scholarly journals Interface Reactions Responsible for Run-Out in Active Brazing: Part 4

2022 ◽  
Vol 101 (1) ◽  
pp. 1-14
Author(s):  
PAUL T. VIANCO ◽  
◽  
CHARLES A. WALKER ◽  
DENNIS DE SMET ◽  
ALICE KILGO ◽  
...  
Keyword(s):  
Reaction Layer ◽  
Driving Force ◽  
Sessile Drop ◽  
Effective Means ◽  
Interface Reaction ◽  
Base Material ◽  
Test Sample ◽  
Interface Reactions ◽  
Braze Joint ◽  
Filler Metals

This study examined the interface reaction between Ag-xAl filler metals having x = 0.2, 0.5, or 1.0 wt-% and Kovar™ base materials. The present investigation used the braze joint test sample configuration. The brazing conditions were 965°C (1769°F), 5 min; 995°C (1823°F), 20 min, and a vacuum of 10–7 Torr. Run-out was absent from all test samples. Combining these results with those of the Part 2 study that used high-Al, Ag-xAl filler metals (x = 2.0, 5.0, and 10 wt-%) established these conditions for run-out: Ag-xAl filler metals having x ≥ 2.0 wt-% Al, which result in reaction layer compositions, and (Fe, Ni, Co)y Alz , having z ≥ 26 at.-% Al. The limited occurrences of run-out lobes resulted from the surface tension effect that quickly reduced the driving force for additional run-out events. The interface reactions were controlled by a driving force that was an expressed function of filler metal composition (Ag-xAl) and brazing temperature, as opposed to simply thermally activated rate kinetics. The differences of reaction layer composition and thickness confirmed that the interface reactions differed between the braze joint and sessile drop configurations. Collectively, the findings from the Parts 1–4 investigations concluded that the most-effective means to mitigate run-out is to place a barrier coating on the Kovar base material that will prevent formation of the (Fe, Ni, Co)y Alz reaction layer.

scholarly journals Interface Reactions Responsible for Run-Out in Active Brazing: Part 3

2021 ◽  
Vol 100 (12) ◽  
pp. 379-395
Author(s):  
PAUL T. VIANCO ◽  
◽  
CHARLES A. WALKER ◽  
DENNIS DE SMET ◽  
ALICE KILGO ◽  
...  
Keyword(s):  
Reaction Layer ◽  
Chemical Potential ◽  
Filler Metal ◽  
Sessile Drop ◽  
Interface Reaction ◽  
Base Material ◽  
Mitigation Strategies ◽  
Interface Reactions ◽  
Rate Kinetics ◽  
Sessile Drops

This study examined the interface reaction between sessile drops of the Ag-xAl filler metals having x = 0.2, 0.5, and 1.0 wt-% and KovarTM base material as an avenue to understand the run-out phenomenon observed in active filler metal braze joints. The brazing conditions were combinations of 965°C (1769°F) and 995°C (1823°F) temperatures and brazing times of 5 and 20 min. All brazing was performed in a vacuum of 10–7 Torr. Microanalysis confirmed that a reaction layer developed ahead of the filler metal to support spontaneous wetting and spreading activity. However, run-out was not observed with the sessile drops because the additional surface energy created by the sessile drop free surface constrained wetting and spreading. The value of z in the reaction layer composition, (Fe, Ni, Co)yAlz, increased with x of the Ag-xAl sessile drops for both brazing conditions. Generally, the values of z were lower for the more severe brazing conditions. Also, the reaction layer thickness increased with the Al concentration in the filler metal but did not increase with the severity of brazing conditions. These behaviors indicate that the interface reaction was controlled by the chemical potential rather than the rate kinetics of a thermally activated process. The determining metrics were filler metal composition (Ag-xAl) and brazing temperature. The findings of the present study provided several insights toward developing potential mitigation strategies to prevent run-out.

