scholarly journals Cracking of Copper Brazed Steel Joints Due to Precipitation of MnS upon Cooling

2020 ◽  
Vol 29 (12) ◽  
pp. 8183-8193
Author(s):  
Dheeraj Varanasi ◽  
Daniel Koncz-Horvath ◽  
Anna Sycheva ◽  
Peter Baumli ◽  
George Kaptay
Keyword(s):  
High Vacuum ◽  
Holding Time ◽  
Critical Conditions ◽  
Pure Liquid ◽  
Steel Grades ◽  
Heat Expansion ◽  
Mn Content ◽  
Expansion Coefficients ◽  
Time Required ◽  
Steel Joints

AbstractThe process of brazing of different steel grades by pure liquid copper foil was studied to reveal the critical conditions when cracks do or do not appear in the braze upon cooling without any external load. Steel grades C45 (S 0.030 wt.%, no Mn and no Cr), S103 (Mn 0.25 wt.% and S 0.020 wt.% with no Cr), CK60 (0.75 wt.% Mn, 0.07 wt.% S and 0.15 wt.% Cr) and EN 1.4034 (Cr 12 wt.%, Mn 1.0 wt.% and S 0.035 wt.%) are studied under identical conditions using copper foils of 70-microns-thick. The samples were held above the melting point of copper at 1100 °C under high vacuum for different time durations (between 180 and 3600 s) and then cooled spontaneously. The joints were found cracked during cooling after a certain critical holding time. This critical holding time for cracking was found to decrease with increasing the Mn content and the S content of steel. It is observed that cracking is due to the precipitation of a critical amount of MnS phase upon cooling. The MnS/Cu interface is the weakest interface in the joint (with adhesion ensured only by van-der-Waals bonds), which is broken/separated upon cooling due to difference in heat expansion coefficients of the sulfide and copper phases. Higher is the Mn and S content, shorter is the probable time required for crack to appear in the joint. The braze integrity diagram is constructed as function of solubility product of MnS in steel and holding time showing a stable crack-free technological region and an unstable technological region with high probability of crack formation.

Effect of holding time on the microstructure and strength of tungsten/steel joints by HIP diffusion bonded using a Cu interlayer

2020 ◽  
Vol 261 ◽  
pp. 126875 ◽  
Author(s):  
Jiajia Zhang ◽  
Donghua Xie ◽  
Qishou Li ◽  
Chunli Jiang ◽  
Qiang Li
Keyword(s):  
Holding Time ◽  
Steel Joints ◽  
Cu Interlayer ◽  
Tungsten Steel

Microstructure and Strength of Alumina-Metal Joint Brazed by Activated Molybdenum–Manganese Method

2007 ◽  
Vol 353-358 ◽  
pp. 2049-2052 ◽  
Author(s):  
Gui Wu Liu ◽  
Guan Jun Qiao ◽  
Hong Jie Wang ◽  
Zhi Hao Jin
Keyword(s):  
Cooling Rate ◽  
Joint Strength ◽  
Shear Loading ◽  
Holding Time ◽  
Slow Heating ◽  
Heating And Cooling ◽  
Migration Direction ◽  
Process Factors ◽  
Seal Strength ◽  
Steel Joints

High purity alumina/stainless steel joints were produced via activated molybdenummanganese (Mo-Mn) route using 72Ag-28Cu solder. Microstructures of the metallized ceramic and joint sections were observed by scanning electron microscopy. Joint strength was tested by shear-loading method. Some process factors were characterized and analyzed, which include temperature, holding time and heating and cooling rate in ceramic metallization process. The effects of Ni plating and succedent annealing were also investigated. Experimental results show that, migration of glassy phases is the main mechanism of the ceramic metallization. Glass migration direction is from metallizing layer to ceramic side. In the ranges of temperature and holding time of metallization, joint strength firstly increases and then falls with temperature raising and time extending. More fully sintered metallizing layer can be obtained while the temperature increases from 1200oC to 1500oC, and the time prolongs from 30min to 60min. Over-sintering of the metallizing layer will take place with metallizing temperature of 1600 oC and overlong holding time of 70min, which reduces the joint strength. The slower heating and cooling rate, and the annealing after Ni plating both help enhance the seal strength, due to relieving or eliminating interlayer residual thermal stress. However, too slow heating and cooling rate, such as 5 oC /min, is equivalent to overlong holding time and finally also decline the strength. A thin Ni coating helps solder wet metallizing surface, and stops solder erode metallizing layer.

