Crystals

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14 pages, 6664 KiB

Open AccessArticle

Joining 3YSZ Electrolyte to AISI 441 Interconnect Using the Ag Particle Interlayer: Enhanced Mechanical and Aging Properties

by Xiaoqing Si, Xiaoyang Wang, Chun Li, Tong Lin, Junlei Qi and Jian Cao

Crystals 2021, 11(12), 1573; https://doi.org/10.3390/cryst11121573 - 16 Dec 2021

Cited by 7 | Viewed by 2603

Abstract

Reactive air brazing has been widely used in fabricating solid oxide fuel/electrolysis cell (SOFC/SOEC) stacks. However, the conventional Ag–CuO braze can lead to (I) over oxidation at the steel interconnect interface caused by its adverse reactions with the CuO and (II) many voids [...] Read more.

Reactive air brazing has been widely used in fabricating solid oxide fuel/electrolysis cell (SOFC/SOEC) stacks. However, the conventional Ag–CuO braze can lead to (I) over oxidation at the steel interconnect interface caused by its adverse reactions with the CuO and (II) many voids caused by the hydrogen-induced decomposition of CuO. The present work demonstrates that the Ag particle interlayer can be used to join yttria-stabilized zirconia (YSZ) electrolytes to AISI 441 interconnect in air instead of Ag–CuO braze. Reliable joining between YSZ and AISI 441 can be realized at 920 °C. A dense and thin oxide layer (~2 μm) is formed at the AISI 441 interface. Additionally, an interatomic joining at the YSZ/Ag interface was observed by TEM. Obtained joints displayed a shear strength of ~86.1 MPa, 161% higher than that of the joints brazed by Ag–CuO braze (~33 MPa). After aging in reducing and oxidizing atmospheres (800 °C/300 h), joints remained tight and dense, indicating a better aging performance. This technique eliminates the CuO-induced issues, which may extend lifetimes for SOFC/SOEC stacks and other ceramic/metal joining applications. Full article

(This article belongs to the Special Issue Preparation, Microstructure Evolution and Mechanical Study of the Brazed Joints)

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7 pages, 2086 KiB

Open AccessArticle

Microstructure of Ag Nano Paste Joint and Its Influence on Reliability

by Dongsheng Yang, Yilong Huang and Yanhong Tian

Crystals 2021, 11(12), 1537; https://doi.org/10.3390/cryst11121537 - 9 Dec 2021

Cited by 9 | Viewed by 2478

Abstract

In this paper, the microstructure of Ag nano paste joint was investigated in pressure-less sintering conditions, and the influence of the microstructure on the joint’s reliability was studied. Firstly, silver nanoparticles (Ag NPs) were synthesized using the redox reaction method. To tightly stack [...] Read more.

In this paper, the microstructure of Ag nano paste joint was investigated in pressure-less sintering conditions, and the influence of the microstructure on the joint’s reliability was studied. Firstly, silver nanoparticles (Ag NPs) were synthesized using the redox reaction method. To tightly stack the Ag NPs in nano paste, Ag NPs with sizes of 30~50 nm and submicron-sized Ag particles were mixed. It was found that increasing the sintering temperature or sintering time can reduce the porosity of the bonding layer and the interfacial crack simultaneously, resulting in higher shear strength. When sintering at a temperature of 250 °C, a complete bonding interface was formed, with a 0.68 μm interdiffusion layer. At a higher temperature (300 °C), the bonding interface reached 1.5 μm, providing 35.9 ± 1.7 MPa of shear strength. The reliability of the die attachment was analyzed under thermal shocking from −65 °C to 150 °C for 50 cycles. As the crack could quickly grow through the interfacial defects, the separation ratio was 85% and 67% when sintered at 150 °C and 200 °C, respectively. Because of the reliable bonding interface between the die and the substrate, the Ag nano paste joint formed a slight crack on the edge of the die when sintering at 250 °C. When the joint was sintered at 300 °C, the small voids became large voids, which featured lower resistance to crack growth. Thus, instead of further improved reliability, the separation ratio increased to 37%. Full article

(This article belongs to the Special Issue Preparation, Microstructure Evolution and Mechanical Study of the Brazed Joints)

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11 pages, 3675 KiB

Open AccessArticle

Reactive Air Brazing of TiAl Alloy Using Ag-CuO: Microstructure and Joint Properties

by Haoran Yang, Xiaoqing Si, Chun Li and Jian Cao

Crystals 2021, 11(12), 1496; https://doi.org/10.3390/cryst11121496 - 2 Dec 2021

Cited by 2 | Viewed by 1959

Abstract

TiAl alloy was successfully brazed with Ag-CuO filler in air atmosphere under simple technical conditions. The wettability of a series of Ag-CuO fillers on TiAl was analyzed. Ag-2mol%CuO filler possessed good wetting behavior on TiAl alloy. The microstructure and mechanical properties of the [...] Read more.

