This study explores the feasibility of stationary shoulder friction stir welding (SSFSW) for joining dissimilar extruded aluminum alloys, AA6082-T6 and AA6005A-T6, targeted for structural applications in the transportation industry. The key objective is to achieve higher welding speeds, up to 1.5 m/min, which is significantly higher than those typically reported for SSFSW in lap joint configurations. This increased welding speed is expected to reduce heat input, narrow the heat-affected zone (HAZ), and improve the microstructural uniformity and mechanical performance of the weld. Microstructural characterization via optical microscopy, scanning electron microscopy, and electron backscattered diffraction revealed extensive dynamic recrystallization within the stir zone, resulting in a refined average grain size of approximately 2.3 µm. Hardness mapping across the weld cross-section showed a significant reduction in hardness within the stir zone and HAZ, with the minimum hardness dropping to 65 HV from the base material hardness of 110–115 HV. High-speed SSFSW at 1.5 m/min produced sound joints with good lap interface bonding, despite the presence of a small root void. Lap shear tensile testing showed an average ultimate load of 3.8 kN, with all samples failing from the advancing side hook defect due to stress concentration. Fractographic analysis confirmed ductile failure modes with dimples in the fracture surface. These results suggest that high-speed SSFSW (1.5 m/min) is a promising technique for joining dissimilar aluminum alloys in lap joint configurations, offering potential advantages in microstructural refinement and mechanical performance compared to conventional methods. 

This study examines the application of Cold Metal Transfer Wire Arc Additive Manufacturing (CMT-WAAM) to Inconel 718. Seven shielding gas combinations were assessed by depositing multi-bead (‘snicker’) samples. The samples were characterized with respect to defect occurrence, penetration depth, bead geometry (width, height and toe angle) and arc power. The results confirm the high feasibility of using WAAM for Inconel 718. Among the tested gases, the gas mixture of 2% H2 in Ar (sample R7) exhibited no crack-like defects, minimal volumetric defects, a larger toe angle and a higher width-to-height (W/H) ratio, while maintaining reduced penetration compared to the other gas combinations. Shielding gas composition was found to significantly influence arc power at constant wire feed speed, with a strong correlation to carbon dioxide (CO2) content. Elevated arc power, in turn, was associated with increased defect formation, particularly crack-like defects. A strong correlation between toe angle and W/H ratio was also observed, both being sensitive to shielding gas composition. Moreover, shielding gas selection substantially impacted the overall geometry of the deposited structures.

A key challenge in the production of high-grade automotive aluminum components through the High-Pressure Die Casting (HPDC) process is the imperative to minimize imperfection. In addressing this concern, this study utilizes friction stir processing (FSP), a widely recognized intense plastic deformation technique. FSP is applied to systematically alter the microstructure of HPDC Al-4Mg-2Fe, a prominent alloy extensively used in the die-casting sector. By using the pass strategy to incorporate both one-pass and two-pass approaches, the microstructure is selectively altered to establish a defect-free processed zone. The utilization of FSP demonstrates its efficacy in breaking aluminum dendrites and acicular silicon particles, leading to a uniformly dispersed arrangement of equiaxed silicon particles within the aluminum-based matrix. In addition, FSP eradicates porosity and disintegrates needle-like Fe particles, resulting in a more refined and homogeneously distributed structure. Subsequently, the material’s mechanical properties processed by FSP were assessed in the longitudinal direction concerning the processing axis and then compared with those of the original base material. The microstructural refinement and reduction in porosity induced by FSP result in a notable enhancement in hardness, with an increase of 23 % after one pass and 37 % after two passes. The substantial improvement in mechanical properties during the FSP process is predominantly attributed to modifications in the morphology, refinement, and dispersion of intermetallic particles within the matrix. This improvement is further complemented by the ultrafine dispersion of casting defects. This study underscores the efficacy of FSP as a valuable tool for modifying microstructures and improving mechanical properties in HPDC Al-4Mg-2Fe alloys. Such advancements align with the lightweighting objectives pursued by the automotive industry. 

Wire Arc Additive Manufacturing (WAAM) utilizes wire as the feedstock and welding arc as the heat source. While Solid Wires (SW) are common, exploration of tubular wires such as Metal Cored Wires (MCW) in Additive Manufacturing (AM) is limited. MCW offers flexibility for alloy design, but both SW and MCW can create silicon islands on welds, affecting mechanical properties and processability. This study uses Gas Metal Arc Welding (GMAW) in Cold Metal Transferred (CMT) mode to compare SW and MCW deposits with different gases. MCW shows more uniform penetration, potentially reducing lack of fusion in AM layers. A novel approach is then used to modify the MCW to minimize silicate formation, reducing islands on the surface. Comparative analysis shows a significant reduction and change in the location of silicates with modified MCW compared to standard, with mechanical properties in as-welded and after post-weld heat treatment (PWHT) remaining comparable to the standard wire.