A High Vacuum Scanning Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 422-423
Author(s):  
W. R. Bottoms
Keyword(s):  
Electron Microscope ◽  
Chemical Composition ◽  
Scanning Electron Microscope ◽  
High Vacuum ◽  
Electron Source ◽  
Electron Gun ◽  
Vacuum System ◽  
Contamination Rate ◽  
Time Required ◽  
Scanning Electron

The vacuum system of any electron optical instrument effects the contamination rate, electron source life, the quality of the electron source which can be employed, vibration amplitudes and stray magnetic field levels. It is particularly important for the scanning electron microscope where the object of primary interest is a specimen surface which can be altered by contamination. If we extend our investigations to employ Auger electron spectroscopy for surface chemical analysis, the requirements on the vacuum system are much more stringent. It is necessary that the chemical composition of the surface monolayer is not appreciably altered during the time required to take Auger spectra. The vacuum level required to accomplish this is dependent on the specimen material and the chemical composition of the ambient gas.Commercially available equipment can be modified to provide a vacuum environment maximizing the analytical capabilities of the instrument. The gas loads from the specimen and electron gun chambers of the instrument are minimized by utilizing only materials with favorable outgassing rates, and employing a gentle bakeout to remove water and other loosely bound gases on the system surfaces.

Nanostructured Cd1−xMnxS Films for Spintronics and Optoelectronic Device Applications: Synthesis and Characterization

2008 ◽  
Vol 8 (12) ◽  
pp. 6487-6490
Author(s):  
D. Sreekantha Reddy ◽  
B. K. Reddy ◽  
K. R. Gunasekhar ◽  
P. Sreedhara Reddy
Keyword(s):  
Thermal Evaporation ◽  
High Vacuum ◽  
Optoelectronic Device ◽  
Synthesis And Characterization ◽  
Glass Substrates ◽  
Structure Morphology ◽  
Device Applications ◽  
Mn Content ◽  
Optical And Magnetic Properties ◽  
Composition Structure

Nanostructured Cd1−xMnxS (x = 0.3 and 0.4) films were prepared on glass substrates by thermal evaporation. All the films were deposited at 373 K and annealed at 473 K in high vacuum of 2 × 10−6 mbar. The nanostructure films were characterized for composition, structure, morphology, optical and magnetic properties. All the films exhibited wurtzite structure of the host CdS material. AFM studies showed that all the films were in nanocrystalline form with the grain size varying in the range of 25–43 nm. The magnetic susceptibility increased sharply with Mn content 'x'.

scholarly journals Effect of Manganese on the Structure-Properties Relationship of Cold Rolled AHSS Treated by a Quenching and Partitioning Process

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1122 ◽  
Author(s):  
Simone Kaar ◽  
Daniel Krizan ◽  
Reinhold Schneider ◽  
Coline Béal ◽  
Christof Sommitsch
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Bainitic Ferrite ◽  
Total Elongation ◽  
Process Window ◽  
Quenching And Partitioning ◽  
Strain Behavior ◽  
Strain Induced Martensite ◽  
Steel Grades ◽  
Mn Content

The present work focuses on the investigation of both microstructure and resulting mechanical properties of different lean medium Mn Quenching and Partitioning (Q&P) steels with 0.2 wt.% C, 1.5 wt.% Si, and 3–4 wt.% Mn. By means of dilatometry, a significant influence of the Mn-content on their transformation behavior was observed. Light optical and scanning electron microscopy (LOM, SEM) was used to characterize the microstructure consisting of tempered martensite (α’’), retained austenite (RA), partially bainitic ferrite (αB), and final martensite (α’final) formed during final cooling to room temperature (RT). Using the saturation magnetization measurements (SMM), a beneficial impact of the increasing Mn-content on the volume fraction of RA could be found. This remarkably determined the mechanical properties of the investigated steels, since the larger amount of RA with its lower chemical stabilization against the strain-induced martensite transformation (SIMT) highly influenced their overall stress-strain behavior. With increasing Mn-content the ultimate tensile strength (UTS) rose without considerable deterioration in total elongation (TE), leading to an enhanced combination of strength and ductility with UTS × TE exceeding 22,500 MPa%. However, for the steel grades containing an elevated Mn-content, a narrower process window was observed due to the tendency to form α’final.

Effects of Annealing Parameters on Recrystallization of AZ31 Magnesium Alloy Processed by Continuous Rheo-Extrusion

2011 ◽  
Vol 239-242 ◽  
pp. 15-20
Author(s):  
Ren Guo Guan ◽  
Zhan Yong Zhao ◽  
Fu Rong Cao ◽  
Hong Qian Huang ◽  
Chun Guang Dai ◽  
...  
Keyword(s):  
Growth Rate ◽  
Magnesium Alloy ◽  
Grain Growth ◽  
Annealing Temperature ◽  
Holding Time ◽  
Az31 Magnesium Alloy ◽  
Dislocation Densities ◽  
Recrystallized Grain Size ◽  
Lower Temperature ◽  
Time Required

