Thermochemistry of brazing ceramics and metals in air

Bobzin, Kirsten; Schläfer, Thomas; Kopp, Nils

doi:10.3139/146.110550

Cited by 19 publications

(12 citation statements)

References 7 publications

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“…AgCu-based filler metals on AISI 314 have been investigated in previous studies. [24] These studies confirm the known behavior of the Ag-CuO system in air which starts to melt at around 937°C. During DSC measurement of the Ag-CuO system on an inert substrate, a second endothermic peak occurs due to the formation of a second, Cu-rich melt.…”

Section: Thermochemical Behaviorsupporting

confidence: 76%

Characterization of Reactive Air Brazed Ceramic/Metal Joints with Unadapted Thermal Expansion Behavior

et al. 2014

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Reactive air brazing (RAB) is a promising and economic method for joining ceramic to metal as well as ceramic to ceramic. Hybrid joints gain importance in the field of challenging applications such as gas separation or solid oxide fuel cells. While the ceramic partner is often directly chosen due to its functionality, the metallic partner needs to be chosen carefully in order to avoid high residual stresses due to the differences in the thermal expansion coefficients. This leads to the restriction of the usage of a significant number of potential joining partners. Ceramic/metals components with unadapted thermal expansion behavior (Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-d /Crofer 22 H and 3YSZ/AISI 314) were joined by RAB. Cu-containing as well as Cu-free Ag-based filler metals were used. Analysis of the cross-section of brazed samples showed that the microstructure of the samples depends especially on the used filler metal. The melting process as well as the exothermic reactions leading to a distinct reaction zone could be observed in the differential scanning calorimetric measurements. While the microstructure of the joints is not significantly influenced by the base material, the strength of the BSCF/Crofer 22 H specimens is nearly four times lower than the strength of the specimens with the adapted thermal expansion coefficients (BSCF/AISI 314 and 3YSZ/Crofer 22 H). The reasons are residual stresses caused by the different thermal expansion coefficients. Finite element simulations assuming a viscoplastic material model show that an amount of stress can be reduced by relaxation within the silver based braze. But the volume of the high residual stresses is still larger in the BSCF/Crofer 22 H joints than that of the BSCF/AISI 314 joint resulting in a lower fracture strength.

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Section: Thermochemical Behaviorsupporting

confidence: 76%

Characterization of Reactive Air Brazed Ceramic/Metal Joints with Unadapted Thermal Expansion Behavior

et al. 2014

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“…[20] The DSC curve of Ag8Cu(O) on Al 2 O 3 ( Figure 6) comprises two endothermal peaks, which represent the liquidus reaction Ag þ CuO ! [20] The DSC curve of Ag8Cu(O) on Al 2 O 3 ( Figure 6) comprises two endothermal peaks, which represent the liquidus reaction Ag þ CuO !…”

Section: Dsc Analysismentioning

confidence: 99%

“…For a better understanding of the melting and solidification processes, the behavior of the brazes on differing joining partners were thermally analyzed by DSC measurement. [20] The DSC curve of Ag8Cu(O) on Al 2 O 3 ( Figure 6) comprises two endothermal peaks, which represent the liquidus reaction Ag þ CuO ! L 2 þ CuO and the solidus reaction L 2 þ CuO !…”

Section: Dsc Analysismentioning

confidence: 99%

Improving Contour Accuracy and Strength of Reactive Air Brazed (RAB) Ceramic/Metal Joints by Controlling Interface Microstructure

Kuhn

Brandenberg

et al. 2012

Adv Eng Mater

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Nowadays with a rapid development of high temperature electrochemical devices, sealing technology is an issue of high practical relevance for the applicability of such equipment. Most commonly used joining technologies are glass joining, active metal brazing and reactive air brazing (RAB). [1] Glass joining is a relatively simple and cost-effective bonding method. However, for glass brazed joints, the maximum operation temperature is limited by the softening point of glass. [2,3] Active metal brazing requires a very stringent brazing atmosphere. Such joints have to be processed either under high vacuum or under very clean inert gasatmosphere, what causes comparatively higher processing costs than air-brazing processes. [1] Besides, recent studies also show that after long time operation in air, the active metal braze joints oxidize completely, maintaining little or no strength. [4,5] In an effort to find a cost-effective and stable brazing technique, RAB was developed. [2] Reactive air brazing uses reactive elements, which are at least partially dissolved in a noble metal solvent, to reactively modify the faying surface, such that the newly formed surface is readily wetted by the rest of the molten filler metal. [1] With the increased effort in the development of intermediate temperature SOFC systems, Ag and Ag-based materials for sealing and interconnection have gained increased interest. [6] As a precious metal, Ag possesses good chemical stability and lower costs than other precious metals like platinum and gold.

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“…Health and environmental hazards connected with the use of lead are the reason that the development of high-temperature lead-free solders have become a serious issue at present. The use of lead-free braze fillers also applies to brazing, which is confirmed by authors [5][6][7][8]. Unfortunately, in the case of soldering, there are presently only a limited number of high-temperature, lead-free alloys that would be at least partially capable of replacing high-lead solders [9].…”

Section: Introductionmentioning

confidence: 85%

Direct Ultrasonic Soldering of AlN Ceramics with Copper Substrate Using Zn–Al–Mg Solder

Koleňák

Kostolný

Drápala

et al. 2020

Metals

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This research aims to develop the direct soldering of aluminum nitride (AlN) ceramics with a copper substrate using Zn–Al–Mg solder. The solder type, Zn5Al3Mg, has a close-to eutectic composition with a melting point of 359 °C. The microstructure of Zn–Al–Mg solder is composed of solid solution (Al), solid solution (Zn), an Mg2Zn11 phase and a minority MgZn2 phase. The tensile strength is from 82 to 169 MPa and depends on the magnesium content. The bond with AlN ceramics is formed due to the interaction of active Zn, Al and Mg metals with the substrate surface without forming a new transition phase. Zn and Al elements exert a substantial effect on bond formation with the Cu substrate. Magnesium does not contribute to bond formation with the Cu substrate. Two new phases, CuZn4-ε and Cu33Al17/Cu9Al4/Cu5Zn8- γ, were observed, and form the transition zone of the joint. The maximum shear strength of the AlN/Cu joint fabricated using Zn5Al3Mg solder is 47 MPa. The maximum shear strength of the Cu/Cu joint fabricated using the same solder is 93 MPa.

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Thermochemistry of brazing ceramics and metals in air

Cited by 19 publications

References 7 publications

Characterization of Reactive Air Brazed Ceramic/Metal Joints with Unadapted Thermal Expansion Behavior

Characterization of Reactive Air Brazed Ceramic/Metal Joints with Unadapted Thermal Expansion Behavior

Improving Contour Accuracy and Strength of Reactive Air Brazed (RAB) Ceramic/Metal Joints by Controlling Interface Microstructure

Direct Ultrasonic Soldering of AlN Ceramics with Copper Substrate Using Zn–Al–Mg Solder

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