A novel Ti cored wire containing Ti B2,Al60 V40 and Ti6 Al4 V mixed powders was developed for wirefeed arc deposition of Ti B/Ti composite coating,to enhance the hardness and wear resistance of Ti alloy.Results showed...A novel Ti cored wire containing Ti B2,Al60 V40 and Ti6 Al4 V mixed powders was developed for wirefeed arc deposition of Ti B/Ti composite coating,to enhance the hardness and wear resistance of Ti alloy.Results showed that after experiencing several chemical reactions,the wire was melted in the arc zone and turned into nonuniform droplets composed of Ti-Al-V-B melt and undecomposed Ti B2 particles.With the increase of welding current,the detachment time of droplet shortened while the transfer frequency accelerated,accompanied by the improvement in coating surface quality.The spatial distribution of Ti B whiskers in coating was governed by welding current.A uniform distribution could be achieved as welding current was sufficient at the expense of elevated dilution ratio,while increasing wire feeding speed could compensate the dilution loss of Ti B whisker to some extent.The decomposition process of Ti B_(2)particles and the microstructure evolution mechanism of coating was discussed in detail.The optimum coating possessed uniform microstructure,relatively low dilution ratio,and high hardness(639.1 HV_(0.5))as compared with Ti6 Al4 V substrate(326 HV_(0.5)).Indentation morphology analysis verified the excellent performance was ascribed to the load-sharing strengthening of Ti B whiskers.This study provides a high-efficiency fabrication method for the ever-developing titanium matrix composites(TMCs)coating.展开更多
This study carried out the underwater and in-air wire-feed laser deposition of an aluminium alloy with a thin-walled tubular structure. For both the underwater and in-air deposition layers, both were well-formed and i...This study carried out the underwater and in-air wire-feed laser deposition of an aluminium alloy with a thin-walled tubular structure. For both the underwater and in-air deposition layers, both were well-formed and incomplete fusion, cracks, or other defects did not exist.Compared with the single-track deposition layer in air, the oxidation degree of the underwater single-track deposition layer was slightly higher.In both the underwater and in-air deposition layers, columnar dendrites nucleated close to the fusion line and grew along the direction of the maximum cooling rate in the fusion region(FR), while equiaxed grains formed in the deposited region(DR). As the environment changed from air to water, the width of DR and height of FR decreased, but the deposition angle and height of DR increased. The grain size and ratio of the high-angle boundaries also decreased due to the large cooling rate and low peak temperature in the water environment.Besides, the existence of a water environment benefitted the reduction of magnesium element burning loss in the DR. The microhardness values of the underwater deposition layer were much larger than those of the in-air layer, owing to the fine grains and high magnesium content.展开更多
Waveform control method was commonly adopted to reduce the spatter of CO2 arc welding and improve the weld formation. It certainly would reduce the self-regulation ability of arc due to the adoption of segmented const...Waveform control method was commonly adopted to reduce the spatter of CO2 arc welding and improve the weld formation. It certainly would reduce the self-regulation ability of arc due to the adoption of segmented constant current control which especially led to arc＂ blowout with the abrupt change oat＂ arc＂ length or downward welding. Therefore alterative wire-feed system based on arc voltage negative feedback was put forward to improve the .stability of arc＂ length in this paper. Double closed-loop and double fuzzy P1 regulation were adopted in this system. Fuzzy control of induced voltage was adopted in the inner-loop which improved the stability and fast response of wire-feed system. Fuzz）＂ control of arc＂ voltage negative feedback was used in the outer-loop whose output .served as the input of negative feedback regulation of inner-loop induced voltage. This method could remain arc＂ length and weld penetration unchan, ged on the basils of reducing spatter and improving formation and it was proved by downward welding tests.展开更多
