Welding Of Alloys Research Articles

Titanium Alloy Weld Time-of-Flight Diffraction Image Denoising Based on a Wavelet Feature Fusion Deep-Learning Model

Titanium Alloy Weld Time-of-Flight Diffraction Image Denoising Based on a Wavelet Feature Fusion Deep-Learning Model

Multi-response Optimization of GTAW Process Parameters in Terms of Energy Efficiency and Quality

This work optimizes the current (I), voltage (V), flow rate (F), and arc gap (G) of the gas tungsten arc welding (GTAW) of the Ti40A titanium alloy to decrease the heat input (HI) and improve the ultimate tensile strength (TS) and micro-hardness (MH). The radial basis function network (RBFN) was utilized to present performance measures, while weighted principal component analysis (WPCA) and an adaptive non-dominated sorting genetic algorithm II (ANSGA-II) were applied to estimate the weights and generate optimal points. The evaluation via an area-based method of ranking (EAMR) was employed to determine the best solution. The results indicated that the optimal I, V, F, and G are 89 A, 23 V, 20 L/min, and 1.5 mm, respectively. The improvements in the TS and MH were 1.2 % and 19.8 %, respectively, while the HI was saved by 18.4 %. The RBFN models provided acceptable accuracy for prediction purposes. The ANSGA-II provides better optimality than the conventional NSGA-II. The HI, TS, and MH of the practical GTAW Ti40A could be enhanced using optimality. The optimization method could be utilized to deal with optimization problems for not only other GTAW operations but also other machining processes.

FEM-Based Conductive Heat Transfer Analytical Description of Solidification Rate and Temperature Gradient during Lateral Laser Beam Oscillation Welding of Aluminum Alloy.

This study investigates the feasibility of utilizing the finite element method (FEM)-based conductive heat transfer (CHT) analysis simulation to determine temperature gradients and solidification rates at the solid-liquid interface during laser beam oscillation welding. By comparing experimental observations with FEM-based CHT analysis, the underlying microstructural evolution and grain formation during welding were examined. FEM-based CHT enables the calculation of temperature gradients (G) and solidification rates (R), offering insights into the formation of equiaxed structures, which are crucial for suppressing hot cracking. Columnar-to-equiaxed structure transition thresholds, such as G/R and G3/R, accurately predict the emergence of fully equiaxed grain structures, validated by electron backscatter diffraction. This research provides valuable insights into temperature gradients and solidification rates in oscillation welding, guiding process design for achieving refined equiaxed structures and minimizing hot cracks.

Effect of Quenching and Aging on the Microstructure and Mechanical Properties of Welded Joints Obtained by Laser Welding of Titanium and Aluminum Alloys

Effect of Quenching and Aging on the Microstructure and Mechanical Properties of Welded Joints Obtained by Laser Welding of Titanium and Aluminum Alloys

Experimental investigation of friction stir welding with special spherical ball shoulder different probe tools and parameters for enhanced material properties of AA2219 aluminium alloy

This research investigates the impact of unique spherical ball shoulder enhancement tool pin configurations on the friction stir welding (FSW) of AA2219 aluminum alloy under various parameters. FSW was performed using three different pin shapes: square, hexagonal, and octagonal. Testing samples were prepared using an L9 orthogonal array layout with varying welding parameters. The material behavior in the three distinct weld zones was evaluated for each pin configuration. Results indicated superior microhardness values in the heat-affected zone (HAZ) and thermo-mechanically affected zone (TMAZ) compared to the weld nugget zone. Elemental composition analysis of the TMAZ revealed significant differences, highlighting the influence of thermal stress and material behavior due to the tool pin and shoulder configuration. The square-headed tool demonstrated improved tensile strength and microhardness. Optimal welding performance was achieved with a spindle speed of 1000 RPM, a travel speed of 25 mm/min, and a tilt angle of 3°. Variations in Cu content in the TMAZ and HAZ underscored localized modifications within the material structure, driven by the spherical ball spinning effects on the shoulder. Tensile tests showed that welds made with the square pin consistently exhibited higher tensile strength compared to those made with hexagonal and octagonal pins.

