FG Füge- und Schweißtechnik
Refine
Year of publication
Document Type
- Scientific journal article peer-reviewed (81) (remove)
Way of publication
- Open Access (5)
Keywords
- mechanical properties (8)
- microstructure (6)
- Al – Mg – Si alloy (4)
- Al4043 (2)
- AlSi5 (2)
- Aluminum resistance spot welding (2)
- CO2 methanation (2)
- Ceramic (2)
- Computational welding mechanics (2)
- Distortion analysis (2)
- Electrode water-cooling (2)
- FEM (2)
- Finite element analysis (2)
- Heat transfer (2)
- Virtual manufacturing (2)
- WAAM (2)
- aluminum foam (2)
- cylinder block application (2)
- fatigue strength (2)
- four-point bending (2)
- impulse friction stir welding (2)
- inner diameter coating (2)
- laser welding (2)
- power and frequency of pulses (2)
- structure (2)
- welding (2)
- wire arc additive manufacturing (2)
- 316L (1)
- 3D-Printing (1)
- 3D-printing (1)
- AA2024 (1)
- Additive manufacturing (1)
- Al-Mg-Si alloy (1)
- Al2O3/Cu-O Composites (1)
- Al5356 (1)
- Al5356 alloy (1)
- AlMg5Cr (1)
- AlSi12 (1)
- Arc welding (1)
- Build-up strategy (1)
- CH4 selectivity (1)
- Cold Cracking (1)
- Complex shaped ceramic composites (1)
- Corrosion (1)
- Dissimilar joint (1)
- Dissimilar steel aluminum welding (1)
- EDS measurements (1)
- Elastic-plastic analysis (1)
- Experiment design (1)
- Experimental Testing (1)
- FE simulation (1)
- FE-Simulation (1)
- FE-Simulation des Schweißens (1)
- FE-simulation (1)
- Fluid guiding elements (1)
- GMAW (1)
- Heat source model (1)
- High Strength Steel (1)
- Indentation (1)
- Inherent strain method (1)
- Instrumented experiments (1)
- Kaltriss (1)
- Laser beam build-up welding (1)
- Laser metal deposition (1)
- Laser welding Dissimilar joint Heat source model Finite element analysis Thermal simulation Weld shape (1)
- MAX phases (1)
- Macro-cellular SISIC (1)
- Mechanical (1)
- Mechanical properties (1)
- Microstructure (1)
- Multi-pass weldment (1)
- NbAl3/Al2O3 Composites (1)
- Neutron diffraction (1)
- Non-ferrous metals and alloys (1)
- Physical Simulation (1)
- Pressing and three-dimensional printing (1)
- Pressureless Infiltration (1)
- Reactive Hot Pressing (1)
- Reactive Infiltration (1)
- Reverse analysis (1)
- SLM (1)
- Steel S355 (1)
- Straightening (1)
- Stress distribution (1)
- Structured catalysts (1)
- Submerged are welding (1)
- Thermal Shock Behavior (1)
- Thermal contact conductance (1)
- Thermal simulation (1)
- Thermal straightening (1)
- Thermo-mechanical properties (1)
- Three-dimensional printing (1)
- Triply periodic minimal surfaces (1)
- Wasserstoff- und Stickstoffverteilung (1)
- Weld shape (1)
- Welding simulation (1)
- acicular ferrite (1)
- adhesion strength (1)
- air bending (1)
- air bending, structured sheet metal, simulation (1)
- alumina (1)
- aluminium-steel weld (1)
- aluminum (1)
- aluminum alloy (1)
- aluminum sandwich (1)
- automotive (1)
- bending force (1)
- butt weld (1)
- butt welded joint (1)
- carbon steel (1)
- cgs (1)
- cold arc pulse (1)
- cold arc pulse (CAP) (1)
- cold cracks; finite‐element‐analysis; Kaltrisse (1)
- cold gas spray (1)
- cold gas spraying (CGS) (1)
- cold gas spraying (cgs) (1)
- composite materials (1)
- computational welding mechanics (1)
- computer modeling (1)
- cored wire (1)
- crystallography (1)
- curvilinear seam (1)
- defects formation (1)
- deformation (1)
- dissimilar joint (1)
- electron beam welding (1)
- eutectic formations (1)
- fastest descent method (1)
- fracture behavior (1)
- friction stir welding (1)
- grain structure (1)
- gyroid geometry (1)
- gyroid-3D complex (1)
- hardness (1)
- heat input (1)
- high-alloy steels (1)
- high-speed friction stir welding (HSFSW) (1)
- high-strength steel (1)
- hochfeste Stähle (1)
- hot crack susceptibility (1)
- impulse friction stir welding (IFSW) (1)
- inlayer (1)
- laser beam welding (1)
- laserstrahlgeschweißte Bauteile (1)
- liquation cracks (1)
- metallic foam sandwich (1)
- microhardness (1)
- microscopic chemical analysis (1)
- microstructural characteristics (1)
- microstructure evolution (1)
- modeling of welding and joining (1)
