The brazing joint of the Ti-6Al-4V alloy was produced with a designed brazing filler alloy and the optimized brazing temperature which is lower than the β-phase transformation of the matrix. The ...strength and the ductility of brazing joined Ti-6Al-4V samples were evaluated by conventional tensile tests with a DIC 2D–strain field measurement. The Widmanstätten microstructure with no voids or cracks or intermetallic compounds was found throughout the joint with a width of β-lamellar as ~1μm. Due to the fine acicular α-Widmanstätten and β-lamellar, and the uniformly diffused filler elements throughout the entire joint, the strength of the joint was as much as the matrix. In addition, the hardness test results agreed well with the tensile strength tests. All fractures occurred in the matrix rather than the brazing joints. Furthermore, the maximum local tensile strain was measured as 20% in the matrix, while under the same stress, the brazing joint only reached 6.3% tensile plastic strain. Thus, the mechanical properties of the joint with the associated microstructure demonstrated that a successful brazing filler alloy has been developed for the Ti-6Al-4V alloy.
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•Fine and interlocking acicular Widmanstätten microstructure is formed across the entire brazing joint section.•Preferential grain orientations and the solid solution strengthening result in the ultimate strength of the brazed samples.•The localized strain distribution at the braze joint was measured as ~6.3%. All the fractures occurred in the matrix with local tensile strain up to 20%.
Fittings have extensive use in the aerospace, automotive, and other industries as they serve as sealing and connecting components for tube systems. External Swaging (ES) forming creates a permanent ...joint through plastic deformation of the metal. This technique is not dependent on the tube's wall thickness and offers benefits such as high-pressure resistance and effective sealing. Using the forming process of a 10 mm Ti-3Al-2.5 V tube with an adapted 21-6-9 fitting as an illustration, a three-dimensional finite element model for the entire assembly was developed. The model consists of the tube, fitting, elastic clamp, and crimping tool. The formation mechanism and joint strength of external swaging are analyzed by numerical simulation and experimental testing. The results show that during the extrusion process, the tangential contact between the extrusion tool and the elastic clamps converts external radial loads into circumferential loads, resulting in circumferential strains in the tube. Circumferential strain creates an arched sealing area between the tube and fitting contact surfaces, providing sealing and joint strength. The joint strength of 10.60 kN was determined through finite element simulation. The load required for forming is determined by analysis to be 80.13 kN. and the relationship between squeeze load, crimp volume and joint strength is clarified. The study revealed that the height of the arch area aligns with the connection strength's change rule concerning extrusion load, fitting the two found that when the external extrusion load changes, the two are linear rule of changing. Based on this, a method is suggested for forecasting the strength of a joint by measuring the height of the arch in the tube after forming.
•Explaining how the radial load is converted to circumferential loads to complete the external swaging•Investigation of the relationship between the extrusion load, extrusion volume, and connection strength after forming.•A novel approach for assessing the strength of a connection by measuring the arch's height.
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•Annealing improves the comprehensive properties of the hard-plate rolling plate.•Twin induction and shear band promoting recrystallization.•Annealing can improve the non-uniformity ...of thickness structure of hard-plate rolling plate.
When rolling aluminum (Al)/magnesium (Mg)/aluminum (Al) composite plates with large reduction, there are often differences in the matrix structure and hard brittle properties of interfacial intermetallic compounds, which have a negative impact on the mechanical properties. Therefore, it is necessary to adjust the evolution of the diffusion layer and homogenize the internal structure of the metal plate by annealing to achieve the best performance. In this study, Al/Mg/Al composite plates were formed by hard-plate rolling (HPR) with a single pass of 60% reduction and annealed. The results show that the tensile strength (UTS) of rolled plate is 235.4 MPa and the elongation to failure (A) is 6.2%. It is found that after annealing at 300 °C for 1 h, the interface bonding property is suitable, the microstructure is gradually uniformly refined by the joint action of shear band expansion and twin induced static recrystallization, the UTS reaches 265.1 MPa. The A is increased by 18.5%. In conclusion, annealing treatment can significantly improve the microstructure and connection strength of hard-plate rolling Al/Mg/Al composite plates and provide scientific guidance and technical support for the forming and manufacturing high-performance lightweight composite plates.