Numerical simulation and experimental investigation on friction stir welding of AZ31 magnesium alloy

Integrated numerical simulations and experimental investigations were employed to scrutinize the thermal, mechanical, and microstructural transformations of the AZ31 magnesium alloy during the friction stir welding (FSW) process. Especially, the primary focus was on the influence of process parameters such as rotational speed and welding speed on the temperature distribution, grain refinement, and mechanical properties of welded joints in alloys. By employing Deform-3D coupled with the integration of constitutive equations and dynamic recrystallization (DRX) models, the FSW process was investigated. The investigation revealed a significant increase in temperature when the tool’s shoulder made contact with the weld, resulting in the substantial accumulation of heat during FSW. Distinctions became apparent between the advancing side (AS) and the receding side (RS), with the AS exhibiting slightly elevated levels of temperature, equivalent stress, strain, and grain size. Specifically, adjustments in the rotational speed of the stirring tool and a reduction in welding speed resulted in larger grain sizes within the alloy. For example, when the rotational speed was set at 1200 rpm and the travel rate was 200 mm min−1, the initial grain size of the weld experienced a substantial decrease from 57.8 μm to 8.2 μm. Subsequent experimental verification, considering grain size and microhardness, was carried out to optimize FSW parameters for achieving the desired material properties. The accuracy of simulation results was validated through a meticulous comparison with experimental findings, underscoring the potential of numerical simulation in comprehending and predicting FSW processes.

CFD modeling for predicting imperfections in laser welding and additive manufacturing of aluminum alloys

Aluminum and its alloys are widely used in various applications including e-mobility applications due to their lightweight nature, high corrosion resistance, good electrical conductivity, and excellent processability such as extrusion and forming. However, aluminum and its alloys are difficult to process with a laser beam due to their high thermal conductivity and reflectivity. In this article, the two most used laser processes, i.e., laser welding and laser powder bed fusion (LPBF) additive manufacturing, for processing of aluminum have been studied. There are many common laser-material interaction mechanisms and challenges between the two processes. Deep keyhole mode is a preferred method for welding due to improved productivity, while a heat conduction mode is preferred in LPBF aiming for zero-defect parts. In LPBF, the processing maps are highly desirable to be constructed, which shows the transition zone. Presented numerical modeling provides a more in-depth understanding of porosity formation, and different laser beam movement paths have been tested including circular oscillation paths. High accuracy processing maps can be constructed for LPBF that allows us to minimize tedious and time-consuming experiments. As a result, a modeling framework is a highly viable option for the cost-efficient optimization of process parameters.

Interfacial microstructure characteristics and failure mechanism of the laser welding-brazing steel-Al joints with various welding parameters

The microstructure details of the interface, mechanical properties and failure mechanism of laser welding-brazing (LWB) steel-Al joints with various welding parameters were comparatively investigated. The emergence of ternary Fe–Al–Si intermetallic compounds (IMCs) was observed in the interfacial area of the joints prepared utilizing ER4047 filler. In contrast, only the binary Fe–Al IMCs were formed in the interfacial area of the joints prepared employing ER5356 filler. With the same laser tilt angle, the IMCs layer of the joints prepared with ER4047 was thinner than that of the joints prepared with ER5356, implying the rapid growth of the IMCs welded via the ER5356 filler. The tensile strength exhibited by the former surpassed that of the latter. Employing the same filler metal, the average thickness of the IMCs layer of the joints with laser tilt angle of 10° was smaller than that of the joints with laser tilt angle of 20°. The strength of the joints with smaller tilt angle was better than that of the ones with bigger tilt angle. The tensile test outcomes revealed that there existed failure competition among the Al alloy base metal (Al-BM), weld metal (WM) and interface structure. If the interface structure was Fe–Al IMC with high brittleness, the cracks propagated along the interface, and finally fractured at the interface. If the interface structure was Fe–Al–Si IMC with good toughness, the crack propagation in the interface region could be hampered. In this case, the joint was prone to occur via WM failure or even Al-BM failure modes.

A Novel Technique for Improving Cyclic Behavior of Steel Connections Equipped with Smart Memory Alloys.