The graphic abstract was missing from this article and it has been given in this correction. The original article has been corrected. © 2022, The Author(s) under exclusive licence to The Korean Institute of Metals and Materials.

Continuous cooling transformation (CCT) diagrams of base metals are common in welding. They can be built using physical or numerical simulations, each with advantages and limitations. However, those are not usual for weld metal, considering its variable composition due to the dilution of the weld into the base metal. Wire Arc Additive Manufacturing (WAAM) is a distinctive casein which the interest in materials comparable with weld composition raises attention to estimating their mechanical properties. Notwithstanding, this concept is still not used in WAAM. Therefore, the aim of this work was to address a methodology to raise MC-CCT (Multiple Cycle ContinuousCooling Transformation) diagrams for WAAM by combining physical and numerical simulations. A high-strength low-alloy steel (HSLA) feedstock (a combination of a wire and a shielding gas) was used as a case study. To keep CCT as representative as possible, the typical multiple thermal cycles for additive manufacturing thin walls were determined and replicated in physical simulations (Gleeble dilatometry). The start and end transformations were determined by the differential linear variation approach for each thermal cycle. Microstructure analyses and hardness were used to characterise the product after the multiple cycles. The same CCT diagram was raised by a commercial numerical simulation package to determine the shape of the transformation curves. A range of austenitic grain sizes was scanned for the curve position matching the experimental results. Combining the experimental data and numerically simulated curves made estimating the final CCT diagram possible.

The present study focuses on developing lightweight assembly of two different aluminium alloys extruded and high pressure die cast (HPDC) for battery frame assembly in BEV. The goal is to produce defect-free welds in lap configuration with smooth surface finish. Stationary shoulder friction stir welding (SSFSW) was employed with welding speeds of 3–15 mm/s. EBSD analysis revealed two groups of grains in the stir zone (SZ) due to dynamic recrystallization. Moreover, the grain size of the SZ significantly decreased compared to both alloys. The cast alloy contains large iron particles, and that were broken by the rotating probe, and the stirred material consisted of fine dispersed precipitates. Tensile-shear test found the fracture location at the hook area near to cast, and a model representing fracture behavior is also discussed. With increasing welding speed from 3 to 5 mm/s, the tensile strength found ∼95 and ∼100 MPa, respectively without any significance difference in the fracture behavior and location. Overall, this study provides valuable insights such as materials mixing, grain refinement, and joint strength in dissimilar joining using SSFSW. The findings could be useful in developing optimized welding parameters and improving the overall quality and productivity of the SSFSW process for battery pack assembly in BEV.

Present work demonstrates high speed friction stir welding (HSFSW) of light weight battery trays assembly in electric vehicle (EV). Despite of solid-state and green nature of FSW, it suffers from the relatively low welding speed. With the help of suitable tool design and machine tool parameters, we successfully achieved defect-free welds at high welding speed of 4.0 and 4.5 m/min. Good quality welds are produced in 3 mm thick AA6063-T6 extruded aluminium alloy at such a high welding speeds by implementing violent material mixing i.e., higher tool rotation speeds (3500–4500 rpm) and plunge force (8.5–10.5 kN). The HSFSW cross-section registered curious hardness profile of ‘U’ shape. HSFSW resulted softening of weld stir zone (∼60 HV) along with HAZ (∼50 HV). The highest joint efficiency of 72 % was found for the weld produced at 4.0 m/min and 3500 rpm.

Present work aims to achieve high welding speed during friction stir welding of lightweight battery trays in the electric vehicle industry. This study reports high-speed friction stir welding (HSFSW) up to 4.0 m mi -1 in AA6063-T6 alloys. The defect-free HSFSW joints are produced by adopting aggressive material mixing, i.e. higher tool rotation and plunge force. HSFSW weld cross-section reported an unusual hardness profile of "U"shape instead of "W"shape in conventional FSW of AA6xxx alloys. HSFSW resulted softening of weld stir zone (~60HV) along with HAZ (~53HV) against the base material (BM) hardness of ~90HV. The HSFSW at 4.0 m min -1 obtained good joint strength of 71% of the BM. Microstructure evolutions across the fractured weld cross-section are discussed using EBSD analysis.

The present endeavour is to augment mechanical attributes via friction stir processing (FSP) in hypereutectic aluminium-silicon castings by the means of microstructural modifications and defects reduction. Wherein, the study proceeds with mainly two approaches namely, alteration in tool revolution (TR) and the number of FSP passes. The prepared specimens were evaluated investigating volume fraction of porosities, microstructural characterizations and microhardness. Therefrom, the specimen with highest number of passes delivered most uniform properties resulting from the reduction in casting porosities and refined silicon particle uniform distribution throughout friction stir processed zone. This endeavour may be considered as a footstep towards more industrial readied material transformation.