22MnB5 steel blanks (Usibor ® 1500) are widely used in automotive crash-resistant components because of their high strength. However, laser welding of Al–Si-coated 22MnB5 is challenging because coating dilution in the weld pool promotes soft δ-ferrite phase formation, reducing weld strength. An industrial solution is laser-ablation, while filler wire addition provides an alternative means to modify fusion-zone chemistry, with or without ablation. In this study, micro-structural development and mechanical performance of laser-welded Al-Si-coated 22MnB5 were investigated using ER4130 and ER420 filler wires. Energy-dispersive spectroscopy showed reduced bulk aluminum-(Al) content in welds with both filler wires relative to as-received welded hot-stamped welds, correlating with reduced δ-ferrite formation and increased martensite content. Higher chromium in ER420 further enhances hardenability, while carbon addition on wires further promoted martensite formation. These findings offer insights for Cr–C-based filler wire selection and advancing laser welding strategies for high-strength structural applications.

This article investigates void defect formation in friction stir welding (FSW) of AA2024, AA5052 and AA7075. A total of 159 bead-on-plate welds were performed with real-time monitoring of temperature, force and spindle power. Travel speeds from 25 to 500 mm/min and tool rotation speeds from 300 to 1500 RPM were investigated. Process maps identified critical parameter ranges for different void defects. A new method was proposed to estimate torque from spindle power. Results show that high temperatures ( > 0.7 T solidus ) are necessary but not sufficient for defect-free welds. Torque thresholds can distinguish cavity from tunnel and groove defects, while power input below 1000 W (AA2024) or 1050 W(AA7075) is generally necessary and sufficient to avoid voids. These findings enable real-time defect monitoring and process optimisation in FSW.

Friction stir welding (FSW) is widely used for joining lightweight automotive and aerospace materials such as AlSi10Mg, but the process often produces softened weld zones that limit joint performance. This study demonstrates that employing a Cu interlayer together with post-weld heat treatments provides an effective route to enhance the strength of 3D-printed AlSi10Mg components for such applications. Ageing at 170 °C for 2 h increased joint strength by 22% through Cu diffusion, while cryogenic treatment at −190 °C for 24 h produced an additional 54% improvement driven by grain refinement. Microstructural analysis shows that the enhanced performance results from Cu-solute strengthening, a more favourable Si-phase distribution, and preserved solid-solution content. These findings show that well-designed heat treatments can effectively overcome weld softening and produce high-strength joints suitable for automotive and aerospace applications.

Genuine diffusion bonding (DB) of aluminium alloys on a practically usable scale has yet to be fully demonstrated for industrial applications. This study presents the successful fabrication of large-sized DB samples of AA6061 aluminium alloy without interlayers and evaluates the mechanical integrity of the bonded interfaces through tensile and shear tests. Notably, tensile testing – seldom performed in previous literature due to limited sample dimensions – was conducted on specimens extracted from the diffusion-bonded assemblies. The results reveal that under optimised process conditions, the bonded interface can attain mechanical performance comparable to the monolithic parent alloy, indicating near-100% bonding efficiency.

Electric vehicles are gaining popularity as an effective alternative for reducing carbon dioxide emissions and achieving carbon neutrality. Welding copper (Cu) and aluminum (Al) is applied to electric vehicle batteries due to their high conductivity and lightweight properties. However, welding Cu and Al may lead to the formation of intermetallic compounds (IMCs) within the weld zone, which deteriorates mechanical properties. This study analyses the tendency for cracks to occur and the causes of crack formation by welding Al and Cu materials based on nickel (Ni) coating thicknesses (0, 7, 25, and 50 µm) using a green laser. Observations of cracks in the weld zone and the corresponding Ni content, performed using an optical microscope and an electron probe micro-analyser, revealed that increased Ni coating thickness led to higher Ni content in the weld zone and a corresponding decrease in crack occurrence. In addition, micro-structural analysis of the weld zone using a scanning electron microscope revealed that cracks began to occur with the formation of Cu-Al IMCs and propagated in regions where CuAl and CuAl 2 phases were present. The formation of the NiAl phase, due to the increased Ni content in the weld zone, inhibited the reaction between Cu and Al, thereby suppressing the formation of these brittle IMCs. Consequently, crack initiation and propagation were effectively reduced. A shear test was conducted to evaluate mechanical performance. The results showed that the shear strength of the weld with a Ni coating thickness of 25 µm improved by approximately 203% compared to the weld without Ni coating. The shear strength of the weld with a 50 µm Ni coating thickness decreased compared the 25 µm sample due to the non-uniform formation of equiaxed and columnar grain structures.

