最新刊期
卷 54 ， 期 10 ， 2024
- 摘要：This article investigated the effects of different heat treatment regimes on the microstructure and mechanical properties of Ti-6Al-4V alloy fabricated by laser arc composite additive manufacturing. The changes in microstructure under different heat treatment parameters were analyzed using optical microscopy and scanning electron microscopy, and the reasons for the changes in mechanical properties of the samples under different solid solution temperatures and cooling rates were explored. The results showed that the microstructure of Ti-6Al-4V alloy fabricated by laser arc composite additive was mainly composed of Widmanstein Flat noodles structure and a small amount of acicular α phase in columnar β grain extending outward from the substrate along the deposition direction. After solution aging heat treatment, the microstructure was mainly a typical interlaced basket structure, the thickness of Flat noodles was significantly reduced, and the plasticity and toughness of the sample were significantly improved. When the solution aging heat treatment scheme was 950 ℃/1 h, AC+540 ℃/6 h, AC, compared with the deposited sample, the grain size was reduced by 2 times and better comprehensive mechanical properties could be obtained. It was recommended to adopt this heat treatment scheme.关键词：composite additive manufacturing;Ti-6Al-4V alloy;heat treatment;microstructure;mechanical property
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发布时间：2024-10-12 - 摘要：In order to improve the surface wear resistance of titanium alloy materials, TC4 (Ti-6Al-4V) was selected as the matrix material in this paper. A certain proportion of diamond and graphite particles were added to TiZrCuNi brazing material to make a composite coating material. The diamond composite brazing coating on TC4 was achieved by induction brazing under argon protection. The effect of graphite addition on the microstructure and wear resistance of composite coatings was studied, revealing the interaction mechanism between the active element Ti and diamond and graphite. The research results indicate that after adding graphite, the composite coating is mainly composed of diamond, TiC, Ti2Cu, ZrC, Zr2Cu, NiZr2, and residual graphite. Due to the presence of a large number of helical dislocations in graphite, it provides nucleation sites for TiC, allowing it to grow along the dislocations, thus evolving the growth mode of TiC into enveloping growth and ultimately forming a hexagonal shape. The addition of graphite weakens the wear resistance of the composite coating to a certain extent, but can increase the cutting edge rate of diamond particles, thereby improving grinding efficiency.关键词：TC4;diamond;brazing coating;graphite;wear resistance
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发布时间：2024-10-12 - 摘要：The study aims to investigate the fatigue crack growth behavior in different regions of a 12 mm thick TC4 titanium alloy laser-MIG hybrid welded joint and to analyze the interaction between microstructure and crack growth. Volume microscopy, phase microscopy, scanning electron microscopy, and electron backscatter diffraction (EBSD) techniques were used to explore the crack growth rates in different parts of the joint, the changes in crack growth paths, the interaction between microstructure and crack growth in different joint regions, and the deformation characteristics of the tissue around the crack tip. The results show that in the stable crack growth phase, the crack growth rate in the base metal area is the highest, which is 1.16 times and 1.81 times that of the heat-affected zone and the weld zone, respectively. When ΔK = 20 MPa·m1/2, the crack growth rate in the base metal is 3.39×10-4 mm/cycle. The IPF map at the crack tip indicates that the proportion of large-angle grain boundaries in the weld zone is 36.36%, which is higher than the 11.91% in the base metal and the 11.65% in the heat-affected zone. The presence of large-angle grain boundaries causes the crack to deflect along the grain boundaries or consume more energy to pass through the grain boundaries, increasing the crack growth resistance and showing better crack growth resistance. The base metal and heat-affected zone exhibit a mixed fracture mode of intergranular brittle fracture and ductile fracture, while the weld zone mainly shows a ductile fracture mode. In addition, EBSD analysis results show that the weld zone near the crack tip has a higher geometric dislocation density, and dislocations accumulate at the martensite boundary, causing the crack to deflect along the grain boundary, further hindering crack growth. Schmidt factor analysis also shows that the difference in orientation between the weld zone tissues is large, resulting in a higher crack growth threshold. In conclusion, the presence of a large number of large-angle grain boundaries and high dislocation density in the weld zone is the main reason for the higher crack growth resistance in the weld zone.关键词：titanium alloy;fatigue crack growth;laser-MIG hybrid welding;fracture mode;crack tip;crack growth behavior
