为解决大口径管道焊接预热不均匀的问题,提高焊接预热效率和预热质量,提出一种适用于大口径管道的智能预热机械设备,通过大开口C型夹具和基于模糊比例-积分-微分(Proportional Integral Differential,PID)的温度闭环控制方案,均匀预热...为解决大口径管道焊接预热不均匀的问题,提高焊接预热效率和预热质量,提出一种适用于大口径管道的智能预热机械设备,通过大开口C型夹具和基于模糊比例-积分-微分(Proportional Integral Differential,PID)的温度闭环控制方案,均匀预热大开口管道。试验结果表明:该设备具有良好的预热温度均匀性和预热温度控制精度,温度标准偏差仅为±1.8 ℃,最大温差不超过4.5 ℃,可用于大口径管道的焊接预热。展开更多
Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mec...Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mechanism of the joints obtained using three different rotation speeds were studied.High-performance FSLW Mg/Ti dissimilar joints with maximum tensile shear strength of 593.3 N/mm were produced at 1180 r/min,and which was mainly attributed to ultrastrong reaction interlayer consisting of 125.9 nm thick(Mg_(2)Sn+Mg)transition layer and discontinuous(Ti_(6)Sn_(5)+Ti_(3)Al)IMCs layer with 6.58 nm thickness at the interface.The formation of the reaction interlayer was beneficial for high interfacial strength,resulting in significantly improving the joint strength.The fracture of all FSLW joints located on AZ31B Mg stirred zone adjacent to(Mg_(2)Sn+Mg)transition layer or along the crack propagation direction of the AZ31B/TC4 interface with different fracture mechanisms,and which could be consistent with interfacial microstructure.展开更多
A low rare-earth containing ZEK100-O magnesium alloy was welded to AA1230-clad high-strength AA2024-T3 aluminum alloy via solidstate ultrasonic spot welding(USW)to evaluate the microstructure,tensile lap shear strengt...A low rare-earth containing ZEK100-O magnesium alloy was welded to AA1230-clad high-strength AA2024-T3 aluminum alloy via solidstate ultrasonic spot welding(USW)to evaluate the microstructure,tensile lap shear strength,and fatigue properties.The tensile strength increased with increasing welding energy,peaked at a welding energy of 1000 J,and then decreased due to the formation of an increasingly thick diffusion layer mainly containing Al12Mg17intermetallic compound at higher energy levels.The peak tensile lap shear strength attained at 1000 J was attributed to the optimal inter-diffusion between the magnesium alloy and softer AA1230-clad Al layer along with the presence of‘fishhook'-like mechanical interlocks at the weld interface and the formation of an indistinguishable intermetallic layer.The dissimilar joints welded at 1000 J also exhibited a longer fatigue life than other Mg-Al dissimilar joints,suggesting the beneficial role of the softer clad layer with a better intermingling capacity during USW.While the transverse-through-thickness(TTT)failure mode prevailed at lower cyclic loading levels,interfacial failure was the predominant mode of fatigue failure at higher cyclic loads,where distinctive fatigue striations were also observed on the fracture surface of the softer clad Al layer.This was associated with the presence of opening stress and bending moment near the nugget edge despite the tension-tension lap shear cyclic loading applied.展开更多
The pre-weld heat treatment was carried out to obtain different initial microstructures of the GH4169 superalloy,and then Linear Friction Welding(LFW)was performed.The effect of the pre-weld heat treatment on the micr...The pre-weld heat treatment was carried out to obtain different initial microstructures of the GH4169 superalloy,and then Linear Friction Welding(LFW)was performed.The effect of the pre-weld heat treatment on the microstructure evolution and mechanical properties of the joint was analyzed,and the joint electrochemical corrosion behavior as well as the hot corrosion behavior was studied.The results show that the joint hardness of Base Metal(BM)increases after pre-weld heat treatment,and the strengthening phasesγ′andγ″further precipitate.However,the precipitation phases dissolve significantly in the Weld Zone(WZ)due to the thermal process of LFW.The corrosion resistance in BM is reduced after the pre-weld heat treatment,while it is similar in WZ with a slight decrease.The surface morphology of the BM and WZ can be generally divided into a loose and porous matrix and a scattered oxide particle layer after hot corrosion.The joint cross section exhibits a Cr-depleted zone with the diffusion of Cr to form an oxide film.The corrosion product mainly consists of Fe_(2)O_(3)/Fe_(3)O_(4) as the outer layer and Cr_(2)O_(3) as the inner layer.展开更多