Residual drifts are an important measure of post-earthquake functionality in bridges and buildings, and can determine whether the structure remains fit for its intended purpose or not. This study aims at investigating numerically, through finite element (FE) analysis in ABAQUS, the cyclic response of exterior steel I beam-hollow column connection using welded shape memory alloys (SMA) bolts and seat angles. This is followed by validating the numerical model using an accredited experimental data available in the literature through different techniques, (1) SMA bolts, (2) SMA angles, (3) SMA bolts and angles. The parameters investigated included: SMA type, SMA angle thickness, SMA bolt diameter, SMA angle stiffener and SMA angle direction. The cyclic performance of the steel connection was enhanced further by varying the bolt diameter, plate thickness, angle type and direction. The results revealed that the connections equipped with a combination of SMA plates and SMA angles reduced the residual drift by up to 94%, and doubled the self-centering capability compared to conventional steel connections. Moreover, the parametric analysis showed that Fe-based SMA members could be a good alternative to NiTi based SMA members for improving the self-centering capability and reducing the residual drifts of conventional steel connections.

Experimental and numerical research on formation mechanism of intermetallic compounds in laser brazing welding for Ti/Al dissimilar alloy

Laser brazing is an esteemed technique for Ti/Al dissimilar alloy welding, yet the emergence of brittle intermetallic compounds (IMCs) restricts its broader application. In-depth knowledge of IMCs formation provides critical insights for process optimization targeting IMCs structural improvement, pivotal to high-performance of Ti/Al joint. Herein, we establish macroscopic heat transfer-fluid flow coupled model for laser brazing welding of Ti/Al dissimilar alloys firstly, followed by a comprehensive characterization of the types, distribution, and crystallographic features of IMCs, thereby elucidating the impact mechanism of laser offset on IMCs growth. Incremented laser offset prompts a conversion from transverse to tangential flow at the Ti/Al interface, attenuates peak temperatures and liquid phase duration, and significantly revises solidification parameters, thereby reducing the IMCs layer to 5 μm, augmenting solid-state transformation characteristic, and diversifying crystallographic orientations of IMCs. Ultimately, enhanced tensile strength in the Ti/Al joint is attributed to the presence of thinner IMCs with finer grains, produced by larger laser offset. This article constitutes a pivotal progression in modeling heat transfer-flow behaviors for Ti/Al laser brazing welding, revealing IMCs genesis with unparalleled granularity guided by crystal selective growth principles. It also lays a theoretical foundation for IMCs micro-structure improvement strategy via temperature-flow regulation.

Weldability Study and Improvement in Weld Strength of Aluminium Alloy

This paper explores the weldability of 6063 T6 Aluminium Alloy using Response Surface Methodology (RSM) as the Design of Experiment. The study aims to investigate the influence of various welding parameters like Peak Current and Pulse-on-time on the quality of welds on the aluminium alloy and optimize these parameters to achieve desirable weld characteristics. The research utilizes RSM to develop mathematical models that can predict the weld quality based on the welding parameters. The findings of this study can contribute to enhancing the understanding of aluminium alloy weldability and provide insights for optimizing welding processes in industrial applications.

Modeling and validation of hydrogen porosity formation in aluminum laser welding

Laser welding is used to weld aluminum alloy 1100 for battery cell manufacturing in the automotive industry. However, these welds can have porosity that can decrease their performance in the battery packs. One type of porosity is gas porosity, commonly understood to be due to hydrogen entrapment in the weld during solidification. Hydrogen is dissolved in the molten aluminum at elevated temperatures during laser heating and can be entrapped in the weld pool upon solidification. When welding anodized aluminum, the amount of hydrogen porosity is increased because the anodized oxide layer is broken up and the broken-up oxide can act as heterogeneous nucleation sites for hydrogen pores. A cellular automaton model has been developed to predict the nucleation and growth of hydrogen porosity during laser welding. This model has been validated with microstructure analysis, LECO® hydrogen analysis, and X-ray micro-computed tomography. This model can be used by welding engineers to reduce porosity and control weld quality during laser welding of aluminum alloys.

