Welding in the World最新文献

Magnesium alloys are increasingly sought after in aerospace, automotive, biomedical, and electronic applications due to their superior strength-to-weight ratio, but their relatively poor surface integrity and erosion resistance necessitate advanced modification strategies. In this study, the QH21 magnesium alloy was engineered for enhanced surface performance using friction stir processing (FSP) reinforced with hybrid TiO₂–ZnO ceramic coatings. The processing parameters were systematically optimized through Taguchi’s design of experiments (DOE) methodology employing an L16 orthogonal array, with four critical factors: tool rotational speed (800–1400 rpm), traverse speed (15–30 mm/min), axial force (4–10 kN), and reinforcement percentage (3–12%) selected for evaluation. Performance metrics were assessed in terms of erosion factor and microhardness, which directly reflect wear resistance and structural integrity. The results revealed that a parameter set comprising 1000 rpm rotational speed, 15 mm/min traverse speed, 6 kN axial force, and 9% reinforcement minimized the erosion factor to 0.000290, indicating superior surface consolidation and particle–matrix interfacial bonding. Conversely, the maximum microhardness of 109 HV was achieved at 1400 rpm, 25 mm/min, 6 kN, and 12% reinforcement, attributed to intense dynamic recrystallization, grain refinement, and effective dispersion strengthening. Overall, the study demonstrates that optimized hybrid-particle FSP markedly enhances the surface quality and mechanical resilience of QH21 magnesium alloy, rendering it highly suitable for next-generation lightweight structural and functional components. 

Beryllium-aluminum (BeAl) alloys are widely used in the aerospace industry for their low density, high stiffness, and excellent thermal stability. However, the significant physical and metallurgical differences between Be and Al render conventional fusion welding methods ineffective for achieving high-quality joints. This study applied both conventional FSW and heat-assisted FSW to weld as-cast BeAl alloys. Comparative analysis reveals that the heat-assisted FSW process, which involves preheating both the base material and the backing plate, significantly enhances the plastic flowability of the material during welding and effectively prevents the formation of tunnel defects and surface cracks. The elevated temperature during welding promotes dynamic recrystallization, resulting in notable grain refinement in the weld nugget and an increase in microhardness to approximately 330 HV, about 2.3 times that of the base material. However, local microstructural inhomogeneity and microcracks within the Be particles still reduce the tensile strength of the joint to some extent. This study demonstrates the promising potential of heat-assisted FSW for addressing the welding challenges of BeAl alloys and provides valuable insights for future process optimization.

This study investigates the influence of martensitic start temperature on residual stress and distortion. A double-sided fully welded T-joint was fabricated by welding a high-alloy base material (1.4318) with two different filler wire combinations (G19 9, G4Si1). The temperature distribution and distortion were measured during the welding process using thermocouples and displacement transducers. The thermo-metallurgical-mechanical effect was considered when computing a numerical simulation model for a T-joint geometry. A phase transformation model was incorporated to predict martensite formation during welding, with the martensite start temperature varied as a parameter. Further, the mechanical model was developed by integrating the thermal strains, phase strains, and mechanical strains. Results from numerical simulations and experimental measurements are compared and analyzed to assess the impact of martensite start temperature on residual stresses and distortion. From the findings, it was found that, at a reduced martensitic start temperature, there was a significant reduction in residual stresses and distortion.

We present a study of ultrasonically welded Al wire/Cu plate joints with novel plowing-induced patterning. Various plowing-induced surfaces were machined on Cu plate to improve the bonding mechanism of welded joints. The PS-4 group exhibited upgraded interfacial bonding, achieving an interface strength and maximum peel strength of 2605 N and 2349 N respectively. The maximum UTS value reached 96 MPa in stress/strain tests. Conductivity analysis showed welds in the PS-4 group had low resistivity (0.008–0.009 mΩ). Weld quality was poor in samples 2 and 3, where high-frequency ultrasonic signals decayed rapidly due to groove addition. In contrast, welds in samples 1 and 4 indicated better quality with slower signal decay. SEM analysis revealed dense, compact interfaces under 1600 J welding energy with no voids or irregularities. EDS scans showed 14.6% carbon content in horizontal positions and 10.5% in plowed areas. EBSD analysis of the SP-4 sample indicated that grain boundary distribution and texture planes were parallel to the rolling direction with a maximum grain size of 3.4 μm.

Twin wire arc additive manufacturing (T-WAAM) offers the capability to fabricate functionally graded material (FGM) tailoring in a variation of compositional elements and the related properties. In this context, two feedstocks, SS 316L (SS) and ER-70S6 (LCS), were used to fabricate a FGM structure using a T-WAAM setup integrated with gas-tungsten-arc-welding (GTAW) power source. The variation of elemental compositions of the fabricated structure was obtained by controlling the feed rate of the two different feedstock materials. The two extreme ends of the fabricated wall were made of pure SS and LCS, whereas the intermediate zones were fabricated by mixing 75% SS+25% LCS, 50% SS+50% LCS, and 25% SS+75% LCS. The intermixed zones exhibited complex microstructural, mechanical, and tribological phenomena. It showed duplex phase formation, i.e., austenite (FCC) and ferrite (BCC), where the microstructure varied from austenite+martensite to bainite+pearlite to polygonal ferrite. The average hardness and wear behaviour of these zones is better than that of pure SS and LCS. Maximum hardness value of 398 HV is observed at 50–50 SS and LCS mixing zone. This SS-LCS combination shows a remarkable surface durability and excellent wear resistance. The coefficient of friction, specific wear rate, and wear depth in this zone are 0.128, 0.01 × 10³ mm³/Nm and 2.687 µm, respectively. This research offers a feasible and flexible approach to fabricating FGM, tailored design, and renovation of components, where hardness and wear interaction are more prominent.