The effects of welding conditions such as the electrode type and welding current were investigated on the microstructure and joint strength of the resistance weld of A5052 and GA590. The reaction ...layer formed at the joint interface was inferred to consist of Fe-Al based intermetallic compounds (IMCs) which are FeAl, FeAl2, Fe2Al5 and FeAl3 by quantitative analysis. Although the thickness of the IMCs layer decreased from the center of the nugget towards the edge of it. When the DR type electrode was used, the cross tensile force became higher than those of the joints formed with the R type one. This is because the thickness of the reaction layer formed at the nugget end of A5052 was thin in the case of the DR type electrode. Also, it was found that cross tensile force increases when the thickness of the reaction layer is thin by multiple regression analysis.
The use of multi-materials structures is nowadays one of the most sought solutions to decrease weight and reduce both emission of greenhouse gases and fuel consumption in the automotive industry. ...Dissimilar joining of aluminum (Al) alloys to steels by fusion-based welding technologies is often difficult to achieve as a result of the significant mismatch in these materials’ physical and chemical properties. Moreover, when mixed in the liquid state, hard and brittle intermetallic compounds are easily formed. Due to characteristics that include high processing speed, flexibility and energy density, multiple attempts have been made to join Al to steel using laser-based processes. This thorough review article provides a comprehensive and exhausting analysis of the recent achievements and progress on joining of Al alloys to steel by various laser-based joining processes, including laser keyhole welding, laser welding-brazing, laser-arc welding, laser-assisted friction stir welding, laser roll pressure welding and joining based on laser additive manufacturing. This paper also evaluates the joining conditions, filler materials, phase constitution, microstructure, mechanical properties and joining mechanisms associated to each process. Furthermore, special emphasis is given to factors affecting the joint strength such as welding defects, joint geometry, intermetallic compounds formation and interfacial strength. The review is then concluded with an outlook providing the summary and future trends of this field.
Issue Title: Special Sections: Pb-free Solders and Materials for Emerging Interconnect and Packaging Technologies; Phase Stability, Phase Transformations, and Reactive Phase Formation in Electronic ...Materials XIII; and Advanced Materials for Power Electronics and Power Conditioning Systems We show that dilute Al additions can control the size of primary Cu^sub 6^Sn^sub 5^ rods in Sn-0.7Cu/Cu ball grid array joints. In Sn-0.7Cu-0.05Al/Cu joints, the number of primary Cu^sub 6^Sn^sub 5^ per mm^sup 2^ is 7 times higher and the mean three-dimensional length of rods is 4 times smaller than in Al-free Sn-0.7Cu/Cu joints, while the area fraction of primary Cu^sub 6^Sn^sub 5^ is similar. It is shown that epitaxial nucleation of primary Cu^sub 6^Sn^sub 5^ occurs on δ-Cu^sub 33^Al^sub 17^ or γ ^sub 1^-Cu^sub 9^Al^sub 4^ particles, which are stablein the Sn-0.7Cu-0.05Al melt during holding at 250°C. The observed facet relationships agree well with previously determined orientation relationships between δ-Cu^sub 33^Al^sub 17^ and Cu^sub 6^Sn^sub 5^ in hypereutectic Sn-Cu-Al alloys and result in a good lattice match with <2.5% lattice mismatch on two different interfacial planes.
