In order to address the urgent demand for lightweight components in the aerospace,a laser-arc hybrid additive manufacturing(LAHAM)is innovatively applied to the Mg-Gd-Y-Zr alloy in this study.The results show that com...In order to address the urgent demand for lightweight components in the aerospace,a laser-arc hybrid additive manufacturing(LAHAM)is innovatively applied to the Mg-Gd-Y-Zr alloy in this study.The results show that compared with wire arc additive manufacturing(WAAM),the grain size and texture strength of LAHAM were reduced by about 26% and 27% respectively.The β phase at grain boundaries are effectively mitigated.In LAHAM,the nanoscale β phase(Mg_(24)(Gd,Y)_(5)+Mg_(5)(Gd,Y))and β_(1) phase(Mg_(3)(Gd,Y))were uniformly distributed in the grain boundary.There were only nanoscale β phase distributed around the enriched second phase in WAAM.The size and type of nanoparticles directly affect the mechanical properties of alloys.The tensile strength and yield strength of WAAM specimen were about 228 MPa,152 MPa.Compared with WAAM,the tensile strength and yield strength of LAHAM were increased by about 12% and 15%,reaching 254 MPa and 175 MPa.The contribution of precipitation strengthening is about 42%.This study provides a new perspective for the systematic application and fabrication of Mg-Gd-Y-Zr alloy.展开更多
A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of ...A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of shielding gases with varying He-Ar ratios,and the coupling between arc plasma and laser-induced metal plume.The accuracy of the model is validated using a high-speed camera.The effects of varying He contents in the shielding gas on both the temperature and flow velocity of hybrid plasma,as well as the distribu-tion of laser-induced metal vapor mass,were investigated separately.The maximum temperature and size of arc plasma decrease as the He volume ratio increases,the arc distribution becomes more concentrated,and its flow velocity initially decreases and then sharply increases.At high helium content,both the flow velocity of hybrid plasma and metal vapor are high,the metal vapor is con-centrated on the right side of keyhole,and its flow appears chaotic.The flow state of arc plasma is most stable when the shielding gas consists of 50%He+50%Ar.展开更多
Wire-fed laser-arc directed energy deposition(Wire-fed LA-DED)Technol.improves production speed while maintaining high quality and is particularly suited for manufacturing large,complex aluminum or titanium alloy comp...Wire-fed laser-arc directed energy deposition(Wire-fed LA-DED)Technol.improves production speed while maintaining high quality and is particularly suited for manufacturing large,complex aluminum or titanium alloy components.The geometry of the weld bead(height and width)is influenced by multiple intricate parameters and variables during the manufacturing process.Accurately predicting the weld bead shape enables precise control over the surface flatness of the part,helping to prevent defects such as lack of fusion.This significantly reduces dimensional redundancy,enhances printing efficiency,and optimizes material usage.In this study,a quadratic regression prediction model for weld bead geometry was developed using the response surface methodology(RSM),with predictions generated through several machine learning models.These models included the back-propagation neural network(BPNN),support vector regression(SVR),multi-output support vector regression(MOSVR),extreme learning machine(ELM),and a differential evolution-optimized MOSVR(DE-MOSVR)model.Grid search and cross-validation techniques were utilized to identify the optimal parameters for each model to achieve the best predictive performance.A comparison of these models was conducted,followed by an evaluation of their generalization capabilities using an additional 20 sets of test data.The most accurate predictive model was selected based on a comprehensive assessment.The results showed that the DE-MOSVR model outperformed the others,achieving mean squared error,root mean squared error,mean absolute error,and R^(2) values for width(height)predictions of 0.0411(0.0041),0.2028(0.0639),0.1671(0.0550),and 0.9434(0.9433),respectively.It demonstrated the smallest deviation in the validation set,with mean deviations of 1.97% and 1.68%,respectively.The model we developed was validated through the production of prototype parts,providing valuable reference and guidance for predicting and modeling weld bead morphology in the Wire-fed LA-DED process.展开更多