- morphology (1)
- multi-pass welds (1)
- neutron diffraction (1)
- nickel-based alloys (1)
- non-uniformity (1)
- numerische Schweißsimulation,Gefügeumwandlungen,Werkstoffkennwerte (1)
- optimization (1)
- particle velocity (1)
- phase evolution (1)
- physical simulation, Gleeble (1)
- precipitation (1)
- pulse friction stir welding (1)
- remnant oxide line (ROL) (1)
- residual stress (1)
- resistance spot weld (1)
- rsw (1)
- s precipitation (1)
- single-track (1)
- sources method (1)
- stress-strain state (1)
- structur sheet metals (1)
- structured panel (1)
- structured sheet metal (1)
- surfacing (1)
- temperature field (1)
- temperature rates (1)
- tensile properties (1)
- tensile strength (1)
- thermal cycle (1)
- thermal-metallurgical FE simulation (1)
- thermo-mechanical properties (1)
- wear resistance (1)
- welded joint (1)
- welded structures (1)
- welding simulation (1)
- welding temperature field (1)
Institute
In the current paper, the correlation between the physical size of additively built wire arc specimens and their structure and properties is studied. For the purpose of this work, two oval shaped specimens of different lengths were manufactured under the same technological conditions. The specimens have a length of 200 mm and 400 mm and will be referred to as L200 and L400. The microstructure of the samples was studied using X-ray diffraction analysis (XRD), optical microscopy, and scanning electron microscopy (SEM). The microhardness, yield strength (YS), and ultimate tensile strength (UTS) were determined and their correlation with the technological conditions of specimen build-up was clarified. The results of the carried out experiments indicated that the crystallographic structure of both specimens is similar. The scanning electron microscopy images show a higher concentration of irregularly shaped micro-pores formed near the edge of the αAl grains in the structure of the L400 specimen compared to the L200 one. An increase in the size of the αAl solid solution grains in the case of the L200 specimen towards its top section was noticed using optical microscopy. A slightly lower magnitude change was noticed concerning the L400 specimen. The increase in the size of the aluminum crystals was determined to be the increasing interpass temperature. Due to the much smaller thermal dissipation capacity of the smaller specimen, the interpass temperature of the same increased faster compared to the larger specimen. All of the above-mentioned factors led to a decrease in the microhardness of the specimens at higher stages of build-up. Since the specimens were deposited using similar layer deposition conditions, the resultant YS and UTS data are also highly comparable.
The mass production of metallic components requires high agility in the working process conditioned by the necessity of building details of different shapes and sizes. Changing the size of the components theoretically influences the thermal dissipation capability of the same, which could lead to a change in their structure and mechanical properties. This is particularly important when aluminum alloys are concerned. For this reason, two Al5356 single-track specimens were built using the same technological conditions of layer deposition by varying only their geometrical size. In all cases, the specimens were wire and arc additively manufactured (WAAM) using a process based on gas metal arc welding (GMAW) in the cold arc pulse mode (CAP). The structure of both specimens was studied and defects along their surfaces were detected in the form of micro-pores and micro-cracks. A high concentration of undissolved Mg particles was also detected, along with some standalone Si particles. Uniformity in the build-up process was achieved, which led to the formation of nearly identical structures in the specimens. Subsequently, the resultant mechanical properties were also highly comparable. This indicates that the geometry-related variation in thermal conditions has an insignificant influence on the component’s structure and properties.
