Tensile Strength Of Welded Joints Research Articles

Microstructure evolution and tensile strength of Al/Cu inertia friction welded joint

To save production costs and reduce the weight of structures, it is one of the common ways to replace copper (Cu) with aluminum (Al) in some industries such as the refrigeration industry. The high-quality welding of Al to Cu determines the application of the Al/Cu hybrid structure. The inertia friction welding process was used to weld Al pipe to Cu pipe and the Taguchi experiment method was used to study the effects of inertia friction welding parameters on the mechanical properties of the welded joints, and the results show that the initial speed has the greatest influence on the tensile strength of welded joints. Meanwhile, the analyses of the microstructures of the joint show that Al–Cu IMCs formed at the friction interface to realize the metallurgical bonding of the welded joints. The formation sequence of Al–Cu IMCs in the friction welding process is Al2Cu, Al4Cu9, and AlCu. Whereas the type and thickness of IMCs are closely related to the tensile strength of the joints. When the welded joint forms Al2Cu and Al4Cu9, the interfacial misfit between the IMCs layer and base materials is minimized and the tensile strength of the joint is optimized.

Monitoring of thermo-cycles in fibre laser welding of duplex stainless steel 2205 sheets and its correlation with microstructures and mechanical properties

The study reports the influence of change in the heat supplied (43 J mm−1 to 18.5 J mm−1) on the microstructures as well as mechanical properties of weld joints obtained by welding of Duplex stainless steel 2205 using fibre laser. In-process thermal monitoring of the molten weld pool was carried out using IR pyrometer. Cooling rates (i.e. solidification and solid) were calculated from the thermo-profiles of weld pool, and it increases with the decrease in heat input. From the optical images, it is observed that columnar grains originated from the fusion zone walls and merged at the center. Since, solidification front velocity is comparable on both sides’ leads to a central edge. Ferrite phase content observed in fusion zone microstructure, increases with the increase in solid cooling rate. The result suggests that the joints fabricated at lowest heat input displayed highest tensile strength. The maximum tensile strength been reported to be 872.5 ± 10.8 MPa, and failure occurred at parent metal. Tensile strength of weld joints of DSS 2205 was found to have improved with increasing cooling rate. Higher cooling rate results in the formation of fine dendritic grains as well as higher ferrite content in the weld metal.

Electron beam welding of 4J36 invar alloy to TC4 titanium alloy using Cu-Nb composite diffused metal interlayer

Electron beam welding of 4J36 invar alloy and TC4 titanium alloy was carried out with Cu-Nb composite diffused metal interlayer. The results showed that the depth to width ratio and the tensile strength of welded joints increased with the increase of electron beam current. Under the designed process parameters, two melting zones (MZ) in welded joints formed solid solutions (ss), the welded joint tensile strength reached maximum value of 244.1 MPa, and the fracture location was mainly located at 4J36/Cu interface.

Prediction of the tensile strength of friction stir welded joints based on one-dimensional convolutional neural network

Friction stir welding (FSW) is a complex thermo-mechanical coupling process. Tensile strength is an important evaluation index of the mechanical properties of welded joints. How to realize the real-time prediction of tensile strength of the friction stir welded joints to reflect the dynamic change of welding state is a problem in the field. To solve this problem, this paper presents a multi-scale one-dimensional convolutional neural network (Multi-scale 1D CNN) prediction model using time series data of temperature and axial force as inputs to realize the online prediction of tensile strength of welded joints. Firstly, FSW experiments are carried out to obtain time series data of temperature and axial force. Tensile strength values of the welded joints is obtained by tensile tests. The time series data and tensile strength values are fused as a dataset. Then Multi-scale 1D CNN, traditional 1D CNN and Multi-channel 1D CNN prediction models are established and trained with the dataset, respectively. Finally, by comparing the prediction performance of the three models, Multi-scale 1D CNN is proved to be more suitable for analyzing time series data to feedback the dynamic change of tensile strength of the joints during welding.