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发布时间：2024-10-12 - 摘要：The aim of this paper is to study the influence of Ce-group rare earth elements on the solidification structure, solid solution structure, aging precipitation behavior, and properties of high-performance silicon white copper solder. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA) were used to observe the microstructure and test the properties of Cu-Ni-Si solders with different Ce contents. The results show that the addition of Ce-group rare earth elements significantly refines the solidification structure of the silicon white copper solder, reducing the grain size from 200 μm to 40 μm after addition. The addition of Ce elements inhibits the solid solution recrystallization process of the solder and refines the recrystallized grain size, increasing the recrystallization temperature from 900 ℃ to 950 ℃ and reducing the recrystallized grain size from 180 μm to 90 μm. The addition of Ce elements can promote the precipitation of Ni and Si elements and inhibit the growth of precipitated phases during the over-aging stage, but it does not change the type of aging precipitated phases, which are disk-shaped δ-Ni2Si and rod-shaped β-Ni3Si. The Cu-3.2Ni-0.75Si-0.06Ce silicon white copper solder achieves the best performance after aging at 450 ℃ for 4 h, with a tensile strength of 747 MPa and a shear strength of 454 MPa. Compared to the Cu-3.2Ni-0.75Si solder without Ce elements, the tensile strength is increased by 117 MPa, an increase of 18.6%, and the shear strength is increased by 91 MPa, an increase of 25%.关键词：silicon white copper solder;Ce element;solution treatment;aging precipitation;tensile strength
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发布时间：2024-10-12 - 摘要：This article uses a laser spiral welding system equipped with a vibrating mirror and a robot to weld 1 mm high-strength steel for automobiles. In order to evenly distribute the heat input of the solder joint, a type of Archimedean spiral was designed, with an outer diameter of 5.0 mm for the scanning path. The spiral is composed of multiple semicircles and a 5 π mm circular path on the periphery, R1=0.5 mm，R2=1.0 mm，R3=1.5 mm，R4=2.0 mm，R5=2.5 mm. The fracture behavior of laser spiral spot welding was analyzed, and the stress process, crack propagation path, and fracture surface during the tensile shear process of laser spiral spot welding were studied. Under the action of tensile and shear forces, the main fracture failure modes of laser spiral spot welding are single-sided weld tearing fracture and double-sided weld tearing fracture. The initiation and propagation of cracks are both along the boundary between the fusion zone and the heat affected zone. The proportion of large angle grain boundaries affected by coarse grain heat is relatively small at 18.69%, with a maximum KAM mean of 0.65. The stress and strain present are relatively large, making cracks more likely to initiate and propagate in the coarse grain heat affected zone.关键词：laser spiral spot welding;high-strength steel for automobiles;fatigue fracture;failure modes;scan path
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发布时间：2024-10-12 - 摘要：The mechanical TIG was used to weld the large diameter pipe ring seam of iron-nickel based alloy HT700P. After the welding and stabilization heat treatment (980 ℃/3 h/AC) was qualified by non-destructive testing (100% PT+100% RT+100% PAUT), the welded joint was subjected to tensile strength, bending, hardness performance, impact, high temperature endurance performance, and microstructure tests. The test results showed that the tensile strength and yield strength of the welded joint at room temperature were higher than the lower limit of the HT700P alloy, and the bending test was qualified. The hardness of the BM and HAZ in the welded joint is significantly higher than weld seam, while there is no significant difference in hardness between the base metal and heat affected zone. The average room temperature impact at the weld seam is 160.7 J, and at the HAZ is 102.3 J, both of which are higher than the lower limit of the HT700P alloy. The persistent strength of the welded joint for 105 hours is σ=138.3 MPa. The macro and micro metallographic structure of the welded joint is qualified, and the microstructure of the weld is austenite without the precipitation of harmful phases such as TCP.关键词：HT700P iron-nickel based alloy;TIG;mechanical property;microstructure;650 ℃ ultra-supercritical power plant
