/j.vacuum.2024.113878","url":null,"abstract":"<div><div>The effects of natural aging (NA) on microstructure and mechanical properties of as-homogenized Al-4.1Cu-1.3Li-0.4Mg-0.4Ag-0.3Mn-0.5Zn-0.1Zr alloy are investigated in this work. The results show that the alloy exhibits a strong NA response attributed to a plethora of GP-Li zones and δ′ precipitated during the initial 3 days which provides nucleation sites for the T<sub>1</sub> phase. After 15 days, the mechanical properties dramatically enhance due to the precipitation of the saturated GP-Li zones, δ′, and T<sub>1</sub> phases. The yield strength, ultimate tensile strength, and fracture elongation reach 316 MPa, 469 MPa, and 14 % after NA for 15 days, respectively.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113878"},"PeriodicalIF":3.8,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703662","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}
The transient liquid phase (TLP) bonding process is effective for constructing stacked structures in advanced packaging, as it allows for multiple reflow cycles without remelting. However, the various reflows can cause phase transformations, leading to internal stress-induced voids. Thus, the stability of IMC phases is particularly challenged in 3D stacking structures. Common configurations include Cu/Sn/Cu and Cu/Ni/Sn/Cu. Although Ni improves the stability of the Cu6Sn5 phase, phase transformation to Cu3Sn can still occur, compromising reliability. This study investigates microstructure stability by doping Zn into the Cu/Sn-3.5Ag/Ni system across five reflow cycles. Results demonstrate that Cu-15Zn/Sn-3.5Ag/Ni microbumps reduce void formation and ensuring the phase stability of the (Cu,Ni)6(Sn,Zn)5 to maintain the microstructure stability. The Zn addition inhibits the Cu3Sn layer, while optimizing grain size and orientation of (Cu,Ni)6(Sn,Zn)5. (Cu,Ni)6(Sn,Zn)5 also exhibits increased hardness and reduced modulus (Er). These findings provide critical insights for designing sub-10-μm scale TLP-bonded microbumps in advanced packaging.
{"title":"Microstructural stability enhancement and mechanical reinforcement of TLP-bonded Cu/Sn-3.5Ag/Cu microbumps under multiple reflow cycles through Zn Alloying and Ni substrate integration","authors":"Yin-Ku Lee, Yun-Chen Chan, Zih-Yu Wu, Su-Yueh Tsai, Shou-Yi Chang, Jenq-Gong Duh","doi":"10.1016/j.vacuum.2024.113855","DOIUrl":"10.1016/j.vacuum.2024.113855","url":null,"abstract":"<div><div>The transient liquid phase (TLP) bonding process is effective for constructing stacked structures in advanced packaging, as it allows for multiple reflow cycles without remelting. However, the various reflows can cause phase transformations, leading to internal stress-induced voids. Thus, the stability of IMC phases is particularly challenged in 3D stacking structures. Common configurations include Cu/Sn/Cu and Cu/Ni/Sn/Cu. Although Ni improves the stability of the Cu<sub>6</sub>Sn<sub>5</sub> phase, phase transformation to Cu<sub>3</sub>Sn can still occur, compromising reliability. This study investigates microstructure stability by doping Zn into the Cu/Sn-3.5Ag/Ni system across five reflow cycles. Results demonstrate that Cu-15Zn/Sn-3.5Ag/Ni microbumps reduce void formation and ensuring the phase stability of the (Cu,Ni)<sub>6</sub>(Sn,Zn)<sub>5</sub> to maintain the microstructure stability. The Zn addition inhibits the Cu<sub>3</sub>Sn layer, while optimizing grain size and orientation of (Cu,Ni)<sub>6</sub>(Sn,Zn)<sub>5</sub>. (Cu,Ni)<sub>6</sub>(Sn,Zn)<sub>5</sub> also exhibits increased hardness and reduced modulus (E<sub>r</sub>). These findings provide critical insights for designing sub-10-μm scale TLP-bonded microbumps in advanced packaging.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113855"},"PeriodicalIF":3.8,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722572","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}
Pub Date : 2024-11-23DOI: 10.1016/j.vacuum.2024.113848
Zhiyuan Liu , Rongwei Zha , Zhangjie Tan , Sisheng Liu , Qingjun Hao , Cheng Lei , Du Wang
Nickel (Ni) alloys are widely used in aerospace and nuclear power applications due to their excellent high-temperature performance, corrosion resistance, and fatigue strength. However, the Ni alloy prolonged exposure to extreme conditions, such as high-temperature vapor and alternating cyclic loads, often faced with challenges such as fatigue failure, corrosion and wear. These issues necessitate post-treatment techniques to enhance surface properties, ensuring the reliability and stability of critical structures and components. This study explores the application of laser shock peening (LSP) for refining the microstructure and improving the mechanical properties of Ni alloy (Inconel 690). Experimental results demonstrate LSP effectively improves surface microstructure (∼400 μm), specially forming fine-grained layer (∼150 μm), increases surface hardness by 21.6 % (from 185(±1.32) HV to 225(±7.57) HV), and introduces a compressive residual stress of −319(±50) MPa. Furthermore, a simulation model was developed using finite element method (FEM) and molecular dynamics (MD) to link microstructure and mechanical properties through strain rate, revealing the formation mechanism of fine grain layers and twin crystal. This work provides a theoretical method for the LSP treatment in Ni alloys, and offers simulation framework for investigating the connection between microstructure and mechanical properties in laser surface engineering technologies.