TiAl alloy was successfully brazed with Ag-CuO filler in air atmosphere under simple technical conditions. The wettability of a series of Ag-CuO fillers on TiAl was analyzed. Ag-2mol%CuO filler possessed good wetting behavior on TiAl alloy. The microstructure and mechanical properties of the brazed joints were investigated. Oxide layers can be found on both sides, which can be divided into external TiO₂-rich layer and internal Al₂O₃-rich layer. The maximum shear strength of the joint was obtained at 1020 °C holding for 20 min. Full article

(This article belongs to the Special Issue Preparation, Microstructure Evolution and Mechanical Study of the Brazed Joints)

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11 pages, 3341 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Vacuum Diffusion Bonded Zr-4 Alloy Joint

by Zeming Wang, Xu Yang, Jing Wang, Zhonglin Xiao, Fugong Qi, Kongbo Sun, Ying Wang and Zhenwen Yang

Crystals 2021, 11(11), 1437; https://doi.org/10.3390/cryst11111437 - 22 Nov 2021

Cited by 9 | Viewed by 2615

Abstract

The development of welding technology for zirconium alloy has great significance on the safety, stability, and reliability of the operation of the nuclear reactor. In this work, vacuum diffusion bonding of Zr-4 alloy was studied at the diffusion temperature ranging from 760 to [...] Read more.

The development of welding technology for zirconium alloy has great significance on the safety, stability, and reliability of the operation of the nuclear reactor. In this work, vacuum diffusion bonding of Zr-4 alloy was studied at the diffusion temperature ranging from 760 to 820 °C with holding times of 30–90 min. The effects of diffusion bonding temperature and holding time on the interfacial microstructure and mechanical properties of the diffusion bonded Zr-4 alloy joints were investigated in detail, and the relationship between the interfacial microstructure and shear strength of the diffusion bonded joints was discussed. The results show that the interface bonding ratio of the diffusion bonded Zr-4 joint gradually increased from 74% to 95% with the increasing of bonding temperature. In addition, the grain size of the base material became a larger and brittle second phase composed of Zr(Cr, Fe)₂ and eutectic α-Zr + Zr(Fe, Cr)₂ formed in the joint with the increase of the temperature as well as the extension of the bonding time. The highest shear strength of 349 MPa was obtained at 800 °C for 30 min under 7 MPa, and the crack of the joint was primarily propagated along with the base material rather than the bonded interface. Full article

(This article belongs to the Special Issue Preparation, Microstructure Evolution and Mechanical Study of the Brazed Joints)

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5 pages, 2904 KiB

Open AccessCommunication

Crystallization Behavior in Bi₂O₃-B₂O₃-ZnO Glass Braze and Its Application for Joining Ferrite Ceramics at a Relatively Low Temperature

by Wei Guo, Li Fu and Peng He

Crystals 2021, 11(8), 1007; https://doi.org/10.3390/cryst11081007 - 23 Aug 2021

Cited by 3 | Viewed by 2099

Abstract

50Bi₂O₃-30B₂O₃-20ZnO (mol.%) glass was designed and prepared in our previous work. On the basis of preliminary work on DSC analysis, the crystallization behavior of the glass was further investigated in the present work. The results [...] Read more.