The transient liquid-phase(TLP)diffusion bonding of GH5188 with a BNi-5 interlayer was focused on.Parameters were chosen and optimized for GH5188 alloy according to the TLP joining mechanism.The microstructure evoluti...The transient liquid-phase(TLP)diffusion bonding of GH5188 with a BNi-5 interlayer was focused on.Parameters were chosen and optimized for GH5188 alloy according to the TLP joining mechanism.The microstructure evolution and mechanical properties of the joints were studied.Results show that the relatively complete isothermal solidification zone(ISZ)ensures a reliable connection of the base metal(BM).Within the temperature range of 1110–1190°C,higher bonding temperatures can widen ISZ and promote joint composition homogenization,thus improving mechanical properties.However,the increase in precipitated phase has an adverse effect on the mechanical properties of the joint.The maximum shear strength,reaching 482 MPa,is achieved at 1130°C,representing 84.6%of BM strength.Within the pressure range of 5–15 MPa,both precipitated phases in adiabatic solidification zone(ASZ)and voids generated by partial melting increase.On the contrary,their sizes decrease significantly under higher bonding pressure,resulting in an upward trend in alloy mechanical properties.The maximum shear strength of 490 MPa is attained at a bonding pressure of 15 MPa.The joint exhibits a typical mixed fracture pattern,with the small brittle M_(23)C_(6) phase and voids significantly impacting mechanical properties.Nano-indentation tests indicate that ASZ is a potential source of cracks.展开更多
The impact of casting defects on the weldability of K4951 superalloy was investigated using tungsten inert gas(TIG)welding.The as-cast K4951 superalloy samples with prefabricated U-shaped grooves of varying depths and...The impact of casting defects on the weldability of K4951 superalloy was investigated using tungsten inert gas(TIG)welding.The as-cast K4951 superalloy samples with prefabricated U-shaped grooves of varying depths and widths were TIG welded,and the microstructures,cracks morphology,and precipitated phases were analyzed using optical microscope,scanning electron microscope,transmission electron microscope,and energy dispersive X-ray spectrometer.The results reveal that the dimensions of casting defects significantly affect the weldability of K4951.Deep defects(greater than 2 mm)lead to rapid crack propagation,while wider defects can moderate the propagation process of cracks.Elemental segregation and the formation of precipitated phases,such as MC carbides,are observed in the fusion zone,contributing to welding cracks.An optimal groove aspect ratio(depth-to-width)between 0.2 and 0.5 minimizes crack formation tendency and enhances tensile strength,resulting in a mixed brittle-ductile fracture mode of joint after high-temperature tensile testing.展开更多
文摘为解决大口径管道焊接预热不均匀的问题,提高焊接预热效率和预热质量,提出一种适用于大口径管道的智能预热机械设备,通过大开口C型夹具和基于模糊比例-积分-微分(Proportional Integral Differential,PID)的温度闭环控制方案,均匀预热大开口管道。试验结果表明:该设备具有良好的预热温度均匀性和预热温度控制精度,温度标准偏差仅为±1.8 ℃,最大温差不超过4.5 ℃,可用于大口径管道的焊接预热。
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.52005240,52164045)Young Talent Program of Major Disciplines of Academic and Technical Leaders in Jiangxi Province(No.20212BCJ23028)Outstanding Youth Foundation in Jiangxi Province(No.20224ACB214012).
文摘Friction stir lap welding(FSLW)was adopted to join successfully dissimilar AZ31B Mg alloy and TC4 Ti alloy with Sn foil addition of 30μm thickness.Interfacial microstructure,tensile shear performances and bonding mechanism of the joints obtained using three different rotation speeds were studied.High-performance FSLW Mg/Ti dissimilar joints with maximum tensile shear strength of 593.3 N/mm were produced at 1180 r/min,and which was mainly attributed to ultrastrong reaction interlayer consisting of 125.9 nm thick(Mg_(2)Sn+Mg)transition layer and discontinuous(Ti_(6)Sn_(5)+Ti_(3)Al)IMCs layer with 6.58 nm thickness at the interface.The formation of the reaction interlayer was beneficial for high interfacial strength,resulting in significantly improving the joint strength.The fracture of all FSLW joints located on AZ31B Mg stirred zone adjacent to(Mg_(2)Sn+Mg)transition layer or along the crack propagation direction of the AZ31B/TC4 interface with different fracture mechanisms,and which could be consistent with interfacial microstructure.