{"title":"Microstructural deformation behavior of laser shock peening Ni alloys: Experimental and molecular dynamics simulation investigations","authors":"Zhiyuan Liu , Rongwei Zha , Zhangjie Tan , Sisheng Liu , Qingjun Hao , Cheng Lei , Du Wang","doi":"10.1016/j.vacuum.2024.113848","DOIUrl":"10.1016/j.vacuum.2024.113848","url":null,"abstract":"<div><div>Nickel (Ni) alloys are widely used in aerospace and nuclear power applications due to their excellent high-temperature performance, corrosion resistance, and fatigue strength. However, the Ni alloy prolonged exposure to extreme conditions, such as high-temperature vapor and alternating cyclic loads, often faced with challenges such as fatigue failure, corrosion and wear. These issues necessitate post-treatment techniques to enhance surface properties, ensuring the reliability and stability of critical structures and components. This study explores the application of laser shock peening (LSP) for refining the microstructure and improving the mechanical properties of Ni alloy (Inconel 690). Experimental results demonstrate LSP effectively improves surface microstructure (∼400 μm), specially forming fine-grained layer (∼150 μm), increases surface hardness by 21.6 % (from 185(±1.32) HV to 225(±7.57) HV), and introduces a compressive residual stress of −319(±50) MPa. Furthermore, a simulation model was developed using finite element method (FEM) and molecular dynamics (MD) to link microstructure and mechanical properties through strain rate, revealing the formation mechanism of fine grain layers and twin crystal. This work provides a theoretical method for the LSP treatment in Ni alloys, and offers simulation framework for investigating the connection between microstructure and mechanical properties in laser surface engineering technologies.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113848"},"PeriodicalIF":3.8,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703163","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}
Pub Date : 2024-11-23DOI: 10.1016/j.vacuum.2024.113859
Bin Li , Yubing Xia , Haonan Li , Mengya Chen , Zhongyuan Wu , Xiaohua Tan , Hui Xu
FeCoNiCuAl high-entropy alloy films (HEAFs) were prepared by direct current magnetron sputtering. The magnetic properties, corrosion resistance in 3.5 wt% NaCl solution and microstructure of the as-deposited and annealed HEAFs were investigated. The results indicated that the as-deposited HEAFs had an amorphous structure. With the increase of annealing temperature, the HEAFs gradually crystallized and the coercivity increased. The as-deposited HEAF had better corrosion resistance than the bulk FeCoNiCuAl high-entropy alloy (HEA), and the Icorr value was 1.41 × 10−6A/cm2. The improved corrosion performance is mainly due to the homogeneity of the composition. After annealing, (Cu, Ni)-rich precipitates appeared in the HEAFs, and the quantity and size of the precipitates increased with increasing annealing temperature. Annealing treatment significantly enhanced the corrosion resistance of the HEAFs. After annealing at 673 K, the optimal Icorr of HEAF was 2.74 × 10−7 A/cm2, which was better than the 304 stainless steel, FeSiB amorphous alloy, some HEAFs, etc. The mechanism of corrosion resistance improvement of the HEAFs after annealing treatment was discussed using scanning electron microscopy and X-ray photoelectron spectroscopy. Good corrosion resistance results from high valence oxides and stable passivation films. This work not only provides direction for the enhancement of corrosion resistance of HEA magnetic films, but also provides candidate materials for magnetic film sensors in harsh environments.