In recent years, the research on pipeline laser-arc hybrid welding technology has been the important and difficult in the field of welding all over the world. China Petroleum Pipeline Research Institute Co. Ltd. has f...In recent years, the research on pipeline laser-arc hybrid welding technology has been the important and difficult in the field of welding all over the world. China Petroleum Pipeline Research Institute Co. Ltd. has firstly developed pipeline laser-arc hybrid welding system in China, and executed the welding tests based on X70/X80 steel. Preliminary experiment results showed that hybrid welding could meet the requirements of related standards such as API1104,ASME,etc., the mechanical properties of girth seam are qualified in the case that there were no internal defects. With the development of high-power fiber laser and the continuous improvement of welding equipment, laser-arc hybrid welding technology for pipeline field welding will be available soon.展开更多
Laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of welding parameters on weld formation,microstructure homogeneity and mechanical properties were investigated.The results showed that lase...Laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of welding parameters on weld formation,microstructure homogeneity and mechanical properties were investigated.The results showed that laser-arc hybrid welding was beneficial to improve the weld formation of magnesium alloy by inhibiting the defect of undercut and pores.The weld microstructure was mainly columnar grains neighboring the fusion line and equiaxed grains at the weld center.It was interesting that the grain size at the upper arc zone was smaller than that at the lower laser zone,with the difference mainly affected by laser power rather than welding current and welding speed.The welding parameters were optimized as laser power of 3.5 kW,welding current of 100 A and welding speed of 1.5 m/min.In this case,the weld was free of undercut and pores,and the tensile strength and elongation rate reached 252 MPa and 11.2%,respectively.Finally,the microstructure homogeneity was illustrated according to the heat distribution,and the evolution law of tensile properties was discussed basing on the weld formation and microstructure characteristics.展开更多
Recently,rapid and cost-effective additive manufacturing solutions for lightweight aluminum alloys with excellent high-temperature mechanical properties have been increasingly in demand.In this study,we combined laser...Recently,rapid and cost-effective additive manufacturing solutions for lightweight aluminum alloys with excellent high-temperature mechanical properties have been increasingly in demand.In this study,we combined laser-arc hybrid additive manufacturing with solution and artificial aging treatments to achieve Al-Zn-Mg-Cu alloy with favorable high-temperature strength via microstructure control.Hydrogen pores became the major defect in the as-deposited and heat-treated specimens.The continuous distribution of eutectics with hard-brittle characteristics at the grain boundaries was destructed following heat treat-ment.High-densityηprecipitates were uniformly dispersed in the heat-treated Al-Zn-Mg-Cu alloy,whereas appeared coarsened and dissolved at 473 K,owing to the rapid diffusion of Zn and Mg.The average 0.2%yield strength(318±16 MPa)and ultimate tensile strength(362±20 MPa)at 473 K af-ter heat treatment were enhanced by approximately 58%and 51%,respectively,compared to those of the as-deposited specimen.In addition,theηprecipitates contributed to lattice distortions and strain fields,which prevented dislocation motion and increased slip deformation resistance at high temper-atures.The as-deposited specimen exhibited intergranular fracture at 473 K,with cracks preferring to propagate along the aggregated eutectics.However,crack propagation proceeded in the sections with more pores in the heat-treated specimen.Our approach may provide a valid option for achieving alu-minum alloys with excellent high-temperature mechanical properties.展开更多