Investigations on Interface Reactions and Wettability between Melt Superalloys and Ceramic Materials

2016 ◽  
Vol 703 ◽  
pp. 132-137 ◽  
Author(s):  
Xiao Yan Chen ◽  
Fei Li ◽  
Jun Wang ◽  
Bao De Sun
Keyword(s):  
Ceramic Material ◽  
Sessile Drop ◽  
Active Element ◽  
Interface Reaction ◽  
Ceramic Materials ◽  
Wetting Angle ◽  
Reactive System ◽  
Reaction Products ◽  
Interface Reactions ◽  
Sessile Drop Experiment

Interface reactions and wettability between melt superalloys and ceramic mould materials were investigated by using a sessile drop experiment. The wetting angle of the melt alloy on the ceramic material was calculated and the microstructure of the alloy interface was investigated by metalloscope as well as SEM. It was found that active element C in the alloy is an important factor that influences the interface reactions and the wettability. Alloys with C content lower than 0.07wt.% were almost stable on the ceramic material and no interface reaction products were found. However, alloys with C content higher than 0.16wt.% reacted with the ceramic materials. Purple reaction products were found on the alloy surface and sand adhesions were observed at the alloy-ceramic interface. In the non-reactive system, the wetting angle is in the range of 135o-150o. In the reactive system, the wetting angle is lower than 120o.

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

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 727
Author(s):  
Bofang Zhou ◽  
Taohua Li ◽  
Hongxia Zhang ◽  
Junliang Hou
Keyword(s):  
Interfacial Reaction ◽  
Reaction Layer ◽  
Chemical Potential ◽  
Filler Metal ◽  
Diffusion Constant ◽  
Interface Reaction ◽  
Diffusion Path ◽  
Interface Behavior ◽  
Interfacial Reaction Layer ◽  
Sic Ceramic

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·s1/2) 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.

Solidification and Interface Reaction of Titanium Alloys in the BaZrO3 Shell-Mould

2015 ◽  
Vol 828-829 ◽  
pp. 106-111 ◽  
Author(s):  
Chong He Li ◽  
Jin He ◽  
Chao Wei ◽  
Hong Bin Wang ◽  
Xiong Gang Lu
Keyword(s):  
Titanium Alloy ◽  
Investment Casting ◽  
Interface Reaction ◽  
Base Material ◽  
Tini Alloy ◽  
The Novel ◽  
Coarse Powder ◽  
Elemental Diffusion ◽  
Shell Mould ◽  
Mould Base

The investment casting technology is one of the major methods to produce the parts of the titanium due to its low production cost. However, the high activity of titanium melt gives rise to the requirement of high chemical stability of shell materials, to avoid or decrease the interfacial reaction between the mould and the melt. In this paper, a novel BaZrO3 – coated Al2O3 shell was first introduced to the investment casting of titanium alloy. The grain size and baking temperature on the properties of the novel mould were investigated, and then the Ti6Al4V and TiNi alloys were successfully casted by means of this shell. The alloy-mould interaction was discussed. The results showed that the mould achieve high mechanical properties when the content of coarse powder was 50% after sintering 4 hours under 1500°C, and the BaZrO3 coating exhibited an effective barrier to avoid the direct contact between the mould base material and the melt, the thickness of reaction layer of TiNi alloy was about 8 μm, and 17 μm to Ti6Al4V alloy, no refractory particles and elemental diffusion were observed inside the metal. This may imply that BaZrO3 is a promising candidate material for the investment casting of titanium alloy.

scholarly journals Influence of static strength on the fatigue resistance of welds

2018 ◽  
Vol 165 ◽  
pp. 13010 ◽  
Author(s):  
Ceferino Steimbreger ◽  
Nenad Gubeljak ◽  
Norbert Enzinger ◽  
Wolfgang Ernst ◽  
Mirco Chapetti
Keyword(s):  
Crack Length ◽  
Driving Force ◽  
Base Material ◽  
Initial Crack ◽  
Static Strength ◽  
Resistance Curve ◽  
Weld Geometry ◽  
Curve Method ◽  
Mechanic Approach ◽  
Local Properties