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发布时间：2024-10-12 - 摘要：Laser-arc hybrid welding with a laser leading method was employed to conduct welding tests on the 6082-T6 aluminum alloy lock-bottom joints commonly used in high-speed train bodies. By varying the size of the horizontal and vertical gaps, the effects on weld formation, penetration depth, weld width, and porosity were studied, and validated using the Fluent numerical simulation software. The results indicate that as the horizontal gap increases, both the penetration depth and weld width of the welded joint show a trend of gradual increase. In particular, when the horizontal gap increases from 0 mm to 1.2 mm, the penetration depth and the lower weld width increase from 5.91 mm and 1.65 mm to 6.45 mm and 2.46 mm, respectively, mainly due to the increase in laser welding heat input. Additionally, the joint porosity shows a trend of first decreasing and then increasing. When the horizontal gap is 0.7 mm, the porosity reaches a minimum of only 9.21%, which is lower than 10.86% with no gap and 12.61% with a 1.2 mm gap. This indicates that a certain horizontal gap size is beneficial for improving the stability of the keyhole, while an excessively large horizontal gap size may cause the keyhole stability to deteriorate. Moreover, with the increase of the vertical gap, although there is no significant change in the penetration depth and weld width of the joint, the porosity shows a continuous increasing trend, from 10.86% to 15.85%, indicating that the presence of a vertical gap is not conducive to maintaining the stability of the molten pool keyhole. The optimal assembly gap size is: 0.7 mm horizontal gap and 0 mm vertical gap. This study will provide process guidance for achieving high-quality welding of aluminum profiles for high-speed trains using laser-arc hybrid welding technology, and expand the application range of laser-arc hybrid welding in related fields.关键词：laser-MIG hybrid welding;assembly gap;weld formation;porosity
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发布时间：2024-10-12 - 摘要：The study on the performance of S355J2W+N weathering steel welded joints using non-copper coated welding wire OK AristoRod 13.26 involved MAG welding tests on 12 mm thick steel. The research methods included tensile testing, bending testing, impact testing, hardness testing, metallographic structure analysis, and fracture surface analysis. The results indicate that the welded joints of S355J2W+N weathering steel using non-copper coated welding wire exhibit good tensile and bending properties, with tensile strength and yield strength higher than the standard values of the base material, and the fracture surface shows characteristics of ductile fracture. The impact toughness of the weld is lower than that of the heat-affected zone and decreases with decreasing temperature, but both meet the standard requirement that the impact energy of the base material should not be less than 27 J (-20 ℃). The hardness of various regions of the welded joint conforms to the ISO15614-1 standard, all being less than HV380, with the base material having the lowest hardness, the over-heated zone the highest, and the greatest fluctuation in hardness observed in the heat-affected zone. Metallographic structure analysis shows that the welded joint consists of weld zone, over-heated zone, phase transformation recrystallization zone, and incomplete phase transformation recrystallization zone, with the phase transformation recrystallization zone having fine and uniform structures, exhibiting the best performance. The performance of S355J2W+N weathering steel welded joints using non-copper coated welding wire meets the production standard requirements.关键词：non-coppperd wire;S355J2W+N;mechanical properties;metallographic structure;fracture characteristic
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发布时间：2024-10-12 - 摘要：With the development of marine oil exploitation technology, the corrosion resistance of high-strength steel welded joints has become a critical issue. This paper aims to study the corrosion behavior of the heat-affected zone (HAZ) of E690 low-alloy high-strength steel MAG welded joints in a simulated marine environment, and to analyze the corrosion mechanism. The study uses a 3.5% NaCl solution as the corrosive medium for immersion tests. Techniques such as optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy are employed to observe and analyze the microstructure, mechanical properties, corrosion morphology, and corrosion product composition in different regions of the HAZ. The results indicate that the corrosion degree of different regions in the HAZ decreases in the order of overheated zone (GRHAZ) > normalized zone (CHAZ) > mixed grain zone (CGHAZ). The GRHAZ has the least amount of corrosion products, which are evenly distributed, and no large-area corrosion occurs. The corrosion products are primarily composed of two compounds, Fe3O4 and Fe2O3, with a structure characterized by nodular and columnar shapes. The CHAZ and CGHAZ have relatively more corrosion products, which are unevenly distributed, and localized areas of enhanced corrosion are observed in the CHAZ. When designing welded joints, the corrosion sensitivity of the HAZ should be fully considered, and