In the automatic CO_2 arc welding, the alteration of the vertical distance between the welding torch and the workpiece has a strong effect on the welding parameters such as welding current and voltage, with the result...In the automatic CO_2 arc welding, the alteration of the vertical distance between the welding torch and the workpiece has a strong effect on the welding parameters such as welding current and voltage, with the result that the appearance and quality of weld are not steady. To weaken the influence of the distance alteration, a method is put forward in the paper. The method is that the alternate wire-feed control is used for compensating the welding current. On the basis of theoretical analysis, a static numerical model for alternate wire-feed control is established. The experiments show that the model-based regulation of the wire feed rate can compensate the welding current and ensure the appearance of weld. When the alteration of vertical distance between the torch and the workpiece is greater, not only is the wire feed rate regulated, but the output voltage of the power source is adjusted to ensure the appearance and quality of weld.展开更多
The low accuracy of wire arc additive manufacturing(WAAM)is one of the main factors limiting its development,and is detrimental to the mechanical properties of WAAM structures.This study primarily investigated the eff...The low accuracy of wire arc additive manufacturing(WAAM)is one of the main factors limiting its development,and is detrimental to the mechanical properties of WAAM structures.This study primarily investigated the effects of wire-feeding directions and positions of the molten pool on the quality and accuracy of unsupported WAAM.First,the three-dimensional(3D)morphology and volume of unsupported rods manufactured with different wirefeeding directions were quantitatively evaluated using a 3D scanning method.The effects of the wire-feeding direction and arc length on the volume and standard deviation of the unsupported rods are then discussed in detail.Finally,the influence of the wire-feeding direction on the quality and accuracy of unsupported WAAM is discussed and revealed by combining the temperature gradients,surface tension,and contact angles.The research revealed that feeding a wire into the high-temperature zone of the molten pool could reduce material spatter and achieve higher precision.The volume of the sample fed into the high-temperature zone was 120%of that fed into the low-temperature zone.This reduced not only the material waste but also the standard deviation of the diameter of the same group of samples.This research is of great significance and value for high-quality unsupported WAAM.展开更多
以φ1.2 mm TC4钛合金焊丝为原材料,通过激光同轴送丝增材制造技术,结合蛇形正交路径,系统研究了增材试件在不同方向和高度下的力学性能、截面形貌、晶粒度和晶粒取向等之间的联系。研究结果表明,优化工艺参数下,试件表面成形良好(银白...以φ1.2 mm TC4钛合金焊丝为原材料,通过激光同轴送丝增材制造技术,结合蛇形正交路径,系统研究了增材试件在不同方向和高度下的力学性能、截面形貌、晶粒度和晶粒取向等之间的联系。研究结果表明,优化工艺参数下,试件表面成形良好(银白色、无飞溅),内部无气孔、裂纹等缺陷(满足NB/T 47014.2—2015 I级要求)。微观组织分析显示,增材试样底部因多次热循环形成细小网篮组织,中上部的双态组织和魏氏组织特征更为明显。晶粒取向差随高度增加而减小(底部X/Y向分别为45.9°/43.1°,顶部降至37.8°/35.9°)。力学性能测试表明,横向与纵向的抗拉强度(差异2.57%)、断后伸长率(差异4.44%)及冲击韧性(52.6 J和55.3 J)均满足CCS《材料焊接与规范2023》中对TC4板材的要求。此外,由于增材过程中热循环的影响,下层沉积组织晶粒尺寸较小,硬度较高。增材试件在横向和纵向的晶粒度、晶粒取向和组织形态相近,力学性能的各向异性较小。本研究为TC4钛合金激光同轴送丝增材制造技术的工程化应用提供了重要的实验依据。展开更多