{"title":"The study on the magnetic FeCoNiCuAl high-entropy alloy film with excellent corrosion resistance","authors":"Bin Li , Yubing Xia , Haonan Li , Mengya Chen , Zhongyuan Wu , Xiaohua Tan , Hui Xu","doi":"10.1016/j.vacuum.2024.113859","DOIUrl":"10.1016/j.vacuum.2024.113859","url":null,"abstract":"<div><div>FeCoNiCuAl high-entropy alloy films (HEAFs) were prepared by direct current magnetron sputtering. The magnetic properties, corrosion resistance in 3.5 wt% NaCl solution and microstructure of the as-deposited and annealed HEAFs were investigated. The results indicated that the as-deposited HEAFs had an amorphous structure. With the increase of annealing temperature, the HEAFs gradually crystallized and the coercivity increased. The as-deposited HEAF had better corrosion resistance than the bulk FeCoNiCuAl high-entropy alloy (HEA), and the <em>I</em><sub><em>corr</em></sub> value was 1.41 × 10<sup>−6</sup>A/cm<sup>2</sup>. The improved corrosion performance is mainly due to the homogeneity of the composition. After annealing, (Cu, Ni)-rich precipitates appeared in the HEAFs, and the quantity and size of the precipitates increased with increasing annealing temperature. Annealing treatment significantly enhanced the corrosion resistance of the HEAFs. After annealing at 673 K, the optimal <em>I</em><sub><em>corr</em></sub> of HEAF was 2.74 × 10<sup>−7</sup> A/cm<sup>2</sup>, which was better than the 304 stainless steel, FeSiB amorphous alloy, some HEAFs, etc. The mechanism of corrosion resistance improvement of the HEAFs after annealing treatment was discussed using scanning electron microscopy and X-ray photoelectron spectroscopy. Good corrosion resistance results from high valence oxides and stable passivation films. This work not only provides direction for the enhancement of corrosion resistance of HEA magnetic films, but also provides candidate materials for magnetic film sensors in harsh environments.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113859"},"PeriodicalIF":3.8,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703162","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}
Pub Date : 2024-11-22DOI: 10.1016/j.vacuum.2024.113858
Anat Karlin , Michal Sakajio , Meirav Mann-Lahav , Gennady E. Shter , Shai Zamir , Gideon S. Grader
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.
{"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}
Pub Date : 2024-11-22DOI: 10.1016/j.vacuum.2024.113862
Xin Wen , Xinyu Gao , Shichang Qiao , Fengzhen Wang , Na Li , Shuai Liu , Chao Yuan
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.
{"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}
Pub Date : 2024-11-22DOI: 10.1016/j.vacuum.2024.113837
Sarvjeet Singh , Pankaj K. Arya , Prodyut R. Chakraborty , Hardik B. Kothadia
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.
在实际操作过程中，核反应堆冷却剂系统的完整性和管道内的压力是最值得关注的问题。管道内因断裂/热分层造成的任何泄漏都可能导致高压流体泄漏到低压环境中。这将导致高压下降和从液体到蒸汽的相变，从而造成意外事故。要预测相变的后果并保证核活动的安全，就需要深入了解调节相变的物理学知识。目前的工作旨在通过实验观察加深对低压汽化的理解。为了研究低压汽化，我们建立了一个新的实验装置。实验的初始温度从 65 °C 到 80 °C，初始水高从 100 mm 到 140 mm，高真空罐压力从 11.32 kPa 到 31.32 kPa。根据压力差，该过程分为两个不同的区域和各自的阶段。工作中描述了静态过热和瞬时过热的概念。结果表明，第一区的温降远小于闪蒸区。闪蒸时间可以通过增加水池高度和初始温度来延长。瞬时过热度与初始温度有直接关系，但与水池的初始高度成反比。这些结果将有利于改进核冷却剂系统的设计和解决安全问题。
{"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}
Pub Date : 2024-11-22DOI: 10.1016/j.vacuum.2024.113863
Ping Zhang , Yeran Gao , Yan Yu , Yajie Sun , Hanping Zhou , Jinlong Zhang
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.
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