appropriate protective measures should be taken to ensure the safety and reliability of offshore platforms.With the development of marine oil exploitation technology, the corrosion resistance of high-strength steel welded joints has become a critical issue. This paper aims to study the corrosion behavior of the heat-affected zone (HAZ) of E690 low-alloy high-strength steel MAG welded joints in a simulated marine environment, and to analyze the corrosion mechanism. The study uses a 3.5% NaCl solution as the corrosive medium for immersion tests. Techniques such as optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy are employed to observe and analyze the microstructure, mechanical properties, corrosion morphology, and corrosion product composition in different regions of the HAZ. The results indicate that the corrosion degree of different regions in the HAZ decreases in the order of overheated zone (GRHAZ) > normalized zone (CHAZ) > mixed grain zone (CGHAZ). The GRHAZ has the least amount of corrosion products, which are evenly distributed, and no large-area corrosion occurs. The corrosion products are primarily composed of two compounds, Fe3O4 and Fe2O3, with a structure characterized by nodular and columnar shapes. The CHAZ and CGHAZ have relatively more corrosion products, which are unevenly distributed, and localized areas of enhanced corrosion are observed in the CHAZ. When designing welded joints, the corrosion sensitivity of the HAZ should be fully considered, and appropriate protective measures should be taken to ensure the safety and reliability of offshore platforms.关键词：E690 low-alloy high-strength steel;MAG welding;microstructure;corrosion resistance;corrosion products
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发布时间：2024-10-12 - 摘要：To design a reasonable induction coil structure and investigate the effects of different input currents and heating times on the maximum value of the weld temperature, and to select suitable process parameters, so as to realise the high-efficiency preparation of honeycomb plate induction brazing. In this paper, a finite element model of induction brazing honeycomb plate is established, three shapes of coils are designed: spiral coil, double-back coil, M-shaped coil, and the temperature field distributions of induction brazing honeycomb plate with the three kinds of coils are obtained by calculations, and the influences of different process parameters on the maximum value of the temperature are also investigated. On the basis of simulation, brazing test was carried out on honeycomb sandwich structure composed of Ti2AlNb alloy and high-temperature alloy, and it was verified that induction brazing Ti2AlNb/GH4099 honeycomb sandwich structure had good feasibility. The helical coil concentrates the magnetic field more at the weld seam, generates more electromagnetic heat, and has a higher brazing efficiency. The spiral coil is more conducive to the generation of a large amount of electromagnetic heat in the induction brazing process, and the brazing efficiency is highest when the current is 1000A and the heating time is 15s, and the mechanical properties of the experimentally obtained Ti2AlNb/GH4099 honeycomb sandwich structure are excellent.关键词：Ti2AlNb;GH4099;induction brazing;finite element analysis;temperature field
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发布时间：2024-10-12 -
Study on the Preparation Process of Novel Composite Solder Sheet Based on Powder Pressing Technology
摘要：This study aims to investigate the application of powder pressing technology in the preparation of composite solder sheets and to research the effects of different pressing process parameters on the mechanical properties, microstructure, and brazing performance of composite solder sheets. SAC305 alloy powder and self-developed flux were pre-mixed and then pressed into composite solder sheets using powder pressing technology. A three-level three-factor orthogonal experiment was designed to analyze the effects of pressure, pressing temperature, and pressing time on the properties of the composite solder sheets. The results show that pressure is the most significant pressing parameter affecting the properties of the composite solder sheets. When the pressure is insufficient, the microstructure of the composite solder sheet exhibits distinct interface distinctions between tin alloy powder particles, with a small powder deformation and a high porosity. With increasing pressure, the powder undergoes obvious deformation, the interfaces become blurred, and the porosity decreases. The effects of pressing temperature and pressing time on the brazing performance of the composite solder sheets are significant, as high temperatures or prolonged pressing times can lead to increased oxidation of the tin powder and reduced flux activity, thereby decreasing brazing performance and increasing the rate of post-welding porosity. The effects of different process parameters on brazing expansion rate and cavity rate are relatively small. Composite solder sheets prepared under the conditions of 5,000 MPa pressure, 30 s pressing time, and 60 ℃ temperature exhibit good brazing performance, with a minimum porosity of 7.2% and certain self-strength. These sheets demonstrate good wettability on nickel sheets and a post-welding cavity rate of less than 0.1%. Compared with traditional pre-formed solder sheets with surface-applied flux, the powder-pressed composite solder sheets have equivalent brazing performance and higher yield, making them technically feasible for batch application.关键词：solder sheet;powder pressing;soldering property;pressing technology- 3