随着产品功能需求的日益复杂,单材料部件已难以满足需求,这推动了采用多元材料组合以拓宽零件功能边界的丝粉混合定向能量沉积(Wire-Powder Hybrid Directed Energy Deposition,WP-DED)技术的发展。然而,对WP-DED成形工艺的全面理解仍...随着产品功能需求的日益复杂,单材料部件已难以满足需求,这推动了采用多元材料组合以拓宽零件功能边界的丝粉混合定向能量沉积(Wire-Powder Hybrid Directed Energy Deposition,WP-DED)技术的发展。然而,对WP-DED成形工艺的全面理解仍显不足,尤其是对其技术瓶颈和潜在问题的认知缺失,阻碍了该技术的进一步创新与广泛应用。鉴于此,深入探讨了WP-DED技术的核心运行机制,将其按送料方式分为双侧向送料、粉同轴与丝侧向送料、丝同轴与粉侧向送料和丝粉同轴送料4类,并系统性地梳理和归纳了这些多元化的材料输送机制。同时,回顾了WP-DED技术的演进历程与研究进展,详细阐述了4种送料方式WP-DED技术的演变、优劣对比、工艺探索以及沉积层组织与性能的研究等,旨在为读者提供清晰的技术发展脉络。此外,还指出了WP-DED技术在实践应用中面临的关键技术难题,如熔池流动控制、热历史管理、颗粒分布优化等,为后续科研与工程实践提供了明确方向。最后,展望了WP-DED技术的未来发展趋势,涉及材料开发、机制探索、过程优化和技术创新等方面,旨在激发更多关于该技术的创新思考与实际应用探索。展开更多
基金financially supported by Key-Area Research and Development Program of GuangDong Province(2019B010942001)National Key R&D Program of China(No.2017YFB0703100)+1 种基金the National Natural Science Foundation of China[grant numbers 51822103,51731009 and 51671068]the Fundamental Research Funds for the Central Universities[grant number HIT.BRETIV.201902]。
文摘A novel Ti cored wire containing Ti B2,Al60 V40 and Ti6 Al4 V mixed powders was developed for wirefeed arc deposition of Ti B/Ti composite coating,to enhance the hardness and wear resistance of Ti alloy.Results showed that after experiencing several chemical reactions,the wire was melted in the arc zone and turned into nonuniform droplets composed of Ti-Al-V-B melt and undecomposed Ti B2 particles.With the increase of welding current,the detachment time of droplet shortened while the transfer frequency accelerated,accompanied by the improvement in coating surface quality.The spatial distribution of Ti B whiskers in coating was governed by welding current.A uniform distribution could be achieved as welding current was sufficient at the expense of elevated dilution ratio,while increasing wire feeding speed could compensate the dilution loss of Ti B whisker to some extent.The decomposition process of Ti B_(2)particles and the microstructure evolution mechanism of coating was discussed in detail.The optimum coating possessed uniform microstructure,relatively low dilution ratio,and high hardness(639.1 HV_(0.5))as compared with Ti6 Al4 V substrate(326 HV_(0.5)).Indentation morphology analysis verified the excellent performance was ascribed to the load-sharing strengthening of Ti B whiskers.This study provides a high-efficiency fabrication method for the ever-developing titanium matrix composites(TMCs)coating.
基金financially supported by the Fundamental Research Funds for the Central Universities (No. HIT.OCEF.2021036)。
文摘This study carried out the underwater and in-air wire-feed laser deposition of an aluminium alloy with a thin-walled tubular structure. For both the underwater and in-air deposition layers, both were well-formed and incomplete fusion, cracks, or other defects did not exist.Compared with the single-track deposition layer in air, the oxidation degree of the underwater single-track deposition layer was slightly higher.In both the underwater and in-air deposition layers, columnar dendrites nucleated close to the fusion line and grew along the direction of the maximum cooling rate in the fusion region(FR), while equiaxed grains formed in the deposited region(DR). As the environment changed from air to water, the width of DR and height of FR decreased, but the deposition angle and height of DR increased. The grain size and ratio of the high-angle boundaries also decreased due to the large cooling rate and low peak temperature in the water environment.Besides, the existence of a water environment benefitted the reduction of magnesium element burning loss in the DR. The microhardness values of the underwater deposition layer were much larger than those of the in-air layer, owing to the fine grains and high magnesium content.
