In order to solve the problem of porosity in laser deep penetration welding of GH3625 high-temperature alloy plates,five different ratios of high-purity helium gas and high-purity argon gas mixed gases were compared i...In order to solve the problem of porosity in laser deep penetration welding of GH3625 high-temperature alloy plates,five different ratios of high-purity helium gas and high-purity argon gas mixed gases were compared in welding experiments after various process parameter improvements and adjustments failed to achieve Class I welds.The experimental results show that using high-purity helium gas or a mixture of 50%high-purity helium gas and 50%high-purity argon gas can both achieve Class I welds.This indicates that using high-purity helium gas or an appropriate mixed gas instead of pure argon is one of the effective ways to solve the problem of porosity in laser deep penetration welding of high-temperature alloys.The mixture of 50%high-purity argon gas and 50%high-purity helium gas can reduce the consumption of high-purity helium gas,lower production costs,and is more suitable.展开更多
Laser surface alloying of γ TiAl alloy with nitrogen was studied under the constant protective nitrogen current (20l /min). The experimental results shown that the surface multi layers formed with experimental para...Laser surface alloying of γ TiAl alloy with nitrogen was studied under the constant protective nitrogen current (20l /min). The experimental results shown that the surface multi layers formed with experimental parameters could be up to 600μm depth; it consists of TiN,Ti 2AlN,α 2 and γ phases, without AlN, and the irregular coarse continuous “flow” line,dendrite,needle and granular nitrides disperse on the fine dendrite casting α 2 and γ phases substrate. The microstructure and compositions in the nitiding layer were determined and analyzed by SEM and EPMA and the mechanism for the formation of microstructure in the nitriding layer was also discussed.展开更多
In order to increase the absorption of laser energy and improve the weld appearance in laser welding of Al alloy, 1.8 mm- 6013 Al alloy plate was welded by activating flux CO2 laser welding. Activating flux includes o...In order to increase the absorption of laser energy and improve the weld appearance in laser welding of Al alloy, 1.8 mm- 6013 Al alloy plate was welded by activating flux CO2 laser welding. Activating flux includes oxide and fluoride, which was coated on the workpiece surface before welding. The experimental results show that the activating flux can effectively improve the absorption of CO2 laser energy and increase the amount of the molten base metal. The improvement on the absorption of laser energy by oxide activating flux is greater than that by fluoride activating flux or two-component activating flux, but the slag detachability made from both the single activating flux and two-activating flux is poor. The gas pore sensitivity with oxide activating flux is much higher than that with fluoride activating flux in CO2 laser welding of 6013 Al alloy.展开更多
High saturation magnetization and low coercivity are required for soft magnetic materials.This study investigated the Co_(47.5)Fe_(28.5)Ni_(19)Si_(3.3)Al_(1.7)high-entropy soft magnetic skeleton was prepared by select...High saturation magnetization and low coercivity are required for soft magnetic materials.This study investigated the Co_(47.5)Fe_(28.5)Ni_(19)Si_(3.3)Al_(1.7)high-entropy soft magnetic skeleton was prepared by selective laser melting.Then Al wpressure infiltrated into skeletons to obtain a dense composite material.The high-entropy composite materials possessed favorable compressive ductility and moderate soft magnetic properties.The high-entropy composite materials were obtained with Ms being 97.1 emu/g,79.8 emu/g,33 emu/g and possessing 19 Oe,15.8Oe and 17Oe of Hc,respectively.However,the magnetostriction coefficient remains low level,about 5ppm.These reported properties are attributed to the special structure of the material studied in present experiment.Nevertheless,a novel strategy of structural designing was proposed in this paper.展开更多
Titanium alloys have been successfully applied for aerospace, ship and chemical industries because they possess many good characteristics such as high specific strength, superior corrosion resistance and excellent hig...Titanium alloys have been successfully applied for aerospace, ship and chemical industries because they possess many good characteristics such as high specific strength, superior corrosion resistance and excellent high temperature resistance. Though these alloys show reasonable weldability characteristics, the joint properties are greatly influenced by the welding processes. Weld thermal cycle of the processes will control the weld metal solidification and subsequent phase transformation and resultant microstructure. The welded joints of Ti-6Al-4V alloy were fabricated by gas tungsten arc welding (GTAW), laser beam welding (LBW) and electron beam welding (EBW) processes. The joints fabricated by EBW process exhibit higher strength compared with the GTAW and LBW joints; but the joints by GTAW process exhibit higher impact toughness compared with the LBW and EBW joints. The resultant tensile and impact properties of the welded joints were correlated with the weld metal microstructures.展开更多
In order to study the effect of gas atmosphere on forming performance of laser powder bed fusion(LPBF),AlSi10 Mg alloy was prepared by direct forming and in situ laser remelting under the shielding gas of argon and ni...In order to study the effect of gas atmosphere on forming performance of laser powder bed fusion(LPBF),AlSi10 Mg alloy was prepared by direct forming and in situ laser remelting under the shielding gas of argon and nitrogen in this study,and its micro structure and properties were characterized and tested,respectively.The results show that the forming performance of AlSi10 Mg under nitrogen atmosphere is better than that of argon.Moreover,in situ laser remelting method can effectively enhance the relative density and mechanical properties of AlSi10 Mg,in which the densification is increased to 99.5%.In terms of mechanical properties,after in situ remelting,ultimate tensile strength under argon protection increased from444.85±8.73 to 489.45±3.20 MPa,and that under nitrogen protection increased from 459.21±13.77 to 500.14±5.15 MPa.In addition,the elongation is nearly doubled and the micro-Vickers hardness is increased by 20%.The research results provide a new regulation control method for the customization of AlSi10 Mg properties fabricated by LPBF.展开更多
文摘In order to solve the problem of porosity in laser deep penetration welding of GH3625 high-temperature alloy plates,five different ratios of high-purity helium gas and high-purity argon gas mixed gases were compared in welding experiments after various process parameter improvements and adjustments failed to achieve Class I welds.The experimental results show that using high-purity helium gas or a mixture of 50%high-purity helium gas and 50%high-purity argon gas can both achieve Class I welds.This indicates that using high-purity helium gas or an appropriate mixed gas instead of pure argon is one of the effective ways to solve the problem of porosity in laser deep penetration welding of high-temperature alloys.The mixture of 50%high-purity argon gas and 50%high-purity helium gas can reduce the consumption of high-purity helium gas,lower production costs,and is more suitable.