Taguchi optimization on friction stir welding of nitinol composite

The alumina welded joints with high quality is fabricated through friction stir welding. Through this experimental investigation, the friction stir welding were made between alumina and carbide based nitinol composite. The boron and titanium carbide based nitinol composite were fabricated through microwave sintering process. The tensile strength of welded joints was estimated and optimized through Taguchi approach. The substance properties of welded joint were evaluated. The interfacial layer formation and morphology of welded joint were investigated through scanning electron microscopy. The analysis of variance was provided the contribution of the friction stir welding factors. The objective of the research work is to enhance the welding strength using different input constrains and their level.

Optimization of parameters in rotary friction welding process of dissimilar austenitic and ferritic stainless steel using finite element analysis

Solid state joining techniques are increasingly used in joining different types of materials, in this work TP347HFG austenitic stainless steel will be welded with HiPerFer ferritic stainless-steel alloy due to their similarity in their properties to some extent after making heat treatment to ferritic alloy in addition to difference in their cost which save for economic reasons. In this work, a three-dimensional finite element model was developed. The thermal analysis and profiles between process parameters were predicted by using an ANSYS software tool. Design of experiments by Anova was used to examinate the simulation results and to evaluate contribution ratio of each parameter on responses, while grey relational analysis was used to specify the optimum trial. It was observed that trial 11 give best results (A4B2C1D1) which got higher grey relational grade. It was concluded that the friction pressure and friction time have more impact on interface temperature, whereas forging pressure and friction time affect the equivalent Von-Mises stress directly. The speed and forging pressure have a more influence on total deformation. It was also concluded that the temperature was fade out by diverging toward the end of specimen and the amount of decrease in temperature is less in ferritic side. The amount of flash extruded from both steels are approximately similar due to similarity in properties as heat treatment of ferritic alloy had been achieved. The investigation results show that trial 8 achieved highest Von-Mises stress (300 MPa) while trial 7 induced lower stress (255 MPa), maximum deformation was found equivalent to 0.012 mm with trial 16 whereas, it was found (0.008 mm) with trial 11 which were both less than the allowable deformation in end application. Tensile strength of weld joint was found equivalent to 80% of softer base metal. The hardness of optimum trial was equivalent to 156 HB.

Effect of Process Parameters on the Formability, Microstructure, and Mechanical Properties of Laser-Arc Hybrid Welding of Q355B Steel.

Thick plate steel structure is widely used in the construction machinery, pressure vessels, ships, and other manufacturing fields. To obtain an acceptable welding quality and efficiency, thick plate steel is always joined by laser-arc hybrid welding technology. In this paper, Q355B steel with a thickness of 20 mm was taken as the research object, and the process of narrow-groove laser-arc hybrid welding was studied. The results showed that the laser-arc hybrid welding method could realize one-backing and two-filling welding with the single-groove angles of 8-12°. At different plate gaps of 0.5 mm, 1.0 mm, and 1.5 mm, the shapes of weld seams were satisfied with no undercut, blowhole, or other defects. The average tensile strength of welded joints was 486~493 MPa, and the fracture position was in the base metal area. Due to the high cooling rate, a large amount of lath martensite formed in heat-affected zone (HAZ) and this zone exhibited higher hardness values. The impact roughness of the welded joint was almost 66-74 J, with different groove angles.