文摘Waveform control method was commonly adopted to reduce the spatter of CO2 arc welding and improve the weld formation. It certainly would reduce the self-regulation ability of arc due to the adoption of segmented constant current control which especially led to arc＂ blowout with the abrupt change oat＂ arc＂ length or downward welding. Therefore alterative wire-feed system based on arc voltage negative feedback was put forward to improve the .stability of arc＂ length in this paper. Double closed-loop and double fuzzy P1 regulation were adopted in this system. Fuzzy control of induced voltage was adopted in the inner-loop which improved the stability and fast response of wire-feed system. Fuzz）＂ control of arc＂ voltage negative feedback was used in the outer-loop whose output .served as the input of negative feedback regulation of inner-loop induced voltage. This method could remain arc＂ length and weld penetration unchan, ged on the basils of reducing spatter and improving formation and it was proved by downward welding tests.
文摘In the automatic CO_2 arc welding, the alteration of the vertical distance between the welding torch and the workpiece has a strong effect on the welding parameters such as welding current and voltage, with the result that the appearance and quality of weld are not steady. To weaken the influence of the distance alteration, a method is put forward in the paper. The method is that the alternate wire-feed control is used for compensating the welding current. On the basis of theoretical analysis, a static numerical model for alternate wire-feed control is established. The experiments show that the model-based regulation of the wire feed rate can compensate the welding current and ensure the appearance of weld. When the alteration of vertical distance between the torch and the workpiece is greater, not only is the wire feed rate regulated, but the output voltage of the power source is adjusted to ensure the appearance and quality of weld.
基金supported by National Natural Science Foundation of China(Grant No.12102219)National Key Research and Development Program of China(Grant No.2022YFB4601900)。
文摘The low accuracy of wire arc additive manufacturing(WAAM)is one of the main factors limiting its development,and is detrimental to the mechanical properties of WAAM structures.This study primarily investigated the effects of wire-feeding directions and positions of the molten pool on the quality and accuracy of unsupported WAAM.First,the three-dimensional(3D)morphology and volume of unsupported rods manufactured with different wirefeeding directions were quantitatively evaluated using a 3D scanning method.The effects of the wire-feeding direction and arc length on the volume and standard deviation of the unsupported rods are then discussed in detail.Finally,the influence of the wire-feeding direction on the quality and accuracy of unsupported WAAM is discussed and revealed by combining the temperature gradients,surface tension,and contact angles.The research revealed that feeding a wire into the high-temperature zone of the molten pool could reduce material spatter and achieve higher precision.The volume of the sample fed into the high-temperature zone was 120%of that fed into the low-temperature zone.This reduced not only the material waste but also the standard deviation of the diameter of the same group of samples.This research is of great significance and value for high-quality unsupported WAAM.
文摘随着产品功能需求的日益复杂,单材料部件已难以满足需求,这推动了采用多元材料组合以拓宽零件功能边界的丝粉混合定向能量沉积(Wire-Powder Hybrid Directed Energy Deposition,WP-DED)技术的发展。然而,对WP-DED成形工艺的全面理解仍显不足,尤其是对其技术瓶颈和潜在问题的认知缺失,阻碍了该技术的进一步创新与广泛应用。鉴于此,深入探讨了WP-DED技术的核心运行机制,将其按送料方式分为双侧向送料、粉同轴与丝侧向送料、丝同轴与粉侧向送料和丝粉同轴送料4类,并系统性地梳理和归纳了这些多元化的材料输送机制。同时,回顾了WP-DED技术的演进历程与研究进展,详细阐述了4种送料方式WP-DED技术的演变、优劣对比、工艺探索以及沉积层组织与性能的研究等,旨在为读者提供清晰的技术发展脉络。此外,还指出了WP-DED技术在实践应用中面临的关键技术难题,如熔池流动控制、热历史管理、颗粒分布优化等,为后续科研与工程实践提供了明确方向。最后,展望了WP-DED技术的未来发展趋势,涉及材料开发、机制探索、过程优化和技术创新等方面,旨在激发更多关于该技术的创新思考与实际应用探索。