基金the National Natural Science Foundation of China(Grant No.51971183)supported by OU(Osaka University,Japan)program for multilateral international collaboration research in joining and welding。
文摘A low rare-earth containing ZEK100-O magnesium alloy was welded to AA1230-clad high-strength AA2024-T3 aluminum alloy via solidstate ultrasonic spot welding(USW)to evaluate the microstructure,tensile lap shear strength,and fatigue properties.The tensile strength increased with increasing welding energy,peaked at a welding energy of 1000 J,and then decreased due to the formation of an increasingly thick diffusion layer mainly containing Al12Mg17intermetallic compound at higher energy levels.The peak tensile lap shear strength attained at 1000 J was attributed to the optimal inter-diffusion between the magnesium alloy and softer AA1230-clad Al layer along with the presence of‘fishhook'-like mechanical interlocks at the weld interface and the formation of an indistinguishable intermetallic layer.The dissimilar joints welded at 1000 J also exhibited a longer fatigue life than other Mg-Al dissimilar joints,suggesting the beneficial role of the softer clad layer with a better intermingling capacity during USW.While the transverse-through-thickness(TTT)failure mode prevailed at lower cyclic loading levels,interfacial failure was the predominant mode of fatigue failure at higher cyclic loads,where distinctive fatigue striations were also observed on the fracture surface of the softer clad Al layer.This was associated with the presence of opening stress and bending moment near the nugget edge despite the tension-tension lap shear cyclic loading applied.
基金supported by the National Natural Science Foundation of China(Nos.52074228,52305420 and 51875470)the Practice and Innovation Funds for Graduate Students of Northwestern Polytechnical University,China(No.PF2024053)the Xi’an Beilin District Science and Technology Planning Project,China(No.GX2349).
文摘The pre-weld heat treatment was carried out to obtain different initial microstructures of the GH4169 superalloy,and then Linear Friction Welding(LFW)was performed.The effect of the pre-weld heat treatment on the microstructure evolution and mechanical properties of the joint was analyzed,and the joint electrochemical corrosion behavior as well as the hot corrosion behavior was studied.The results show that the joint hardness of Base Metal(BM)increases after pre-weld heat treatment,and the strengthening phasesγ′andγ″further precipitate.However,the precipitation phases dissolve significantly in the Weld Zone(WZ)due to the thermal process of LFW.The corrosion resistance in BM is reduced after the pre-weld heat treatment,while it is similar in WZ with a slight decrease.The surface morphology of the BM and WZ can be generally divided into a loose and porous matrix and a scattered oxide particle layer after hot corrosion.The joint cross section exhibits a Cr-depleted zone with the diffusion of Cr to form an oxide film.The corrosion product mainly consists of Fe_(2)O_(3)/Fe_(3)O_(4) as the outer layer and Cr_(2)O_(3) as the inner layer.
基金National Natural Science Foundation of China(52075449,5197052086)。
文摘The transient liquid-phase(TLP)diffusion bonding of GH5188 with a BNi-5 interlayer was focused on.Parameters were chosen and optimized for GH5188 alloy according to the TLP joining mechanism.The microstructure evolution and mechanical properties of the joints were studied.Results show that the relatively complete isothermal solidification zone(ISZ)ensures a reliable connection of the base metal(BM).Within the temperature range of 1110–1190°C,higher bonding temperatures can widen ISZ and promote joint composition homogenization,thus improving mechanical properties.However,the increase in precipitated phase has an adverse effect on the mechanical properties of the joint.The maximum shear strength,reaching 482 MPa,is achieved at 1130°C,representing 84.6%of BM strength.Within the pressure range of 5–15 MPa,both precipitated phases in adiabatic solidification zone(ASZ)and voids generated by partial melting increase.On the contrary,their sizes decrease significantly under higher bonding pressure,resulting in an upward trend in alloy mechanical properties.The maximum shear strength of 490 MPa is attained at a bonding pressure of 15 MPa.The joint exhibits a typical mixed fracture pattern,with the small brittle M_(23)C_(6) phase and voids significantly impacting mechanical properties.Nano-indentation tests indicate that ASZ is a potential source of cracks.
基金National Natural Science Foundation of China(52201054,52175368)National Science and Technology Major Projects(J2019-VI-0018-0133)+2 种基金Liaoning Provincial Science and Technology Program(2023-BS-019,2023-MS-020)National Key R&D Program of China(2021YFB3700401)Key Specialized Research and Development Break-Through-Unveiling and Commanding the Special Project Program in Liaoning Province(2021JH15)。
文摘The impact of casting defects on the weldability of K4951 superalloy was investigated using tungsten inert gas(TIG)welding.The as-cast K4951 superalloy samples with prefabricated U-shaped grooves of varying depths and widths were TIG welded,and the microstructures,cracks morphology,and precipitated phases were analyzed using optical microscope,scanning electron microscope,transmission electron microscope,and energy dispersive X-ray spectrometer.The results reveal that the dimensions of casting defects significantly affect the weldability of K4951.Deep defects(greater than 2 mm)lead to rapid crack propagation,while wider defects can moderate the propagation process of cracks.Elemental segregation and the formation of precipitated phases,such as MC carbides,are observed in the fusion zone,contributing to welding cracks.An optimal groove aspect ratio(depth-to-width)between 0.2 and 0.5 minimizes crack formation tendency and enhances tensile strength,resulting in a mixed brittle-ductile fracture mode of joint after high-temperature tensile testing.