Influence of Heat Input on Microstructure and Mechanical Properties of Laser Welding GH4169 Bolt Assembly—Numerical and Experimental Analysis

By conducting the numerical and experimental analysis, the influence of heat input on the microstructures and mechanical properties of laser welding GH4169 bolt assembly is systematically investigated. The weld formation, temperature field, and residual stress distribution during laser welding by using the finite element modeling are consistent with experimental results. The numerical simulation results show that the increase of heat input imparts lower residual stresses and higher temperature gradient. During the process of laser welding, the steepest temperature gradient and the peak residual stress arise in the fusion zone (FZ). In addition, the dissolution of γ″ and γ′ toward the fusion line increases in heat affected zone (HAZ), but only Laves phase is observed in FZ. With increasing heat input from 24 to 48 J mm−1, the ultimate tensile strength of welded joints decreases. Both the lowest microhardness values and tensile failure of GH4169 alloy laser welded joint are in FZ. Herein, it is that the relationship among the heat input, microstructures, and mechanical properties of GH4196 bolt assembly in laser welding is systematically established, which will be of guiding significance for the selection of welding parameters in aerospace.

Microstructure evolution and deformation behavior of TIG welded 7075-T6 aluminum alloy followed by partial hot rolling

Welded joints of 7075-T6 aluminum alloys had poor formability in comparison to the base metal (BM) due to softening behavior and a performance gradient. A partial hot rolling (PHR) process was proposed in this study to improve the formability, in which only the excess weld bead region of the joints was rolled as thick as the substrate. The mechanical properties of the joints were significantly improved by subsequent heat treatment processes. The results showed that the PHR process improved the inhomogeneity of the microstructure and mechanical properties of FZ, HAZ and BM, thereby leading to a 2.3 and 1.43-fold increase in the Erichsen cupping value of hybrid joints, in comparison to welded joints and BM, respectively. Moreover, the thermomechanical treatment process increased the tensile strength of welded joints from 57.5 % to 81.7 % of the BM. The strength of thermomechanically treated joints is higher than that of joints solely with post-weld heat treatment, which is 70.6 % of the BM. This improvement in strength is linked to alterations in the microstructure and the sequence of precipitation of strengthening phases.

Friction stir welding of polypropylene based graphene nanocomposites fabricated with 3-D printing: An investigation on the microstructure and mechanical properties

Polymer nanocomposites find diverse applications in the aerospace, automobile and electronic industries due to good corrosion resistance, high specific strength and excellent processing ability. However, the production of complex and larger parts typically requires welding technology. In this research, fused filament fabrication technique was used to prepare polypropylene nanocomposite reinforced with graphene nanoplates. The polypropylene/graphene nanocomposites were then joined using the friction stir welding. Afterward, different analyses such as thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, tensile testing and hardness testing were applied to examine the effects of the process parameters on the microstructure and mechanical properties of the nanocomposite. The results of thermal analysis indicated that the addition of graphene nanoplates improved the melting point and crystallinity percentage of the polypropylene nanocomposite. Mechanical characterization of the welded samples indicated that the increase of rotational speed from 500 to 750 rpm enhanced the tensile strength of weld joint, while it reduced the hardness. Moreover, an increase in the welding speed from 10 to 30 mm/min resulted in a reduction in the tensile strength and an improvement in the hardness. The highest tensile strength of the weld was obtained by addition of 1 wt% graphene to polypropylene, whereas the hardness of the weld was maximized by addition of 2 wt% graphene. Nevertheless, the desirable combination of the process parameters for simultaneous enhancement of tensile strength and hardness was achieved by rotational speed of 667 rpm, welding speed of 16 mm/min and graphene content of 1.5 wt%.

Performance of ANN in predicting the depth to width ratio and tensile strength of UNS S32750 laser weld joints

The effectiveness of the pulsed mode laser weld joint is characterized by the supply of optical energy to the interface. The laser welding process parameters, such as laser power, pulse duration, travel speed and focus, determine the efficacy of the weld, which is defined by full penetration and free of pores and defects. However, expressing the relationship between various process parameters and mechanical strength is intricate due to the prevalence of non-linear relationship. The development of computational approaches aids in optimizing the laser welding parameters and reducing trial and error. Hence, the artificial neural network (ANN) model is developed, in a python environment, to predict the optimum process parameter values for a desirable depth to width ratio and maximum tensile strength of UNS S32750 laser butt weld joints. The developed model was assessed by experiments, not utilized for training. The ANN model predicts the depth to width ratio and tensile strength of the weld joints with an accuracy of 90% and less than 10% divergence from the experimental result. Furthermore, for the process, parametric conditions are: (power: 550 W, focus: –1 mm, pulse duration: 13 Hz and travel speed: 136 mm/min) to attain maximum tensile strength.