50Bi₂O₃-30B₂O₃-20ZnO (mol.%) glass was designed and prepared in our previous work. On the basis of preliminary work on DSC analysis, the crystallization behavior of the glass was further investigated in the present work. The results showed that Bi₃₈ZnO₅₈ and Bi₄₅BO₆₉ crystals were formed in the glass during the heating process. Subsequently, ferrite ceramics were then brazed at one of the peak temperatures, 551 °C. The results showed that Bi₃₈ZnO₅₈ and Bi₄₅BO₆₉ crystals were formed in the joint domain, and the joint possessed a shear strength value of 76.6 MPa. Full article

(This article belongs to the Special Issue Preparation, Microstructure Evolution and Mechanical Study of the Brazed Joints)

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11 pages, 3941 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Vacuum Diffusion Bonded Ti₂AlNb/Ti/TC4 Joint

by Yifeng Wang, Bingxu Hu, Yan Wei, Guangjie Feng and Dean Deng

Crystals 2021, 11(7), 770; https://doi.org/10.3390/cryst11070770 - 1 Jul 2021

Cited by 7 | Viewed by 2468

Abstract

In this paper, the Ti₂AlNb alloy was bonded to TC4 alloy using the vacuum diffusion bonding method with a Ti interlayer. The interfacial microstructure of the Ti₂AlNb/Ti/TC4 joint was characterized. The relationship between the bonding parameters and the microstructure [...] Read more.

In this paper, the Ti₂AlNb alloy was bonded to TC4 alloy using the vacuum diffusion bonding method with a Ti interlayer. The interfacial microstructure of the Ti₂AlNb/Ti/TC4 joint was characterized. The relationship between the bonding parameters and the microstructure and mechanical property of the joints was explored. Results indicated that the interdiffusion of Nb and Al elements between the interlayer and substrates promoted the formation of the lamellar α + β dual-phase structure in the joint. The bonding parameters determined the diffusion distance of Nb and Al elements, thus controlling the characteristics of the lamellar α + β dual-phase structure. When the Ti₂AlNb alloy and TC4 alloy were bonded at 950 °C for 30 min under a pressure of 10 MPa, the elemental diffusion in the bonding couple was sufficient and the joint possessed the maximum shear strength of 549 MPa. Full article

(This article belongs to the Special Issue Preparation, Microstructure Evolution and Mechanical Study of the Brazed Joints)

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12 pages, 2473 KiB

Open AccessArticle

Interface Behavior of Brazing between Zr-Cu Filler Metal and SiC Ceramic

by Bofang Zhou, Taohua Li, Hongxia Zhang and Junliang Hou

Crystals 2021, 11(7), 727; https://doi.org/10.3390/cryst11070727 - 23 Jun 2021

Cited by 3 | Viewed by 1982

Abstract

The interface behavior of brazing between Zr-Cu filler metal and SiC ceramic was investigated. Based on the brazing experiment, the formation of brazing interface products was analyzed using OM, SEM, XRD and other methods. The stable chemical potential phase diagram was established to [...] Read more.

The interface behavior of brazing between Zr-Cu filler metal and SiC ceramic was investigated. Based on the brazing experiment, the formation of brazing interface products was analyzed using OM, SEM, XRD and other methods. The stable chemical potential phase diagram was established to analyze the possible diffusion path of interface elements, and then the growth behavior of the interface reaction layer was studied by establishing relevant models. The results show that the interface reaction between the active element Zr and SiC ceramic is the main reason in the brazing process the interface products are mainly ZrC and Zr₂Si and the possible diffusion path of elements in the product formation process is explained. The kinetic equation of interfacial reaction layer growth is established, and the diffusion constant (2.1479 μm·s^1/2) and activation energy (42.65 kJ·mol⁻¹) are obtained. The growth kinetics equation of interfacial reaction layer thickness with holding time at different brazing temperatures is obtained. Full article

(This article belongs to the Special Issue Preparation, Microstructure Evolution and Mechanical Study of the Brazed Joints)

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14 pages, 7580 KiB

Open AccessArticle

Wetting Behavior of the Ag-5CuO Brazing Alloy on ZTA Composite Ceramic with/without CuO Coating in Air

by Guangjie Feng, Manqin Liu, Yalei Liu, Zhouxin Jin, Yifeng Wang and Dean Deng

Crystals 2021, 11(6), 609; https://doi.org/10.3390/cryst11060609 - 28 May 2021

Cited by 2 | Viewed by 2252

Abstract

The wetting of Ag-5 wt.% CuO (Ag-5CuO) alloy on initial/CuO-coated zirconia toughened alumina (ZTA) composite ceramic in air was studied in detail. The results showed that the contact angle of the Ag-5CuO/ZTA system rapidly decreased from 81° at 970 °C to 45° at [...] Read more.