Mechanical response and microstructural evolution of a composite joint fabricated by green laser dissimilar welding of VCoNi medium entropy alloy and 17-4PH stainless steel

In engineering structures, the application of advanced alloys, such as the VCoNi medium-entropy alloy (VCoNi-MEA), with remarkable tensile strength (> 1 GPa) and superior ductility necessitates the employment of dissimilar joints. This study pioneers the dissimilar joining of VCoNi-MEA and 17–4 precipitation hardening stainless steel (17–4PH STS) using state-of-the-art green laser beam welding (LBW). To evaluate and optimize the experimental parameters, two welding speeds (200 and 300 mm/s) along with post-weld heat treatment (PWHT) were incorporated. High-quality welded joints with a single-phase face-centered cubic (FCC) structure in the fusion zone (FZ), minimal precipitates (< 1.6 %), and no visible cracks were successfully created. The LBW process demonstrated effective low-heat input characteristics, evident from a considerably narrow heat-affected zone (HAZ). Control over FZ width and grain size was achieved, measuring 600 and 112 μm at low welding speed and 250 and 49 μm at high welding speed, respectively, significantly lower than previous studies. A remarkably high yield strength (YS) of ∼620 MPa and ultimate tensile strength (UTS) up to 845 MPa were observed in the as-welded conditions, improving to ∼645 and 875 MPa, respectively, after PWHT. This enhancement in mechanical properties is primarily attributed to lattice friction induced by V addition. PWHT also improved joint ductility, increasing from 3.5 % to 8.6 % (low-speed) and from 6.3 % to 9.2 % (high-speed). The reduction in crystallographic orientation achieved using a higher welding speed and PWHT emerged as a major reason for improved mechanical properties. Slip-based deformation mechanisms dominated across all conditions, featuring crystallographically aligned slip bands. Interactions between existing and additional slip bands formed a dense dislocation network crucial for enhanced elongation after PWHT. Thermodynamic parameters elucidating phase stability in the observed FZs and contributions to superior YS were calculated and comprehensively discussed.

Friction stir lap welding of AZ31B magnesium alloy to AISI 304 stainless steel

Abstract AZ31B magnesium alloy plates were lap-joined to AISI 304 stainless steel plates through the friction stir welding (FSW) method and utilizing various tool welding speeds. It has been found that the most important factor governing the weld strength is the hook formed on the advancing side of the welds. The weld tensile shear strength improved with an increase in the tool feed rate. Because, in general, height, length, and width of the hook taking place on the advancing side shrunk. Furthermore, the angle between the hook and interface of the plates increased, leading to reduced sharp corner formation. Apart from these, imperfections such as cavities, voids, and uncombined regions at the weld interface reduced and disappeared when increasing the welding speed. During the tensile shear test, all the welds fractured tensile mode and brittle type from the top AZ31B plate next to the hook on the advancing side. There was no breakage occurred in the weld interface, which is an indication of the strong joints. No intermetallic compounds between iron and magnesium were determined at the fracture region. At lower welding speeds, a higher amount of AISI 304 particles occurred at the weld stir zone resulting in a higher hardness.

Improved understanding of the growth of blocky alpha in welded Zircaloy-4

Zirconium alloys are widely used in nuclear reactors as fuel cladding materials. Fuel cladding is used to contain the nuclear fuel and cladding tubes are typically sealed using welds. Welding of zirconium alloys can result in changes in the local microstructure, with the potential to grow so called ‘blocky α’ grains in the welded region during subsequent thermal processing and these blocky α grains have the potential to be detrimental to the integrity of the component. In this work, complimentary heating experiments with ex situ and in situ electron backscatter diffraction (EBSD) analysis are used to aid understanding of the blocky α grain growth within the weld region. These experiments reveal that blocky α grain growth is related to the prior-β (high temperature) microstructure, as grains grow adjacent to a prior-β grain boundary and the orientation of the growing α grain can be explained using neighbourhood orientations from this prior-β grain. This growth mechanism is explained via a simple mechanism which is related to the α grain orientations, grain boundary structures and local stored energy. Ultimately, our findings indicate that the likely grain growth (size and morphology) across the weld region can now be predicted from the initial as-welded microstructure.