To improve the steel/titanium joint performance, nickel (Ni) and vanadium (V) interlayers were firstly deposited on the 304 stainless steel (SS) side and TC4 alloy side using a laser metal deposition (LMD) process, respectively. The deposited interlayers were then combined with a rolled CuCrZr plate as a composite interlayer for dissimilar laser welding of TC4/304 SS butt joints. The effects of two different thicknesses of Ni interlayers on the weld shape, microstructure, and mechanical properties of TC4/304 SS joints were investigated. The results show that a sound TC4/304 SS joint with full penetration is successfully obtained using the novel V/CuCrZr/Ni composite interlayer. The TC4/304 SS joint with a 1-mm-thick Ni layer of the composite interlayer exhibits an ultimate tensile strength (UTS) of 451.2 MPa and an elongation index (EI) of 2.8%. As the thickness increases from 0.5 to 1 mm, the Cu content in the fusion zone-2 (FZ-2) on the 304 SS side rises from 12.66 to 55.33%, and no Fe-Ti intermetallic compounds (IMCs) are formed. The increase of Ni layer thickness also leads to increased Fe and Ni contents in the unmelted CuCrZr zone, which is beneficial to enhance solid solution strengthening, and therefore to improve joint strength.

Friction stir welding (FSW) technology was employed for joining the selective laser melted (SLM) AlSi7Mg specimens, and the microstructures and mechanical properties of welded joints were elucidated. During FSW, the material underwent severe thermo-mechanical coupling effect, resulting in features of the welded zone completely distinct from the SLM base material: pore size and number were significantly reduced, the eutectic Si-rich phase transformed from a continuous network into discrete blocky particles (2–8 μm), and grain coarsening occurred in the heat-affected zone. Notably, the heat-affected zone became a weak position for fracture failure. Based on comprehensive experimental investigations and microstructural analyses, FSW was found to (i) reduce porosity in SLM AlSi7Mg welds by 83.6% and (ii) achieve 81.5% of SLM base material’s tensile strength alongside enhanced microhardness and density—outperforming traditional fusion welds such as argon arc welding. These results confirm the significant potential of FSW for joining SLM aluminum alloy components.

Graphical abstract

The age-hardenable aluminum alloy AW6082 combines high strength with good formability, but its weldability is limited due to precipitation dissolution and softening, as well as a high susceptibility to hot cracking. Conventional approaches often use dissimilar filler materials from the 4000 and 5000 series, which can result in reduced strength and limited hot cracking resistance. These challenges are addressed by the heat-treatable filler material AlMg0.7SiTiB. The alloyed TiB nanoparticles are expected to minimize the grain size, reduce the tendency to hot cracking, and improve strength values. Therefore, the aim of the investigations is to validate the welding of the aluminum wrought (AW) alloy AW6082 using the novel filler material AlMg0.7SiTiB in comparison to the standard filler alloy (AlSi5). Based on a process development, test specimens were manufactured in accordance with DIN EN ISO 15614-2:2005. Microstructural and mechanical properties were assessed through optical microscopy (OM), energy dispersive spectroscopy (EDS), tensile and 3-point bending test, and hardness testing. The evaluation was carried out for each filler material for both the as-welded and the artificially aged condition. Additionally, hot cracking resistance was evaluated using the self-restraint Houldcroft-Test. The results show a significant grain refinement of approximately 65% on average, along with a reduced susceptibility to hot cracking compared to the standard filler material. The evaluation of the mechanical-technological properties showed comparable values between the two filler materials. In summary, welding AW6082 with the TiB₂-modified filler material shows improved grain refinement and hot cracking resistance, indicating enhanced weldability compared to the standard filler material.

The influence of a post-weld heat treatment (PWHT) on the microstructure and mechanical behaviour of a 2.25Cr1Mo0.25 V weld was investigated. The study focused on three distinct regions: the base metal, the heat-affected zone (HAZ), and the weld metal. Due to the limitations in conducting standard mechanical tests on all the weld regions, particularly the HAZ, Small Punch Tests (SPT) were performed across all regions, while standard mechanical tests were conducted only when sufficient material was available. Microstructural characterisation involved microstructure identification, hardness profiling, X-ray diffraction measurements, and fractographic examination. The results demonstrate that the SPT method effectively characterises the mechanical behaviour of all weld regions. Furthermore, PWHT significantly enhances microstructural homogeneity and improves the mechanical performance of both the HAZ and weld metal. The treatment leads to relaxation of residual stresses and microstructural refinement, thereby increasing the resistance of welded components to mechanical failure.

The powder-feed underwater laser metal deposition (ULMD) of Ti6Al4V alloy was carried out in a local dry cavity generated by a special drainage nozzle, and the influence of laser power and scanning speed on the deposition appearance and geometry characteristics of a single track was investigated. The results show that as the laser power increases, the aspect ratio and dilution rate increase. With the scanning speed increasing, the aspect ratio increases, but the dilution rate and the deposition angle decrease. A high-quality ULMD single track with a uniform appearance and no metallurgical defects is obtained at the laser power of 2.2 kW and scanning speed of 14 mm/s. In addition, a thin wall part was fabricated using the optimal process parameters. The microstructure of the deposited metal is composed of acicular martensitic α′ phase, and the sizes of the martensitic in the top region are finer than those of the martensitic in the middle region and bottom region.