Aluminum alloy 6061 and high-strength steel Q460 were joined by laser-arc-adhesive hybrid welding technology successfully.A Cu alloy interlayer was added between Al alloy and high-strength steel.The effect of the adhe...Aluminum alloy 6061 and high-strength steel Q460 were joined by laser-arc-adhesive hybrid welding technology successfully.A Cu alloy interlayer was added between Al alloy and high-strength steel.The effect of the adhesive on laser-arc-adhesive hybrid welding of Al alloy to high-strength steel was discussed.The optical microscope,scanning electron microscope and electron probe micro-analysis were applied to observe the microstructural evolution and phase transition at Al-Fe interface of laser-arc-adhesive hybrid welded joints.The results showed the maximum tensile shear strength of the joint without adhesive was 256 MPa.After adding adhesive,the maximum tensile shear strength reached 282 MPa.The combination of the mechanical bonding and the metallurgical effect could improve the mechanical performances.The shape of the joint in Al alloy changed into a canine-like morphology.There was no porosity in welds because the molten pool of Al alloy and the special keyhole phenomenon of laser welding provided a channel for the decomposed gas to escape from fusion zone.展开更多
Oscillating laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of beam oscillation parameters on pore inhibition,microstructure,grain boundary characteristics and tensile properties were inv...Oscillating laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of beam oscillation parameters on pore inhibition,microstructure,grain boundary characteristics and tensile properties were investigated.The results showed that the pore formation can be inhibited with oscillating frequency higher than 75 Hz and radius smaller than 0.5 mm.The columnar grains neighboring the fusion line can be broken by the beam oscillation behavior,while the grain growth was promoted with the increase of frequency or radius.It should be noted that the coincidence site lattice(CSL)boundaries were mainlyΣ13b andΣ29 boundaries,which were contributed by{10■2}tensile twins and{11■2}compression twins,respectively.The total fraction of CSL boundaries reached maximum at radius of 0.25 mm and frequency of 75 Hz,which was also confirmed as the optimized parameters.In this case,the elongation rate increased up to 13.2%,12.8%higher than that of the weld without beam oscillation.Finally,the pore formation and inhibition mechanisms were illustrated according to the state of melt flow and keyhole formation,the abnormal growth was discussed basing on secondary recrystallization,and the relationship among the pore formation,grain size,boundary characteristics and weld toughness were finally established.展开更多
Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear...Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear-resistant steel is proposed. The proposed model considers convection, radiation, molten pool flow, and heat conduction effect on temperature. A comparison of the simulation and actual welding test results confirms the reliability of the model. This welding heat-process model can provide the cooling rate at any position in the heat affected zone （HAZ） and can be used as a reference for the analysis of material properties and for process optimization.展开更多
Laser-arc hybrid welding has the characteristics of optimal surface formation and greater penetration;it is extensively used in the welding of plates of medium thickness.However, for hybrid welding of lasers, the weld...Laser-arc hybrid welding has the characteristics of optimal surface formation and greater penetration;it is extensively used in the welding of plates of medium thickness.However, for hybrid welding of lasers, the welding seam cooling rate is rapid;thus, the welding seam has a higher tendency to significantly harden, which has a negative impact on the weld quality of the high-strength low-alloy(HSLA) steel plates of medium thickness.In this study, laser-arc hybrid welding is performed on the BG890 QL HSLA steel produced by Baoshan Iron & Steel Co.,Ltd.,and the quenching tendency of the welded structure is examined.The results demonstrate that the specific growth direction of the columnar crystal structure of the laser-arc hybrid welded joint is obvious.However, at the center and top of the welded seam, there are equiaxed crystals.The impact properties at room temperature and-40 ℃ of the weld area are 58.0 J and 40.0 J,respectively, and those of the heat-affected zone(HAZ) are 147.0 J and 66.5 J,respectively.The impact performance can meet these requirements.Laser-arc hybrid welding of HSLA steel can yield strong and durable welds and the HAZ structure to meet the requirements of engineering applications.展开更多