This paper introduces a combined joining approach that integrates spatially arranged combined twin-wire arc welding with single-wire arc welding based on additive manufacturing technology to join Ti–6Al–4V and Inconel 718. Copper (S214), vanadium (V01), and niobium (Nb01) alloy wires were employed to fabricate a 3 mm thick multi-pass joint consisting of Ti–6Al–4V/V/Cu/Inconel 718 buttering and backing joint and Ti–6Al–4V/Nb/Cu/Inconel 718 filling joint. No intermetallic compounds were detected at the Ti–6Al–4V/Inconel 718 joint, and the phase composition of the V/Cu and Nb/Cu interfaces included V(S,S)+Cu(S,S) and Nb(S,S)+Cu(S,S), (S,S denotes solid solution), respectively. The joint fractured at the Cu weld and had a tensile strength of 390 MPa. This approach provides a novel strategy for dissimilar-metal joining which will expand industrial applications.

In the present study, a TA2/Q235 cladded pipe has been successfully fabricated by using explosive welding. The microstructure at the cladding interface was investigated using optical and electron microscopy-based techniques, which revealed a distinctive wavy bonding morphology at the TA2/Q235 interface. The presence of detrimental intermetallic compounds such as FeTi or Fe 2 Ti was not observed at the interface, contributing to an enhanced bonding quality. Compression testing further revealed a high-quality bonding of TA2/Q235 cladded pipes. Nano-indentation measurements showed enhanced hardness values in both Q235 and TA2 regions compared with the base materials, which substantiates the effectiveness of the optimised welding parameters.

Weld distortion and thinning critically affect the quality of friction stir welded (FSW) thin-walled sheets. Here, in-situ rolling FSW (IRFSW) was proposed to join 7075-T6 sheets with co-controlling distortion and weld thinning. The novel IRFSW tool was composed of inner and outer double-shoulders and circumferential rolling balls. The double-shoulder structure suppresses material overflow and the rolling balls regulate surface residual stress. The IRFSW process produced defect-free joints with minimal thinning (0.03 mm), whose surface finish was improved by 80.7%, and the longitudinal and transverse distortions of the IRFSW joint were reduced by 83.7% and 62.1% compared with those of the conventional joints. The ultimate tensile strength of the IRFSW joint reached 483 ± 2 MPa, retaining 86.1% of the base material's tensile strength. This study will provide powerful technical strategy and theoretical support for achieving low distortion and micro-thinning friction stir welding of thin sheets.

A prior estimation of the temperature field and bead profile can help fabricate dimensionally consistent and structurally sound parts using wire arc directed energy deposition (DED-Arc). We present here a three-dimensional analytical heat transfer model with a volumetric heat source to compute the transient temperature field and melt pool dimensions for DED-Arc. The analytical model considers the thermal conductivity and volumetric heat capacity as a linear function of temperature. In contrast to assuming a pre-defined deposited track profile, the same is scaled from the analytically computed melt pool dimensions into the substrate. The computed deposit profiles of single and multiple tracks and layers are validated extensively with the corresponding experimentally measured results for a range of DED-Arc process conditions.

Herein, a novel sandwich-structured interlayer (Ag30Cu37Zn32Sn/Cu 51.25 Zn 26.25 Ni 9 /Ag30Cu37Zn32Sn) was designed to transient liquid phase (TLP) bonding GH4169D superalloys. The interfacial microstructure, mechanical properties and fracture behaviour of GH4169D joints were investigated. The bonded interface was composed of (Ag, Cu, Zn) ss and (Cu, Zn, Ni) ss . A wider diffusion-affected zone including (Cu, Zn, Ni) ss and Cr-rich (Cr, Fe, Co) ss was formed at the interface with Ni 9 interlayer. A shear strength of 598 MPa was obtained at 890 °C for 80 min. (Ag, Cu, Zn) ss possessed low interface stiffness due to its small Young's modulus and Poisson's ratio. During the shear process, the soft-hard interface between (Ag, Cu, Zn) ss and (Cu, Zn, Ni) ss was prone to stress concentration, which induced initial crack initiation.