The wetting of Ag-5 wt.% CuO (Ag-5CuO) alloy on initial/CuO-coated zirconia toughened alumina (ZTA) composite ceramic in air was studied in detail. The results showed that the contact angle of the Ag-5CuO/ZTA system rapidly decreased from 81° at 970 °C to 45° at 990 °C during the heating process, however, moderate reductions in contact angle were observed in the subsequent heating and temperature holding stages. In comparison with the contact angle of pure Al₂O₃, an increment of about 4° of the stable contact angle of Ag-5CuO alloy on the heterogeneous ZTA was observed. The reaction between Al₂O₃ and CuO can reduce the damage of the CuO-rich liquid to ZrO₂ in the ZTA substrate. Both oxygen and CuO were helpful in reducing the contact angle of Ag on ZTA and enhancing the bonding of the Ag/ZTA interface. The continuous CuO coating on ZTA and the monotectic liquid containing more CuO in the region near the triple line induced reductions of more than 40° and about 10° in the contact angle, respectively, between the initial and the CuO coating-improved wetting systems. Full article

(This article belongs to the Special Issue Preparation, Microstructure Evolution and Mechanical Study of the Brazed Joints)

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14 pages, 4293 KiB

Open AccessArticle

Bonding SiCp/Al Composites via Laser-Induced Exothermic Reactions

by Yifeng Wang, Guangjie Feng, Yan Wei, Bingxu Hu and Dean Deng

Crystals 2021, 11(5), 535; https://doi.org/10.3390/cryst11050535 - 12 May 2021

Cited by 3 | Viewed by 1810

Abstract

In this paper, the SiCp/Al composites were bonded via laser-induced exothermic reactions of a Ni–Al–Zr interlayer. The Ni–Al–Zr interlayer was designed based on its exothermic property and chemical compatibility with the SiCp/Al composites. The influences of the interlayer composition and bonding pressure on [...] Read more.

In this paper, the SiCp/Al composites were bonded via laser-induced exothermic reactions of a Ni–Al–Zr interlayer. The Ni–Al–Zr interlayer was designed based on its exothermic property and chemical compatibility with the SiCp/Al composites. The influences of the interlayer composition and bonding pressure on the joint microstructure and shear strength were investigated. Results indicated that high exothermic reactions occurred in the Ni–Al–Zr interlayer and realized the reliable bonding with the SiCp/Al composites. The interlayer products were the eutectic structure of NiAl+Ni₂AlZr+Ni₃Al₅Zr₂. NiAl₃ and Ni₂Al₃ reaction layers were formed at the bonding interfaces. The interlayer composition and the bonding pressure determined the morphology and distribution of the voids and the reaction layers, thus controlling the joint shear strength. When the SiCp/Al composites were bonded using the interlayer with the Zr content of 15 wt.% under the bonding pressure of 3 MPa, the joint shear strength reached the maximum of 24 MPa. Full article

(This article belongs to the Special Issue Preparation, Microstructure Evolution and Mechanical Study of the Brazed Joints)

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15 pages, 7330 KiB

Open AccessArticle

Experimental and Numerical Study of Transient Liquid Phase Diffusion Bonded DZ40M Superalloys

by Zhan Sun, Xi Chen, Lixia Zhang, Saisai Zhang and Jicai Feng

Crystals 2021, 11(5), 479; https://doi.org/10.3390/cryst11050479 - 25 Apr 2021

Cited by 4 | Viewed by 2395

Abstract

Transient liquid phase (TLP) diffusion bonding of DZ40M cobalt-based superalloy was carried out using a self-made NiCrCoWB intermediate layer. The typical microstructure of the joint was investigated. The effect of holding time on the microstructural evolution and the tensile strength of the brazed [...] Read more.

Transient liquid phase (TLP) diffusion bonding of DZ40M cobalt-based superalloy was carried out using a self-made NiCrCoWB intermediate layer. The typical microstructure of the joint was investigated. The effect of holding time on the microstructural evolution and the tensile strength of the brazed joints was studied. The tensile strength of the joints TLP bonded at 1160 °C for 60 min reached the maximum value of 487 MPa, which was 88.6% of the base metal strength. The diffusion of boron and the evolution of the eutectic zone were numerically studied. The time needed for isothermal solidification completion was calculated and predicted, which was well in accordance with the experimental results. Full article

(This article belongs to the Special Issue Preparation, Microstructure Evolution and Mechanical Study of the Brazed Joints)

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