The present paper deals with a fracture mechanic approach that employs the Resistance-Curve concept, in order to predict fatigue endurances of welded components, with different tensile strengths of the base metal. The Resistance-Curve method compares the total driving force applied to a crack with its threshold for propagation, both defined as a function of crack length. The former depends on load scheme and weld geometry and it can be obtained from finite element analyses, while the second is inherently related to weld resistance. Results obtained herein showed that threshold curve shape is changed when static strength of the base material is modified. Consequently, its interaction with the driving force differed, giving raise to different fatigue endurances for various values of the tensile strength. However, this effect is only likely to be leveraged, provided that the initial crack length is small enough. In real welded structures, the presence of defects demands longer initial crack lengths to be used in calculations, at which the benefit of enhanced strength is minimised or even inverted. Moreover, at these lengths, the growing process is mainly controlled by weld geometry and long crack propagation threshold, whereas local properties become less important in fatigue limit prediction.

Immiscible Two-Phase Parallel Microflow and Its Applications in Fabricating Micro- and Nanomaterials

2021 ◽  
pp. 200-224
Author(s):  
Yujie Li ◽  
Jie Wang ◽  
Shijie Wang ◽  
Di Li ◽  
Shan Song ◽  
...  
Keyword(s):  
Driving Force ◽  
Water Systems ◽  
Liquid Interface ◽  
Parallel Flow ◽  
Two Phase ◽  
Friction Resistance ◽  
Interface Reactions ◽  
Oil Water ◽  
Proper Balance

The immiscible two-phase flow behaves nonlinearly, and it is a challenging task to control and stabilize the liquid-liquid interface. Parallel flow forms under a proper balance between the driving force, the friction resistance, and the interfacial tension. The liquid-solid interaction as well as the liquid-liquid interaction plays an important role in manipulating the liquid-liquid interface. With vacuum-driven flow, long and stable parallel flow is possible to be obtained in oil-water systems and can be used for fabricating micro- and nanomaterials. Ultra-small Cu nanoparticles of 4~10 nm were synthesized continuously through chemical reactions taking place on the interface. This makes it possible for in situ synthesis of conductive nanoink avoiding oxidation. Well-controlled interface reactions can also be used to produce ultra-long sub-micro Cu wires up to 10 mm at room temperature. This method provided new and simple additive fabrication methods for making integrated microfluidic devices.

Interface Reaction Thermodynamics of AgCuTi Brazing Filler Metal and Alumina Ceramic

2014 ◽  
Vol 936 ◽  
pp. 1239-1246
Author(s):  
Hong Long Ning ◽  
Lin Feng Lan ◽  
Lei Wang ◽  
Jun Biao Peng ◽  
Zhi Jian Peng ◽  
...  
Keyword(s):  
Filler Metal ◽  
Interface Reaction ◽  
Liquid Solution ◽  
Product Formation ◽  
Influential Factor ◽  
Free Energies ◽  
The Real ◽  
Interface Reactions ◽  
Thermodynamics And Kinetics ◽  
Reaction Thermodynamics

In this work, the interface reaction between Al2O3 ceramic and Ag70.5Cu27.5Ti2 brazing filler metal at 845-860°C was investigated. Based on the data of thermodynamics and kinetics, the Gibbs free energies of the main interface reactions in the real brazing system condition were calculated. But the values of normal equilibrium reaction condition and the real interface reaction brazing system were different; and the main influential factor was the brazing temperature, and the system vacuum of brazing condition can lead the change of equilibrium constant (Kα). The results revealed that the high temperature and vacuum active brazing is a non-equilibrium interface reaction especially to titanium alloy, the vacuum and alloy liquid solution are beneficial to the brazing process, and the by-product formation of titanium-oxygen are affected by the diffusion process.