The corrosion resistance of base metal,laser-arc hybrid welded AZ31B magnesium alloys with and without addition of carbon nanotubes(CNTs)was compared.The corrosion behaviors and the underlying improvement mechanism of...The corrosion resistance of base metal,laser-arc hybrid welded AZ31B magnesium alloys with and without addition of carbon nanotubes(CNTs)was compared.The corrosion behaviors and the underlying improvement mechanism of CNTs were systematically investigated.The introduction of CNTs effectively refined the grains,weakened the texture and enhanced the microstructure homogeneity of the weld,which contributed to the enhancement of corrosion resistance.Specifically,the corrosion rates of hydrogen evolution and weight loss of weld decreased by>30%after the addition of CNTs,and the corrosion products were denser due to the formation of Al_(2)O_(3)passive film.The corrosion current density and polarization resistance of weld with addition of CNTs were 1.220μA/cm^(2)and 7155·cm^(2),respectively,in contrast to 2.480μA/cm^(2)and approximately 269.5·cm^(2)for the weld without CNTs.Besides,the content of precipitates in the weld increased from 0.60%to 1.76%after the addition of CNTs,which can release Al^(3+)ions,promoting the formation of a dense Al_(2)O_(3)film that serves to protect the metal matrix from further degradation.展开更多
The lamellar layer of intermetallic compounds(IMCs)was adversely affected the performance of welding-brazing joints in Al/steel dissimilar metals.In this study,a short fiber-like surface morphology was fabricated on t...The lamellar layer of intermetallic compounds(IMCs)was adversely affected the performance of welding-brazing joints in Al/steel dissimilar metals.In this study,a short fiber-like surface morphology was fabricated on the butt surface of Q235 steel via laser.The interaction behavior between the short fibers and the molten pool was captured using a high-speed camera.Laser-arc hybrid welding-brazing was then employed to join Al(6061-T6)to the steel.This process successfully created a short fiber-like interface structure at the joint.The relationship between microstructure and mechanical properties was investigated,compared with Al/bare steel(ABS)joint.The research results indicated that the IMCs layer consisted of FeAl_(3)and Fe_(2)Al_(5).The interface strength of the Al/short fiber-like surface structural steel(ASFSSS)joint reached 153.2 MPa,an 82.2%increase compared to the ABS joint,which reached 84.1 MPa.When the ASFSSS joints without the reinforcement were bent to 58.2°and 25.2°in the longitudinal and transverse direction,respectively,they remained intact.However,cracks were discovered when the bending angle of the ABS reached 39.1°and 0°in the two directions.Numerical simulation revealed that the short fiber-like interface structure significantly reduced residual stress and improved the stress distribution in the weld,thereby enhancing the strength and toughness of Al/steel dissimilar joints.The crack propagation path in the ASFSSS joint was deflected into the weld when it encountered short fibers,and the fracture morphology presented the characteristic of ductile-brittle mixed fracture.展开更多
基金the financial support from the National Key Research and Development Program(No.2023YFB4606004 and No 2023YFB4606002)the Fundamental Research Funds for the Central University(No.DUT21YG116).
文摘In order to address the urgent demand for lightweight components in the aerospace,a laser-arc hybrid additive manufacturing(LAHAM)is innovatively applied to the Mg-Gd-Y-Zr alloy in this study.The results show that compared with wire arc additive manufacturing(WAAM),the grain size and texture strength of LAHAM were reduced by about 26% and 27% respectively.The β phase at grain boundaries are effectively mitigated.In LAHAM,the nanoscale β phase(Mg_(24)(Gd,Y)_(5)+Mg_(5)(Gd,Y))and β_(1) phase(Mg_(3)(Gd,Y))were uniformly distributed in the grain boundary.There were only nanoscale β phase distributed around the enriched second phase in WAAM.The size and type of nanoparticles directly affect the mechanical properties of alloys.The tensile strength and yield strength of WAAM specimen were about 228 MPa,152 MPa.Compared with WAAM,the tensile strength and yield strength of LAHAM were increased by about 12% and 15%,reaching 254 MPa and 175 MPa.The contribution of precipitation strengthening is about 42%.This study provides a new perspective for the systematic application and fabrication of Mg-Gd-Y-Zr alloy.
基金supported by the National Natural Science Foundation of China(Grant No.52375340,51975263,52405366).