In this publication, cold gas spraying (CGS) is investigated as an enabler for aluminum-steel joints. Using a powder-based coating process to adhere a steel layer to an aluminum substrate allows a steel component to be welded to the deposited layer by resistance spot welding. This method permits the metallurgical connection between similar materials to be separated, while mechanical bonding ensures the connection at the dissimilar aluminum-to-inlayer interface. A modification of the porous CGS layer, as well as the creation of the remelted zone in the aluminum, can be observed during the resistance spot welding process. Electron backscatter diffraction (EBSD) analyses show that the severely prestressed particles in the CGS coating recrystallize, which coincides with a decrease in defect density and hardness in the heat-affected zone. Microscopy of the aluminum substrate shows the creation of metallurgical pores as well as the expansion of pores attributed to the casting process. The rise in remelted aluminum hardness and decrease in the heat-affected zone of the CGS layer indicate the formation of a metallurgical notch.
Investigations on the thermal conditions during laser beam welding of high-strength steel 100Cr6
(2023)
This study examines the thermal conditions during laser beam welding of 100Cr6 high-strength steel using a TruDisk5000 disc laser with a continuous adjustable power range of 100–5000 W. Two parameter sets, characterized by laser power and welding speeds, were analyzed by thermal-metallurgical FE simulations to determine their impact on the thermal conditions during welding. The results show a significant shift in heat coupling, with conduction transitioning to deep penetration welding. As a result of the high welding speeds and reduced energy input, extremely high heating rates up to 2∙104 K s−1 (set A) respectively 4∙105 K s−1 (set B) occur. Both welds thus concern a range of temperature state values for which conventional Time-Temperature-Austenitization (TTA) diagrams are currently not defined, requiring calibration of the material models through general assumptions. Also, the change in energy input and welding speed causes significantly steep temperature gradients with a slope of approximately 5∙103 K mm−1 and strong drops in the temperature rates, particularly in the heat affected zone. The temperature cycles also show very different cooling rates for the respective parameter sets, although in both cases they are well below a cooling time t8/5 of 1 s, so that the phase transformation always leads to the formation of martensite. Since the investigated parameters are known to cause a loss of technological strength and conditionally result in cold cracks, these results will be used for further detailed experimental and numerical investigation of microstructure, hydrogen distribution, and stress-strain development at different restraint conditions.
For the purpose of this research, single track details were manufactured in the shape of thin walls with a length of 100 mm and a height of 80 mm. Two welding speeds were chosen for this experiment–13.3 mm/s and 20.0 mm/s corresponding to the following heat inputs: 120 J/mm and 80 J/mm. The gas metal arc welding (GMAW) method was used for the build-up of the specimens in the cold arc pulse mode. The structure of the specimens was studied using X-ray diffraction (XRD) analysis carried out with CuKα radiation with a wavelength of 1.5406 Ǻ, optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). Furthermore, the Vickers hardness of the samples was determined using a ZwickRoell DuraScan 10/20 G5 unit at a force of 1 N. A preferred crystallographic orientation towards the (200) plane was observed in all cases, however a vastly textured structure was observed with inclusions of peaks in the (111), (220), and (311) crystallographic planes. The full width at half maximum (FWHM) of samples taken from different stages of build-up was calculated indicating an increase of the dislocation density at the more advanced stages of specimen growth. Despite that an increase of the hardness was observed towards the top of both specimens. This is attributed to the change in the structure of the αAl + Si formations from an irregular one at the bottom of the specimens, towards a fibrous one at the top. The results are discussed in regard to the optimization of the build-up process during wire arc additive manufacturing (WAAM).
Microhardness variations across the friction stir welded (FSW) and impulse friction stir welded (IFSW) AA2024–T351 joints have been elucidated by the transformations of the S–Al2CuMg phase with a special focus on a distinguished hardness peak within the heat-affected zone (HAZ) of the impulse welds. The increase in hardness within the stir zone (SZ) originated from the partial re-precipitation of the initial Guinier-Preston-Bagaryatsky zones (GPB) and metastable S needles, previously dissolved.) Formation and growth of stable S precipitates via coalescence accounted for the softening through the thermo-mechanically affected zone (TMAZ). The peak strengthening within the HAZ of the IFSW joints was mainly caused by the dense needle-shaped S particles, which can be explained by a mutual influence of the process specific temperature and strain cycles. Dislocations and subgrain boundaries introduced to the material due to plastic deformation facilitated the nucleation of strengthening S precipitates in the HAZ. It demonstrates that the impact of deformation should be considered by the characterization of the precipitation development in the HAZ.