文摘Laser surface alloying of γ TiAl alloy with nitrogen was studied under the constant protective nitrogen current (20l /min). The experimental results shown that the surface multi layers formed with experimental parameters could be up to 600μm depth; it consists of TiN,Ti 2AlN,α 2 and γ phases, without AlN, and the irregular coarse continuous “flow” line,dendrite,needle and granular nitrides disperse on the fine dendrite casting α 2 and γ phases substrate. The microstructure and compositions in the nitiding layer were determined and analyzed by SEM and EPMA and the mechanism for the formation of microstructure in the nitriding layer was also discussed.
基金supported by State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, China
文摘In order to increase the absorption of laser energy and improve the weld appearance in laser welding of Al alloy, 1.8 mm- 6013 Al alloy plate was welded by activating flux CO2 laser welding. Activating flux includes oxide and fluoride, which was coated on the workpiece surface before welding. The experimental results show that the activating flux can effectively improve the absorption of CO2 laser energy and increase the amount of the molten base metal. The improvement on the absorption of laser energy by oxide activating flux is greater than that by fluoride activating flux or two-component activating flux, but the slag detachability made from both the single activating flux and two-activating flux is poor. The gas pore sensitivity with oxide activating flux is much higher than that with fluoride activating flux in CO2 laser welding of 6013 Al alloy.
基金National Natural Science Foundation of China(NSFC,Granted Nos.51671020)Guangdong Basic and Applied Basic Research Foundation(No.2019B1515120020)Creative Research Groups of China(No.51921001).
文摘High saturation magnetization and low coercivity are required for soft magnetic materials.This study investigated the Co_(47.5)Fe_(28.5)Ni_(19)Si_(3.3)Al_(1.7)high-entropy soft magnetic skeleton was prepared by selective laser melting.Then Al wpressure infiltrated into skeletons to obtain a dense composite material.The high-entropy composite materials possessed favorable compressive ductility and moderate soft magnetic properties.The high-entropy composite materials were obtained with Ms being 97.1 emu/g,79.8 emu/g,33 emu/g and possessing 19 Oe,15.8Oe and 17Oe of Hc,respectively.However,the magnetostriction coefficient remains low level,about 5ppm.These reported properties are attributed to the special structure of the material studied in present experiment.Nevertheless,a novel strategy of structural designing was proposed in this paper.
基金the Combat Vehicle Research and Development Establishment(CVRDE),Avadi,Chennai,Government of India for providing financial support to carry out this investigation through a Contract Acquisition for Research Services project,No.CVRDE/MMG/09-10/0043/CARS
文摘Titanium alloys have been successfully applied for aerospace, ship and chemical industries because they possess many good characteristics such as high specific strength, superior corrosion resistance and excellent high temperature resistance. Though these alloys show reasonable weldability characteristics, the joint properties are greatly influenced by the welding processes. Weld thermal cycle of the processes will control the weld metal solidification and subsequent phase transformation and resultant microstructure. The welded joints of Ti-6Al-4V alloy were fabricated by gas tungsten arc welding (GTAW), laser beam welding (LBW) and electron beam welding (EBW) processes. The joints fabricated by EBW process exhibit higher strength compared with the GTAW and LBW joints; but the joints by GTAW process exhibit higher impact toughness compared with the LBW and EBW joints. The resultant tensile and impact properties of the welded joints were correlated with the weld metal microstructures.
基金financially supported by the NSFC-Guangdong Joint Foundation Key Project(No.U2001218)the KeyArea Research and Development Program of Guangdong Province(No.2020B090924002)+1 种基金the National Natural Science Foundation of China(Nos.51875215,81772428)the Ministry of Education Key Laboratory of High-Efficiency Near-Net-Shape Forming Technology and Equipment for Metal Materials Open Fund(No.2019005)。
文摘In order to study the effect of gas atmosphere on forming performance of laser powder bed fusion(LPBF),AlSi10 Mg alloy was prepared by direct forming and in situ laser remelting under the shielding gas of argon and nitrogen in this study,and its micro structure and properties were characterized and tested,respectively.The results show that the forming performance of AlSi10 Mg under nitrogen atmosphere is better than that of argon.Moreover,in situ laser remelting method can effectively enhance the relative density and mechanical properties of AlSi10 Mg,in which the densification is increased to 99.5%.In terms of mechanical properties,after in situ remelting,ultimate tensile strength under argon protection increased from444.85±8.73 to 489.45±3.20 MPa,and that under nitrogen protection increased from 459.21±13.77 to 500.14±5.15 MPa.In addition,the elongation is nearly doubled and the micro-Vickers hardness is increased by 20%.The research results provide a new regulation control method for the customization of AlSi10 Mg properties fabricated by LPBF.