文摘A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of shielding gases with varying He-Ar ratios,and the coupling between arc plasma and laser-induced metal plume.The accuracy of the model is validated using a high-speed camera.The effects of varying He contents in the shielding gas on both the temperature and flow velocity of hybrid plasma,as well as the distribu-tion of laser-induced metal vapor mass,were investigated separately.The maximum temperature and size of arc plasma decrease as the He volume ratio increases,the arc distribution becomes more concentrated,and its flow velocity initially decreases and then sharply increases.At high helium content,both the flow velocity of hybrid plasma and metal vapor are high,the metal vapor is con-centrated on the right side of keyhole,and its flow appears chaotic.The flow state of arc plasma is most stable when the shielding gas consists of 50%He+50%Ar.
基金supported by Natural Science Foundation of Shandong Province(Grant No.ZR202212010161)Natural Science Foundation of Qingdao(Grant No.23-2-1-83-zyyd-jch)+1 种基金Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515110116)the National Natural Science Foundation of China(Grant No.52405359).
文摘Wire-fed laser-arc directed energy deposition(Wire-fed LA-DED)Technol.improves production speed while maintaining high quality and is particularly suited for manufacturing large,complex aluminum or titanium alloy components.The geometry of the weld bead(height and width)is influenced by multiple intricate parameters and variables during the manufacturing process.Accurately predicting the weld bead shape enables precise control over the surface flatness of the part,helping to prevent defects such as lack of fusion.This significantly reduces dimensional redundancy,enhances printing efficiency,and optimizes material usage.In this study,a quadratic regression prediction model for weld bead geometry was developed using the response surface methodology(RSM),with predictions generated through several machine learning models.These models included the back-propagation neural network(BPNN),support vector regression(SVR),multi-output support vector regression(MOSVR),extreme learning machine(ELM),and a differential evolution-optimized MOSVR(DE-MOSVR)model.Grid search and cross-validation techniques were utilized to identify the optimal parameters for each model to achieve the best predictive performance.A comparison of these models was conducted,followed by an evaluation of their generalization capabilities using an additional 20 sets of test data.The most accurate predictive model was selected based on a comprehensive assessment.The results showed that the DE-MOSVR model outperformed the others,achieving mean squared error,root mean squared error,mean absolute error,and R^(2) values for width(height)predictions of 0.0411(0.0041),0.2028(0.0639),0.1671(0.0550),and 0.9434(0.9433),respectively.It demonstrated the smallest deviation in the validation set,with mean deviations of 1.97% and 1.68%,respectively.The model we developed was validated through the production of prototype parts,providing valuable reference and guidance for predicting and modeling weld bead morphology in the Wire-fed LA-DED process.
文摘In recent years, the research on pipeline laser-arc hybrid welding technology has been the important and difficult in the field of welding all over the world. China Petroleum Pipeline Research Institute Co. Ltd. has firstly developed pipeline laser-arc hybrid welding system in China, and executed the welding tests based on X70/X80 steel. Preliminary experiment results showed that hybrid welding could meet the requirements of related standards such as API1104,ASME,etc., the mechanical properties of girth seam are qualified in the case that there were no internal defects. With the development of high-power fiber laser and the continuous improvement of welding equipment, laser-arc hybrid welding technology for pipeline field welding will be available soon.
基金financially supported by the National Natural Science Foundation of China(grant nos.51905391,52025052 and 51975405)。
文摘Laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of welding parameters on weld formation,microstructure homogeneity and mechanical properties were investigated.The results showed that laser-arc hybrid welding was beneficial to improve the weld formation of magnesium alloy by inhibiting the defect of undercut and pores.The weld microstructure was mainly columnar grains neighboring the fusion line and equiaxed grains at the weld center.It was interesting that the grain size at the upper arc zone was smaller than that at the lower laser zone,with the difference mainly affected by laser power rather than welding current and welding speed.The welding parameters were optimized as laser power of 3.5 kW,welding current of 100 A and welding speed of 1.5 m/min.In this case,the weld was free of undercut and pores,and the tensile strength and elongation rate reached 252 MPa and 11.2%,respectively.Finally,the microstructure homogeneity was illustrated according to the heat distribution,and the evolution law of tensile properties was discussed basing on the weld formation and microstructure characteristics.