Mechanical properties and corrosion behaviour of duplex stainless steel weldment using novel electrodes

Mechanical and corrosion properties of welded duplex stainless steel (DSS) structures are of paramount consideration in many engineering applications. The current research investigates the mechanical properties and corrosion integrity of duplex stainless-steel weldment in a simulated 3.5% NaCl environment using specially developed novel electrodes without the addition of alloying elements to the flux samples. Two different types of fluxes having basicity indexes of 2.40 and 0.40 were used to coat E1 and E2 electrodes respectively for DSS plate welding. The thermal stability of the formulated flux was evaluated using thermogravimetric analysis. The chemical composition, using optical emission spectroscopy, and the mechanical and corrosion properties of the welded joints were evaluated as per different ASTM standards. X-ray diffraction was used to find out the phases present in the DSS welded joints while a scanning electron equipped with EDS was used for microstructural examination of the weldments. The ultimate tensile strength of welded joints made using the E1 electrode was in the range of 715–732 MPa and that of the E2 electrode was found to be 606–687 MPa. The hardness was increased with increased welding current from 90 to 110 A. The welded joint with E1 electrode coated with basic flux has better mechanical properties. The steel structure in 3.5% NaCl environment possesses substantial resistance to corrosion attack. This validates the performance of the welded joints made by the newly developed electrode. The results are discussed on the basis of the depletion of alloying elements such as Cr and Mo observed from the weldments with the coated electrodes E1 and E2 as well as precipitation of the Cr2N in the welded joints made by E1 and E2 electrodes.

Laser Oscillating of Nickel Alloyed Welds on Press-Hardened Steel

Laser oscillating welding was employed to fabricate Al-Si coated press-hardened steel (PHS) to improve the element homogeneity in the fusion zone. Laser oscillating welding was employed with various oscillation amplitudes (0 mm, 0.5 mm and 1.3 mm) in this present. Ni foil of 0.06 mm thickness was used as an interlayer between two tailored PHS welded. The weld morphology, elemental profile, microstructure and tensile strength of welded joints were studied. The results showed that full penetration weld without any weld defects were achieved for any oscillation amplitudes, and weld width increased with increasing oscillation amplitudes. With the oscillation amplitudes increased, Ni and Al had an uneven elemental profile due to strong stirring force, but the Ni and Al content in the weld was decreased and Ni had a sharp descent compared to Al element. Only few δ-ferrite was presented in fusion line with the oscillation amplitudes increased to 1.3 mm. The oscillation amplitudes did not have an effect on the tensile properties, which was similar to that of base metal. But if keeping increasing the oscillation amplitudes or reducing the thickness of Ni interlayer, it has a potential risk to form more and more δ ferrite such that deteriorate the mechnical properties of welded joints.

Characterization of Heterogeneous Microstructure and Mechanical Properties of Q345R Welded Joints including Roles of the Welding Process

In this paper, the roles of the welding process on the heterogeneous microstructure and mechanical properties of Q345R welded joints were analyzed by a series of tests, including the preparation of welded joints with different welding processes, optical microscope observation, uniaxial tensile tests, and hardness and impact measurements. The experimental results show that with the increase in welding heat input, the content of pre-eutectoid ferrite and the size of the Weidner structure increased, while the hardness and the impact absorption energy of the weld zone decreased gradually. With the increase in heat input, the volume proportion of eutectoid ferrite in the weld increased from 9.90% to 18.78%; the volume proportion of acicular ferrite decreased from 85.10% to 76.21%. With the decrease in heat input, the volume proportion of eutectoid ferrite decreased from 10.58% to 1.45%, and the volume proportion of acicular ferrite increased from 84.21% to 92.74%. Under the influence of the second welding heat, the first weld zone, the fusion zone and part of the heat-affected zone were re-austenitizing, and the distribution of ferrite and pearlite was more uniform. The hardness value of the former weld was lower than that of the second weld, and the distribution was more uniform. The maximum hardness value of the second weld zone and its corresponding heat-affected zone increased with the increase in depth. The distribution of the yield strength and the tensile strength of welded joints was similar to that of hardness.