The effect of heat treatment at various temperatures (650, 850, 1050, and 1100°C) and dwell times (10 min and 1 h) on the metallurgical and microstructural evolution as well as on the related tensile properties of stainless steel 316L processed by selective laser melting (SLM) has been systematically evaluated. The metallurgical and microstructural features such as defects, stability of the columnar–cellular structure and substructure, second phase particles, and phase transformation imparted by SLM and heat treatment have been discussed. It has been shown that the processing conditions specific to SLM significantly alter the kinetics of phase evolution compared to standard welding techniques which affects the accuracy of the prediction. The influence of these characteristics on tensile properties and hardness was elucidated. It was disclosed that with increasing heat treatment temperature there was a gradual increase in elongation but a decrease in strength related to the dislocation density and the development of the microstructure.
The beam inclination leads to a change in the laser spot size on the material surface. The higher the inclination, the larger the irradiated area and the lower the laser intensity. Moreover, if the material surface is outside of the beam focal plane, the intensity distribution profile becomes asymmetric. In this study, a heat source model, which calculates the intensity distribution on the workpiece surface as a function of beam parameters (beam waist, divergence half-angle) and process parameters (laser power, incidence angle, and distance to focal plane) was developed. The applicability of the heat source model was demonstrated by simulating 4 different laser hardening regimes. Once the heat efficiency coefficient had been calibrated the developed finite-element model allowed computation of temperatures while hardening with perpendicular laser beams as well as with inclined beams. The open-source software FEniCSx was used for the finite element computations. The mathematical formulation, required for performing temperature simulations with FEniCSx was briefly introduced.
Due to the recent developments of hardware components and the hereby resulting ability to increase process parameters, the application area of the cold gas spray technology is expanding quickly. The present
research focuses on the influence of working gas pressure and working gas temperature on the adhesive strength of inner diameter coatings, which were produced with two different alloy steel powder variants. Gas pressure and gas temperature were varied in four different parameter sets. At first, the powder variants were examined for morphology and particle size distribution. Secondly, the influence of
four different process parameters on the achievable particle velocity was measured. In addition, the arithmetical mean height (Sa) of the coating was measured in order to determine the effect of the four parameter sets on the achievable surface roughness. Furthermore, the impact of the process parameters on the steel particles’ penetration
depth into the aluminum substrate was examined. Finally, adhesion strength measurements of the inner diameter coatings were carried out. The results reveal that with rising process parameters, the particle velocity increases, and the achievable surface roughness is lowered. It was also shown that the penetration depth of the particles into
the substrate increases with increasing particle velocity. In addition, this study demonstrated a dependence of the process parameters on the adhesion strength for inner diameter coatings.
3D-printed structured catalysts for CO2 methanation reaction: Advancing of gyroid-based geometries
(2022)
This work investigates the CO2 methanation rate of structured catalysts by tuning the geometry of 3D-printed metal Fluid Guiding Elements (FGEs) structures based on periodically variable pseudo-gyroid geometries. The enhanced performance showed by the structured catalytic systems is mostly associated with the capability of the
FGEs substrate geometries for efficient heat usages. Thus, variations on the channels diameter resulted in ca. 25% greater CO2 conversions values at intermediate temperature ranges. The highest void fraction evidenced in the best performing catalyst (3D-1) favored the radial heat transfer and resulted in significantly enhanced catalytic activity, achieving close to equilibrium (75%) conversions at 400 ◦C and 120 mL/min. For the 3D-1 catalyst, a mathematical model based on an experimental design was developed thus enabling the estimation of its behavior as a function of temperature, spatial velocity, hydrogen to carbon dioxide (H2/CO2) ratio, and inlet CO2 concentration.
Its optimal operating conditions were established under 3 different scenarios: 1) no restrictions, 2) minimum H2:CO2 ratios, and 3) minimum temperatures and H2/CO2 ratio. For instance, for the lattest scenario, the best CO2 methanation conditions require operating at 431 ◦C, 200 mL/min, H2/CO2 = 3 M ratio, and inlet CO2 concentration = 10 %.