基金support from the National Natural Science Foundation of China(No.52175291)the Natural Science Foundation of Liaoning Province(No.2022-YGJC-22).
文摘Recently,rapid and cost-effective additive manufacturing solutions for lightweight aluminum alloys with excellent high-temperature mechanical properties have been increasingly in demand.In this study,we combined laser-arc hybrid additive manufacturing with solution and artificial aging treatments to achieve Al-Zn-Mg-Cu alloy with favorable high-temperature strength via microstructure control.Hydrogen pores became the major defect in the as-deposited and heat-treated specimens.The continuous distribution of eutectics with hard-brittle characteristics at the grain boundaries was destructed following heat treat-ment.High-densityηprecipitates were uniformly dispersed in the heat-treated Al-Zn-Mg-Cu alloy,whereas appeared coarsened and dissolved at 473 K,owing to the rapid diffusion of Zn and Mg.The average 0.2%yield strength(318±16 MPa)and ultimate tensile strength(362±20 MPa)at 473 K af-ter heat treatment were enhanced by approximately 58%and 51%,respectively,compared to those of the as-deposited specimen.In addition,theηprecipitates contributed to lattice distortions and strain fields,which prevented dislocation motion and increased slip deformation resistance at high temper-atures.The as-deposited specimen exhibited intergranular fracture at 473 K,with cracks preferring to propagate along the aggregated eutectics.However,crack propagation proceeded in the sections with more pores in the heat-treated specimen.Our approach may provide a valid option for achieving alu-minum alloys with excellent high-temperature mechanical properties.
基金This work was supported by the National Key R&D Program of China(2018YFB1107900)the National Natural Science Foundation of China(Grant Nos.U1764251 and 51975090).
文摘Aluminum alloy 6061 and high-strength steel Q460 were joined by laser-arc-adhesive hybrid welding technology successfully.A Cu alloy interlayer was added between Al alloy and high-strength steel.The effect of the adhesive on laser-arc-adhesive hybrid welding of Al alloy to high-strength steel was discussed.The optical microscope,scanning electron microscope and electron probe micro-analysis were applied to observe the microstructural evolution and phase transition at Al-Fe interface of laser-arc-adhesive hybrid welded joints.The results showed the maximum tensile shear strength of the joint without adhesive was 256 MPa.After adding adhesive,the maximum tensile shear strength reached 282 MPa.The combination of the mechanical bonding and the metallurgical effect could improve the mechanical performances.The shape of the joint in Al alloy changed into a canine-like morphology.There was no porosity in welds because the molten pool of Al alloy and the special keyhole phenomenon of laser welding provided a channel for the decomposed gas to escape from fusion zone.
基金financially supported by the National Natural Science Foundation of China(grant nos.51905391,52025052 and 51975405).
文摘Oscillating laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of beam oscillation parameters on pore inhibition,microstructure,grain boundary characteristics and tensile properties were investigated.The results showed that the pore formation can be inhibited with oscillating frequency higher than 75 Hz and radius smaller than 0.5 mm.The columnar grains neighboring the fusion line can be broken by the beam oscillation behavior,while the grain growth was promoted with the increase of frequency or radius.It should be noted that the coincidence site lattice(CSL)boundaries were mainlyΣ13b andΣ29 boundaries,which were contributed by{10■2}tensile twins and{11■2}compression twins,respectively.The total fraction of CSL boundaries reached maximum at radius of 0.25 mm and frequency of 75 Hz,which was also confirmed as the optimized parameters.In this case,the elongation rate increased up to 13.2%,12.8%higher than that of the weld without beam oscillation.Finally,the pore formation and inhibition mechanisms were illustrated according to the state of melt flow and keyhole formation,the abnormal growth was discussed basing on secondary recrystallization,and the relationship among the pore formation,grain size,boundary characteristics and weld toughness were finally established.
文摘Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear-resistant steel is proposed. The proposed model considers convection, radiation, molten pool flow, and heat conduction effect on temperature. A comparison of the simulation and actual welding test results confirms the reliability of the model. This welding heat-process model can provide the cooling rate at any position in the heat affected zone （HAZ） and can be used as a reference for the analysis of material properties and for process optimization.