Microstructure and mechanical properties of spray formed 7055 aluminum alloy by fiber laser-arc hybrid welding

The spray formed 7055 aluminum alloy with 4.2mm thickness was welded by laser-arc hybrid heat source. The microstructures and properties of the welded joints are studied. The results show that the weld appearance is very full and the weld zone is primary composed of equiaxed crystals. Those equiaxed crystals morphology in different positions are also different, and only a small amount of columnar crystals are locally formed in the fusion zone. The average microhardness values of the weld zone and the heat affected zone are lower than that of the base metal, reaching 64% and 82% respectively. The average tensile strength of welded joints with as-welded state reaches 51% of the base metal. However, the tensile properties of the joints are significantly improved after the two-stage solution and aging heat treatment, and the average tensile strength can reach 515MPa, which was about 84% of the strength of the base metal.

Effect of process parameters on performances of TWIP steel/Al alloy dissimilar metals butt joints by laser offset welding

In this paper, butt joints of twinning-induced plasticity (TWIP) steel and aluminum alloy dissimilar metals were carried out by the laser offset welding method, and the amount of the aluminum alloy that melted was controlled by adjusting the offset distance of the laser beam spot. The aim of this study was to regulate the influence of the intermetallic compounds (IMCs) layer thickness, crystal structure and crack defects on the tensile strength of the welded joint. The tensile strength of the welded joint was obviously improved by adjusting the welding process parameters without adding any alloying elements. The results demonstrated that the crack initiated at the junction between the aluminum base metal and the weld seam and propagated along with the interface. The increase in the recrystallized fraction was beneficial to improve the tensile strength of the joint. The tensile strength of welded joints with more low-angle grain boundaries was lower. The smaller the thickness of the IMCs layer was, the higher the welded joint strength was. The optimized welding process parameters were as follows: d = 0.2 mm, P = 900 W, V = 15 mm/s and △f = −2 mm in the present study, and the tensile strength of the joint reached 155 MPa. This study provides a theoretical basis for solving the welding cracking problem of steel/aluminum heterojunctions without additional interlayer material and so as to improve the strength of the steel/aluminum laser welded joint.

Potential use of Friction Welding for Fabricating Semi-Biodegradable Bone Screws

Certain surgical interventions, such as fractures, may require implants that have a combination of external and internal parts made of inert and biodegradable biomaterials, respectively. This implant design can be fabricated using specific fabrication methods such as friction welding that are able to efficiently combine two biomaterials. This study reports the utilization of the direct friction welding technique for the fabrication of semi-biodegradable bone screws using two parent metals of low carbon steel and austenitic stainless steel 202. The welding parameters were optimized to obtain welded joints for bone screw fabrication. The mechanical properties of metals that have been welded were identified through tensile and three-point bending analyses. The corrosion test was then conducted on the welded metals through the measurement of corrosion rate, changes in pH value, morphology visualization, and element release, while the cytotoxicity effect was evaluated through a cell viability test. Screw implant materials with a diameter of up to 12.7 mm were successfully fabricated using a continuous friction drive welding machine at 4000 rpm and 24.5 MPa hydraulic pressure. The results of mechanical testing show that the tensile strength of weld joints decreased by 3.6% from low carbon steel and 20.4% from stainless steel. Fractures were observed at the welding interface after being subjected to flexural testing. The pH value of the Saline solution decreased from 7.13±0.06 to 6.73±0.06 after the welded metals were immersed for up to 8 weeks. Evaluation of the surface morphology in all welding zones at week eight samples obtained that almost all types of corrosion that occurred were uniform corrosion, except in the PZ zone where galvanic corrosion was formed. The concentrations of Cr and Ni ions (ppm level) were very low, namely 0.058 ppm for Cr and 0.199 ppm for Ni. The viability of human fibroblast cells was maintained at higher than 75% viability after the cell incubation at 1, 3, and 5 days with different parts of welded joints.