Effect of process parameters on weld geometry and mechanical properties in friction stir welding of AA2024 and AA7075 alloys

FSW joints are promising because they have a minimal heat input in welding and can limit the amount of intermetallic compound formation in dissimilar metals. Solid-state welding processes, particularly friction stir welding (FSW), are preferred for welding aluminium alloys due to their low heat input and ability to minimize intermetallic compound formation. This study conducted FSW trials on AA7075 and AA2024 alloys, each 4 mm thick. Parameters such as axial force, rotational speed, and traverse feed were adjusted while keeping other factors constant. The study analyzed weld geometry characteristics, including bead width and penetration depth. Angle distortions during FSW of thin plates in a butt joint were investigated. Additionally, the study examined the effects of FSW parameters on mechanical properties such as tensile strength and hardness immediately after welding. Microstructures of the welds were observed using optical microscopy (OM). The optimal mechanical properties are achieved at a rotational speed of 1000 rpm, a traverse feed of 30 mm/min, and an axial force of 10 kN. This optimal condition facilitates material flow around the pin at an ideal speed, ensuring adequate material filling and preventing tunnel formation. The stir zone's microstructure under these parameters exhibits a finely recrystallized structure with a significantly smaller grain size than the base material. Consequently, this enhances the joint's microhardness and tensile strength.

Influence of solid-state laser radiation on the process of pulsed-arc welding of aluminium alloy 1561

Influence of solid-state laser radiation on the process of pulsed-arc welding of aluminium alloy 1561

Microstructure and mechanical properties in VPPA keyhole welding of thick aluminum alloy

In this study, the 16 mm thick aluminum alloy was successfully welded using variable polarity plasma arc (VPPA) keyhole welding. The microstructure and microhardness distributions of the weld were systematically measured along its thickness and width. To evaluate tensile strengths along the weld thickness, tensile specimens were divided into upper, middle, and lower sections. The surface temperature distribution of the weld pool, along with the temperature profile through its thickness, was measured using thermometers and thermocouples. Numerical simulations were employed to calculate the pressure oscillations along the keyhole boundary and to analyze the temperature and flow field distributions of the VPPA. The findings initially revealed a homogeneous and refined microstructure distribution within the weld seam. The weld zone exhibited higher microhardness compared to the base metal (BM). The weld demonstrated a tensile strength of 187.86 MPa and an elongation of 24.76%, corresponding to 95.57% and 78.65% of the BM, respectively. The tensile strengths and elongations of the upper, middle, and lower sections displayed a similar distribution to that of the entire weld. The mechanism underlying the microstructure distribution of the weld was significantly influenced by the temperature distribution of the weld pool, dynamic pressure oscillations in the mushy zone, and fluid flow of the weld pool. Specifically, the mechanism whereby pressure oscillations fracture existing nuclei and generate multiple new nuclei has been proposed to explain the refined microstructure distribution. These findings provide crucial insights for optimizing VPPA keyhole welding technology, ensuring stable and high-quality welding of thick aluminum alloys.

Effect of laser power on weld microstructure of AA6082 sheets remote laser welded by circular beam wobbling

This paper aims to investigate the combined effect of circular beam wobbling and varying laser power on crack formation, weld geometry, microstructure and hardness during remote laser welding of AA6082 alloy. AA6082 sheets of 2 mm thickness were joined in overlap weld configuration using wobbling mode remote laser welding at 4 kW, 3 kW and 2.5 kW. Full penetration was achieved in the joints made at 4 kW and 3 kW, with severe crack formation. Welds at 2.5 kW showed partial penetration and no cracks; however, porosity formation was observed. While no significant change was observed in the dendritic structure and compound contents in fusion zones with full penetration, compound clusters dominated by Cu and Si elements were revealed in the seam root region at 2.5 kW (partial penetration). In full penetration welds (4 and 3 kW), the hardness decreased in the center of the fusion zone but increased from the surface to the root zone. However, for the partial penetration weld (2.5 kW), a limited change in the hardness values determined in the same direction was observed.

Wet corrosion of incinerators under chloride deposits: Insights from experimental study on stainless steels and nickel-based alloy weldments

The deliquescence of the corrosion species produced by nuclear waste incineration, in particular ZnCl2, makes wet corrosion possible even in dehumidified atmosphere complicating the corrosion risk management of the equipment. A specific cyclic corrosion test was used to assess the compatibility of corrosion resistance alloys to such conditions. Thereby, AISI 316 L welds resisted somehow to pitting but experienced severe stress corrosion cracking, while UR66™ showed only pitting in the heat affected zone. Hastelloy® C22 exhibited better performance, with localized corrosion only in the fusion zone, that was greatly influenced by the composition of the filler materials and welding techniques.