文摘Laser-arc hybrid welding has the characteristics of optimal surface formation and greater penetration;it is extensively used in the welding of plates of medium thickness.However, for hybrid welding of lasers, the welding seam cooling rate is rapid;thus, the welding seam has a higher tendency to significantly harden, which has a negative impact on the weld quality of the high-strength low-alloy(HSLA) steel plates of medium thickness.In this study, laser-arc hybrid welding is performed on the BG890 QL HSLA steel produced by Baoshan Iron & Steel Co.,Ltd.,and the quenching tendency of the welded structure is examined.The results demonstrate that the specific growth direction of the columnar crystal structure of the laser-arc hybrid welded joint is obvious.However, at the center and top of the welded seam, there are equiaxed crystals.The impact properties at room temperature and-40 ℃ of the weld area are 58.0 J and 40.0 J,respectively, and those of the heat-affected zone(HAZ) are 147.0 J and 66.5 J,respectively.The impact performance can meet these requirements.Laser-arc hybrid welding of HSLA steel can yield strong and durable welds and the HAZ structure to meet the requirements of engineering applications.
基金supported by the National Natural Science Foundation of China(grant nos.52275364 and 52025052)。
文摘The corrosion resistance of base metal,laser-arc hybrid welded AZ31B magnesium alloys with and without addition of carbon nanotubes(CNTs)was compared.The corrosion behaviors and the underlying improvement mechanism of CNTs were systematically investigated.The introduction of CNTs effectively refined the grains,weakened the texture and enhanced the microstructure homogeneity of the weld,which contributed to the enhancement of corrosion resistance.Specifically,the corrosion rates of hydrogen evolution and weight loss of weld decreased by>30%after the addition of CNTs,and the corrosion products were denser due to the formation of Al_(2)O_(3)passive film.The corrosion current density and polarization resistance of weld with addition of CNTs were 1.220μA/cm^(2)and 7155·cm^(2),respectively,in contrast to 2.480μA/cm^(2)and approximately 269.5·cm^(2)for the weld without CNTs.Besides,the content of precipitates in the weld increased from 0.60%to 1.76%after the addition of CNTs,which can release Al^(3+)ions,promoting the formation of a dense Al_(2)O_(3)film that serves to protect the metal matrix from further degradation.
基金supported by the National Natural Science Foundation of China(No.52275306)the Beijing Municipal Natural Science Foundation(No.3232021).
文摘The lamellar layer of intermetallic compounds(IMCs)was adversely affected the performance of welding-brazing joints in Al/steel dissimilar metals.In this study,a short fiber-like surface morphology was fabricated on the butt surface of Q235 steel via laser.The interaction behavior between the short fibers and the molten pool was captured using a high-speed camera.Laser-arc hybrid welding-brazing was then employed to join Al(6061-T6)to the steel.This process successfully created a short fiber-like interface structure at the joint.The relationship between microstructure and mechanical properties was investigated,compared with Al/bare steel(ABS)joint.The research results indicated that the IMCs layer consisted of FeAl_(3)and Fe_(2)Al_(5).The interface strength of the Al/short fiber-like surface structural steel(ASFSSS)joint reached 153.2 MPa,an 82.2%increase compared to the ABS joint,which reached 84.1 MPa.When the ASFSSS joints without the reinforcement were bent to 58.2°and 25.2°in the longitudinal and transverse direction,respectively,they remained intact.However,cracks were discovered when the bending angle of the ABS reached 39.1°and 0°in the two directions.Numerical simulation revealed that the short fiber-like interface structure significantly reduced residual stress and improved the stress distribution in the weld,thereby enhancing the strength and toughness of Al/steel dissimilar joints.The crack propagation path in the ASFSSS joint was deflected into the weld when it encountered short fibers,and the fracture morphology presented the characteristic of ductile-brittle mixed fracture.
