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.

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 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.

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.

scholarly journals Effect of Brazing Parameters on the Microstructure and Properties of SiC Ceramic Joint with Zr-Cu Filler Metal

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 93
Author(s):  
Bofang Zhou ◽  
Jinfeng Wang ◽  
Keqin Feng ◽  
Yuchen Cai ◽  
Sitan Chen
Keyword(s):  
Shear Strength ◽  
Reaction Layer ◽  
Shear Test ◽  
Filler Metal ◽  
Interface Reaction ◽  
Fracture Morphology ◽  
Holding Time ◽  
Sic Ceramic ◽  
Maximum Shear Strength ◽  
Joint Reaction

The microstructure and mechanical properties of brazing SiC ceramic with Zr-Cu filler metal under different brazing parameters (brazing temperature, holding time) were investigated. The phase of the joint reaction interface between Zr-Cu filler metal and SiC ceramic was characterized by XRD, the microstructure and fracture morphology of the brazing SiC ceramic joint were analyzed by SEM with EDS, and the strength of the joint was evaluated by compression shear test. The results show that the brazing join between SiC ceramic and Zr-Cu filler metal can be realized at the brazing temperature of 1100 °C~1300 °C, and the main products of interface reaction are ZrC and Zr2Si. The shear strength of the joint increases with the brazing temperature, and reaches the highest at 1200 °C. The thickness of interface reaction layer increases with the increase of holding time at brazing temperature of 1200 °C. Thickness of the interface reaction layer is 2.9 μm when the joint is holding for 20 min, and the maximum shear strength of the corresponding brazed SiC ceramic joint is 57 MPa.

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.

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 Vacuum Brazing of 55 vol.% SiCp/ZL102 Composites Using Micro-Nano Brazing Filler Metal Fabricated by Melt-Spinning

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1470
Author(s):  
Dechao Qiu ◽  
Zeng Gao ◽  
Xianli Ba ◽  
Zhenjiang Wang ◽  
Jitai Niu
Keyword(s):  
Melt Spinning ◽  
Filler Metal ◽  
Aluminum Matrix ◽  
Chemical Properties ◽  
Base Material ◽  
Fracture Morphology ◽  
Aluminum Matrix Composites ◽  
Joint Shear Strength ◽  
Vacuum Brazing ◽  
Sic Particles

The joining methods of Aluminum matrix composites reinforced with SiC particles (SiCp/Al MMCs) are a challenge during the manufacturing process due to the significant differences between SiC particles and base aluminum in terms of both physical and chemical properties. Micro-nano brazing filler metal Al-17.0Cu-8.0Mg fabricated by melt-spinning technology was employed to deal with the joining problem of 55 vol.% SiCp/ZL102 composites in this work. The result indicated that the foil-like brazing filler metal contained uniformed cellular nano grains, with a size less than 200 nm. The solidus and liquidus temperatures of the foil-like brazing filler metal decreased by 4 °C and 7 °C in comparison with the values of the as-cast brazing filler metal due to the nanometer size effect. The maximum joint shear strength of 98.17 MPa achieved with a brazing temperature of 580 °C and holding time of 30 min was applied in vacuum brazing process. The width of the brazing seam became narrower and narrower with increasing brazing temperature owning to the strong interaction between the micro-nano brazing filler metal and 55 vol.% SiCp/ZL102 composites. The fracture morphology of the joint made at a brazing temperature of 580 °C was characterized by quasi-cleavage fracture. After brazing, the chemical concentration gradient between the brazing filler metal and base material disappeared.

The shape evolution of liquid droplets in miscible environments

2018 ◽  
Vol 852 ◽  
pp. 422-452 ◽  
Author(s):  
Daniel J. Walls ◽  
Eckart Meiburg ◽  
Gerald G. Fuller
Keyword(s):  
Sessile Drop ◽  
Liquid Droplet ◽  
Leading Edge ◽  
Numerical Approach ◽  
Shape Evolution ◽  
Liquid Droplets ◽  
Miscible Liquids ◽  
Experimental Findings ◽  
Sessile Drops ◽  
Pendant Drops

Miscible liquids often come into contact with one another in natural and technological situations, commonly as a drop of one liquid present in a second, miscible liquid. The shape of a liquid droplet present in a miscible environment evolves spontaneously in time, in a distinctly different fashion than drops present in immiscible environments, which have been reported previously. We consider drops of two classical types, pendant and sessile, in building upon our prior work with miscible systems. Here we present experimental findings of the shape evolution of pendant drops along with an expanded study of the spreading of sessile drops in miscible environments. We develop scalings considering the diffusion of mass to group volumetric data of the evolving pendant drops and the diffusion of momentum to group leading-edge radial data of the spreading sessile drops. These treatments are effective in obtaining single responses for the measurements of each type of droplet, where the volume of a pendant drop diminishes exponentially in time and the leading-edge radius of a sessile drop grows following a power law of $t^{1/2}$ at long times. A complementary numerical approach to compute the concentration and velocity fields of these systems using a simplified set of governing equations is paired with our experimental findings.

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