AZ31 magnesium alloy profiles were prepared by continuous rheo-extrusion, and effects of annealing temperature and time on recrystallization of AZ31 magnesium alloy were investigated. The results reveal that when the profile is annealed in the temperature range from 200°C to 300°C, the moving velocity of grain interface with different dislocation densities on both sides increases with increasing annealing temperature, which is favorable to the formation of crystallized nucleus in the region in which interface sweeps over. As a result, the time required by the accomplishment of recrystallization becomes short. After recrystallization finishes, continuous temperature rise or prolonged holding time result in grain growth. When the profile is annealed at elevated temperature, with the prolongation of holding time, the grain growth rate accelerates obviously, and hence recrystallized microstructure becomes coarse. When the profile is annealed at lower temperature, the grain growth rate becomes small, and the time required by the accomplishment of recrystallization is long, but recrystallized microstructure is fine and homogeneous. When the profile is annealed at 250°C for 4h, average recrystallized grain size is 15μm.

scholarly journals Prediction of the Shear Tension Strength of Resistance Spot Welded Thin Steel Sheets from High- to Ultrahigh Strength Range

2021 ◽  
Author(s):  
Kornél Májlinger ◽  
Levente T. Katula ◽  
Balázs Varbai
Keyword(s):  
High Strength Steel ◽  
Welding Process ◽  
High Strength ◽  
Professional Literature ◽  
Resistance Spot ◽  
Base Materials ◽  
Ultra High Strength Steel ◽  
Steel Grades ◽  
Steel Joints ◽  
Tension Strength

The tensile strength of newly developed ultra-high strength steel grades is now above 1800 MPa, and even new steel grades are currently in development. One typical welding process to join thin steels sheets is resistance spot welding (RSW). Some standardized and not standardized formulas predict the minimal shear tension strength (STS) of RSWed joints, but those formulas are less and less accurate with the higher base materials strength. Therefore, in our current research, we investigated a significant amount of STS data of the professional literature and our own experiments and recommended a new formula to predict the STS of RSWed high strength steel joints. The proposed correlation gives a better prediction than the other formulas, not only in the ultra-high strength steel range but also in the lower steel strength domain.

Development of Self-Supporting Polycrystalline Diamond Bridge

2007 ◽  
Vol 537-538 ◽  
pp. 145-150
Author(s):  
Hajnalka Csorbai ◽  
Gergely Kovách ◽  
P. Fürjes ◽  
P. Csíkvári ◽  
A. Sólyom ◽  
...  
Keyword(s):  
Industrial Application ◽  
Polycrystalline Diamond ◽  
Diamond Structure ◽  
Mechanical Tension ◽  
Etching Technique ◽  
Sio2 Substrate ◽  
Microwave Assisted ◽  
Cvd Method ◽  
Heat Expansion ◽  
Expansion Coefficients

Polycrystalline diamond layers are mostly used in various fields of industrial application. Mechanical tension is generated due to the different heat expansion coefficients of the substrate and the layer, which leads to fracturing in some cases. In this work a homogeneous polycrystalline diamond structure has been deposited on Si/SiO2 substrate by microwave assisted CVD method (MW-PECVD). An selective etching technique has been used to remove the silicon below the 2.5 micron thick diamond layer. A self-supporting diamond structure has been created this way. Polycrystalline diamond based heaters and thermometers can be made from doped diamond materials, which can resist corrosive and radiative environment.

scholarly journals Model for Predicting and Analyzing the %Fe Removed as Deleterious Element from Al-Si alloys During Fe Removal Processing with Mn

2016 ◽  
Vol 2 (6) ◽  
pp. 125
Author(s):  
F. A. Anene ◽  
N. E. Nwankwo
Keyword(s):  
Standard Deviation ◽  
Standard Error ◽  
Model Equation ◽  
Processing Parameters ◽  
Holding Time ◽  
Experimental Result ◽  
Close Proximity ◽  
Mn Content ◽  
The Difference ◽  
Cubic Function

Model equation for predicting and analysing %Fe removed from a eutectic Al-Si alloy during Fe removal processing with Mn under controlled conditions has been derived and validated. The model derived;%Fe removed = +1.30700 + 0.095882* Al-Si + %Mn - 0.068512* Al-Si + %Mn^2 + 9.77000E-003* Al-Si+%Mn^3 ,is found to predict the %Fe removed from Al-Si alloy as a cubic function of Mn content. With a standard deviation of 0.010. Analysed results obtained show that %Fe removal equation with Mn addition has been validly derived. The model " R-Squared" of 0.9814 is found to be in agreement with the "Adj R-Squared" of 0.9628; the difference being less than 0.2. The derived model equation gives a reasonable forecast of %Fe removed very close to the values obtained from the experiments. The close proximity of both model and experimental result values is attributed to the low standard error of the model coefficients. The processing parameters are process temperature, alloy contents and holding time.

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