This study investigates the effectiveness of incorporating different amino-functionalized carbon nanotubes (CNTs) and acrylic triblock copolymer (BCP) into an aerospace-grade relatively ...high-viscosity epoxy (EA9396) resin to enhance the lap shear and tensile butt-joint strength at room and elevated temperatures (90 °C). To address the common issue of nanoparticle agglomeration in epoxy resin, which is exacerbated by its relatively high viscosity, a novel processing method was developed. This method involves ozone oxidation followed by functionalization with either polyethyleneimine (P + oz-CNTs) or a polyamine hardener (H + oz-CNTs). The functionalization not only ensures uniform dispersion of carbon nanotubes (CNTs) but also enhances their chemical reactivity with both the epoxy and block copolymer (BCP) matrix. The bonding performance of the epoxy, incorporating functionalized CNTs and BCP, was evaluated using single lap shear and tensile butt-joint tests. The results emphasize the substantial enhancement of both lap shear and butt-joint strength in the BCP-modified epoxy with the incorporation of functionalized CNTs (P + oz-CNTs and H + oz-CNTs), evident at both room temperature and 90 °C. At ambient conditions, the lap shear strength of the nanocomposite adhesives (P + oz-CNT + BCP/EA9396 and H + oz-CNT + BCP/EA9396) exhibited significant improvements of 40 % and 48 % respectively. At 90 °C, both formulations demonstrated a 20 % increase in lap shear strength. Furthermore, considerable advancements were observed in butt joint strength, with enhancements of 22 % (P + oz-CNT + BCP/EA9396) and 28 % (H + oz-CNT + BCP/EA9396) at room temperature. Importantly, compared to the unmodified epoxy, the butt joint strength displayed even more remarkable improvements of 49 % (P + oz-CNT + BCP/EA9396) and 42 % (H + oz-CNT + BCP/EA9396) at 90 °C. The analysis of fracture studies showed that introducing amine functionalization resulted in a more consistent dispersion of CNTs and enhanced the ability of the BCP/EA9396 to undergo plastic deformation. The study further demonstrates that functionalization with PEI and amine hardener reduces CNT pull-out, which enhances energy dissipation mechanisms and increases lap shear and butt joint strengths.
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•Effective CNT functionalization methods were developed to enhance the dispersion and reactivity with high viscosity epoxy.•Solved the critical issue of CNT agglomeration in high viscosity epoxy using novel functionalization and 3-roll mill manufacturing methods.•At room temperature, the functionalized CNTs, combined with BCP, enhanced both lap shear and but joint strengths of epoxy by 40–48 % and 24–28 %, respectively.•At 90 °C, the lap shear strength enhanced by 20 %, whereas butt joint strength significantly improved by 42–49 %.•Discover the mechanism of the nanotechnology via microscale studies.
This work describes an electric-field assisted joining technique that is capable of joining 3 mol.% yttria stabilized zirconia (3YSZ) ceramics within 1 min at furnace temperature of 400 °C. The joint ...with 94–99% of the parent material’s three-point bending strength (638 ± 21 MPa) was achieved at furnace temperature of 600–900 °C by optimizing the key joining parameters, including the applied electric current, joining time and furnace temperature. Increase in current and joining time promoted the formation of dense joint, but they also led to degradation of the strength of parent material via defect accumulation. The furnace temperature enhanced the defect annihilation, which lowered the extent of strength degradation of the parent material. Therefore, the joint formed at high furnace temperature with threshold current and appropriate joining time displayed high strength. It was experimentally demonstrated that the electric field enabled the ultrafast joining, rather than the Joule heating.
The NiPdPtAu-Cr filler alloy was proposed for joining Cf/SiC composites. The wettability on Cf/SiC composite was studied by the sessile drop method at 1200°C for 30min. Under the brazing condition of ...1200°C for 10min, the Cf/SiC-Cf/SiC joint strength was only 51.7MPa at room temperature. However, when used a Mo layer, the Cf/SiC-Mo-Cf/SiC joint strength was remarkably increased to 133.2MPa at room temperature and 149.5MPa at 900°C, respectively. At the interface between Cf/SiC and Mo, Mo participated in interfacial reactions, with the formation of Cr3C2/Mo2C reaction layers at the Cf/SiC surface. The improvement in the joint strength should be mainly attributed to the formation of MoNiSi. The Cf/SiC-Mo joint strength was 86.9MPa at room temperature and 73.7MPa at 900°C, respectively. After 10 cycles of thermal shock test at 900°C the Cf/SiC-Mo joint strength of 71.6MPa was still maintained.
In this paper, the research advances on epoxy-based nanocomposites as adhesive materials are reported. The research and development of nanocomposite as an adhesive material by incorporating various ...nano-fillers including carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), nanoclay, nano-silica (nano-SiO2) and nano-alumina (nano-Al2O3) are reviewed. The effect of different nano-fillers on the mechanical properties and the joint strength of epoxy are reported. The current understanding of the principles and techniques for nano-fillers dispersion and the effects of nano-filler addition on the strength and durability of epoxy joints are also reviewed. The main findings are summarised and future research is recommended finally.
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