Grain Boundary Diffusion Controlled Precipitation as a Model For thin Film Reactions

1993 ◽  
Vol 311 ◽  
Author(s):  
K. Barmak ◽  
K.K. Coffey
Keyword(s):  
Thin Film ◽  
Driving Force ◽  
Boundary Diffusion ◽  
Chemical Potential ◽  
Driving Forces ◽  
Transport Model ◽  
Interface Reaction ◽  
Grain Structure ◽  
Phase Selection ◽  
Reaction Barriers

ABSTRACTIn order to arrive at a model for nucleation in the reaction of polycrystalline thin films, we have made use of a transport model that combines atom transport across interface reaction barriers with transport along grain boundaries. Through this transport model, the boundary chemical potential, μIi, and a characteristic length Li for each specie are defined. Li and the ratio of grain size to Li determine the spatial variation and the time evolution of the boundary chemical potential respectively. Nucleation of the product phase is modeled as a process whose driving force is determined by these position dependent (and time dependent) boundary chemical potentials. Thus thin film reactions become similar to precipitation from bulk homogeneous supersaturated solid solutions. Numerical calculations, however, show that boundary diffusion results in low “effective” driving forces for nucleation which can lead to heterogeneous nucleation of even the first phase. The model provides a new approach to phase selection by re-evaluation of the driving force and considers the effect of product and reactant grain structure to be fundamental to the reaction process.

Study on Interface Reactions between Nb-Si System In Situ Composite and Ceramics

2007 ◽  
Vol 546-549 ◽  
pp. 1495-1500
Author(s):  
Jing Jing Yu ◽  
Shu Suo Li ◽  
Ya Fang Han
Keyword(s):  
Elevated Temperature ◽  
Interface Reaction ◽  
Vacuum Arc ◽  
In Situ Composite ◽  
Interface Reactions ◽  
Arc Melting ◽  
Reaction Zones ◽  
C And N ◽  
Face Coat

A Nb-Si system in-situ composite Nb-16Si-24Ti-6Cr-6Al-2Hf(at%) was fabricated using vacuum arc melting method, and then was metallurgically reacted with four kinds of ceramics ZrO2, Y2O3 stabilized ZrO2, Y2O3, SiC+Si3N4 at elevated temperature. The microstructures in the interface reaction zones were investigated by SEM and EDS. The results showed that different extent chemical reactions between the composite and these four kinds of ceramics took place. It has been found that HfO2 riched layer formed near the interfaces between the Nb-Si in-situ composite and three ceramics of ZrO2, Y2O3 stabilized ZrO2 and Y2O3, and thickness of the reaction zones were about 100μm, 10μm, 1μm respectively. C and N elements in SiC+Si3N4 ceramic diffused to the composite at elevated temperature, and a new phase that rich of Ti, C and N elements appeared nearby the interface and accumulated inhomogenously. It may be concluded that the interface reactions of both ZrO2 and SiC+Si3N4 with Nb-Si composite were very violent, therefore they are not suitable as face-coat materials of shell molds for investment casting; the interface reaction of Y2O3 stabilized ZrO2 and Nb-Si composite was slighter than ZrO2 and SiC+Si3N4, and it can be used as face-coat material of shell molds, the interface reaction of Y2O3 and Nb-Si composite was very slight, and is recommended as an ideal face-coat materials of shell molds.

Reactive wetting of polycrystalline TiC by molten Zr55Cu30Al10Ni5 metallic glass alloy

2009 ◽  
Vol 24 (7) ◽  
pp. 2420-2427 ◽  
Author(s):  
Ping Shen ◽  
Qiaoli Lin ◽  
Qichuan Jiang ◽  
Hidetoshi Fujii ◽  
Kiyoshi Nogi
Keyword(s):  
Metallic Glass ◽  
Reaction Layer ◽  
Triple Junction ◽  
Sessile Drop ◽  
Contact Angles ◽  
Sessile Drop Method ◽  
The Other ◽  
Reactive Wetting ◽  
Exponential Functions ◽  
Glass Alloy

The isotherm wetting and spreading behaviors of polycrystalline TiC by molten Zr55Cu30Al10Ni5 alloy were investigated at 1133 to 1253 K in a vacuum by using a modified sessile drop method. The system displays good wettability with the initial and final stable contact angles of 44 to 50° and 10 to 14°, respectively, mildly depending on the temperature. The spreading kinetics follows well defined exponential functions and could be described by a molecular dynamic model. On the other hand, a ZrC reaction layer was formed at the interface. The wetting was primarily promoted by the Zr adsorption at the triple junction and then by the formation of the reaction layer.

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