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发布时间：2024-10-12 - 摘要：This paper proposes a data-driven intelligent welding technology for ships unit assembly structure, which is difficult to apply due to the large assembly size, complex structure, and many obstacles in ships. The simulation scene is constructed through a 3D model of ship assembly and a gantry robot. The method of combining breadth search and depth search is used to efficiently identify the node element characteristics of the ship structure, and the weld curve is extracted by fitting the intersection line of the spatial 3D structure. A collision detection mechanism and obstacle avoidance rules for safe welding production space are established to accurately guide multi robot obstacle avoidance and automatic welding operations. The results indicate that the adoption of this intelligent welding technology has improved the efficiency and quality of intermediate assembly welding, promoted the automation and digital production of shipbuilding, and enhanced the intelligence and advanced process technology level of the shipbuilding industry.关键词：hull;welding;robot application;intelligent manufacturing
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发布时间：2024-10-12 - 摘要：In order to improve the application performances of remanufactured and repaired aluminum alloys, especially its fatigue performance and corrosion resistance, this paper took the representative Al-Zn-Mg alloy plate used in rail transit as the research object, and simulated the damage caused by actual service conditions on the alloy based on the experiments of the fatigue behaviors. The cracked sample alloy was repaired by different electric arc cladding processes and laser shock peening techniques. The differences in application performances between the repaired and unrepaired alloys were comprehensively compared. It is found that the combination of electric arc cladding and laser shock peening can greatly improve the fatigue performance and corrosion resistance of the studied alloy compared with the traditional electric arc cladding processes. The research results can provide theoretical basis and scientific guidance for extending the service life and controlling corrosion of aluminum alloy structural components used in rail transit.关键词：Remanufactured and repaired Al-Zn-Mg alloy;Electric arc cladding;Laser shock peening;fatigue performance;Corrosion resistance
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发布时间：2024-10-12 - 摘要：High-strength aluminum alloy plates can experience a decrease in performance and a reduction in service life due to the presence of the heat-affected zone (HAZ) during the welding process. To investigate the effects of temperature testing on high-strength aluminum alloy plates and to optimize welding process parameters and plate selection, a systematic study was conducted on the temperature gradient in the HAZ and the interlayer temperature. Three methods were employed for heating simulation tests on the high-strength aluminum alloy plates: local heating, homogenized heating simulation, and interlayer temperature simulation in the HAZ. Comparative analyses were conducted on the microhardness, strength, elongation, microstructure, and grain size of the plates at different temperatures. The study found that the hardness of the high-strength aluminum alloy plates first increased and then decreased with the rise in temperature, with 500 ℃ being the inflection point temperature for solid solution strengthening. Solid solution treatment could enhance the mechanical properties of the plates, but excessively long solution treatment times could lead to coarse grains and reduce the strengthening effect. During welding, the HAZ affected the plate properties within approximately 6 mm, and beyond 9 mm, the plate properties exhibited a gradient distribution. Adjusting the local heating simulation process could homogenize the gradient distribution of thermal field energy during welding, resulting in aluminum alloy plates with excellent post-welding performance distribution.关键词：high-strength aluminum alloy;thermal simulation;heat affected zone;temperature test;welding process
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发布时间：2024-10-12
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