Microstructure and mechanical properties of 2A12 aluminum alloy welded joint through CMT double side welding

In this work, the cold metal transfer (CMT) double side welding was carried out to weld 2A12 aluminum alloy plate. The influence of the heat input on the weld appearance was studied, which indicated that when the heat input was exceeded to 651.75 J/mm the better weld appearance was obtained. Through the scanning electron microscope (SEM), electron back-scatter diffraction (EBSD) and tensile testing, the microstructure and mechanical properties of welded joints were investigated. The results showed that the size of microstructure in the front weld seam was less than that of the back weld seam due to the secondary thermal cycle. With the increases of heat input, the average grain size and elongation of welded joints were increased, the tensile strength of welded joints was reduced. The strength coefficient of welded joint was about 70%. The fracture model of welded joint belonged to ductile fracture.

Effect of shielding gas on microstructure and mechanical properties in AA6061-T6 alloy MIG welding

Due to its properties such as high strength/weight ratio, enhanced corrosion resistance, low density, AA6061-T6 aluminum alloy welding is widely used in structural, automotive and rail industry. In this study, AA6061-T6 alloy was welded with robotic metal inert gas technique using ER5356 filler wire. The effects of different shielding gas composition ratios (argon/helyum) on the macro / microstructre, mechanical properties (hardness, tensile strength) of the weld joint were investigated. Welding porosity decreased with the addition of helium gas to argon gas. Accordingly, the tensile strength of welded joints increased from 190 MPa to 221 MPa with the addition of helium gas. The strength of the welded joints (190-221 MPa) was obtained lower than that of the base material (290 MPa) due to the changes in the microstructure as a result of the weld thermal cycle and grain coarsening in the heat affected zone. Dentritic, columnar and coarse shaped grains were observed along the weld section, respectively in the weld bead, partially melted zone and heat affected zone. The differentiation of the shielding gas composition did not cause these regions to change, but the heat affected zone expanded with the increase in the helium content. The change in hardness of the cross section of welded joint has increased from around 60 HV to 90 HV from the welding area to the base material. 25% Argon-75% Helium gas mixtures provided optimum combination in terms of microstructure, mechanical properties and cost.

Mechanical characterization and simulation of PCGTAW welded thin sheet of SDSS material

In this research paper, Pulsed Current Gas Tungsten Arc Welding (PCGTAW) process is used to weld the thin sheet of Super Duplex Stainless Steel (SDSS). From the Bead on Plate (BoP) trials the parameters for full penetration butt joint were identified. Heat input obtained from the welding parameter is 0.144 kJ/mm. Microstructural characterization of Welded joint revealed the coarse grain microstructure in the Heat Affected Zone (HAZ) and Weld Zone (WZ) due to weld thermal cycle and slows cooling rate concern. Due to this high temperature in the WZ austenite grains are changed in the shape of Widmanstatten austenite, grain boundary austenite, and intragranular precipitates created from ferrite grains. The tensile strength of welded joints (800Mpa) is 3.75% less as compared to base metal tensile strength (830Mpa). The ductility of the weld joint is decreased as compared to base metal due to the presence of coarse grain in the HAZ and WZ. PCGTAW joint's micro-hardness is 0.7 HRC lower than the base metal due to weld thermal cycle involvement. Abaqus software is used to validate the tensile test result. The numerical analysis result is similar to the experimentally obtained tensile test result with a maximum error percentage is of 0.8%.