查看更多>>摘要：Laser oscillating welding of 2205 duplex stainless steel was performed using Ni interlayer as filler material.The influence of stirring effect caused by laser oscillating and Ni addition in the behavior of molten pool and the microstructure evolution was investigated.The results shows that Ni addition decreased the ratio of chromium equivalent and nickel equivalent in the molten pool and accelerated the austenitic transformation.The austenite/ferrite ratio was regulated,and the precipitation of nitrides was suppressed in the weld seam.The stirring effect caused by the oscillating beam facilitated the uniform distribution of Ni elements within the molten pool,promoting the formation of the homogeneous microstructures in the weld seam.With increasing the thickness of Ni interlayer,both the dimension and the peak temperature of molten pool decrease,further increasing the cooling rate and refining the grain size.When the thickness of Ni interlayer was 50 μm,the austenite/ferrite ratio in the weld seam was close to 1:1,and the grain size reached the minimum value.The tensile strength and ductility of the welded joint using Ni interlayer with thickness were 774 MPa and 25%,respectively,significantly improving the mechanical properties of 2205 duplex stainless steel joint welded without Ni addition.
查看更多>>摘要：Ti3SiC2 ceramic and SUS430 ferritic stainless steel were welded by the transient liquid phase(TLP)diffusion bonding method using an Al interlayer at 850-1050℃ in vacuum.The evolution of phase and morphology at the interface and bonding strength were systematically investigated.The results show that Ti3SiC2 and SUS430 were well bonded at 900-950℃.Three reaction zones were observed at the interface.At the joint interface area adjacent to alloy,the alloy completely reacted with liquid Al to form Al86Fe14.At Ti3SiC2/Al interface,Ti and Si diffused outward from Ti3SiC2 into the molten Al to form Fe3Al+Al5FeSi+TiAl3 zone.Adjacent to Ti3SiC2 matrix,Ti3Si(Al)C2+TiCx zone was formed by the loss of Si.The evolution mechanism of TLP-bonded joints was discussed based on the interface microstructure and product phases.In addition,the tensile strength of the joint increased with increasing bonding temperature.The corre-sponding maximum value of 59.7 MPa was obtained from SUS430/Al(10 μm)/Ti3SiC2 joint prepared at 950℃.
查看更多>>摘要：The lap joints of 6061-T6 aluminum alloy/Q235 steel were prepared by conventional friction stir welding and ultrasonic vibration enhanced friction stir welding.Firstly,the effect of ultrasonic vibration on the microstructure and properties of joints was analyzed,and then the optimization mechanism of ultrasonic vibration on failure load and corrosion resistance of joints was elucidated.The results indicated that ultrasonic vibration could significantly improve the quality of weld formation,expand the width of interface zone,change the shape of the''hook''structure,form a macro mechanical interlock at the joint interface,and effectively refine the grain structure on the steel side.In terms of the microstructure of the joints,additional ultrasonic energy can change the microstructure characteristics at the interface,and can improve the distribution characteristics of precipitates in the weld nugget zone,significantly reducing the number of intermetallic compounds generated across the interface of the retreating side and forming micro mechanical interlock on the advancing side of the interface.After ultrasonic treatment,the failure load of the aluminum/steel lap joint increased by 20.4%,and the corrosion resistance improved by 1.304 times.
查看更多>>摘要：5052 Al and carbon fiber-reinforced polyamide 6 composite(CF-PA6)were jointed via ultrasonic welding with the assistance of temperature compensation device.The effects of the ultrasonic welding time and temperature compensation on the microstructure and mechanical properties of the joints were investigated.Through analysis of the wettability and fluidity of the molten carbon fiber-reinforced thermoplastic composites(CFRTP),the bonding mechanism and failure path of Al/CFRTP were clarified.The results show that under the conditions of temperature compensation of 220℃ and welding time of 1500 ms,the joint strength of the two components reaches 2480.4 N,which is 813.6%higher than that of Al/CFRTP components obtained at room temperature.Overall,temperature compensation prolonged the wetting time of molten CFRTP on the aluminum alloy surface.When the fluidity and wettability were coordinated with each other,a high-quality joint was formed.In addition,the ultrasonic welding process of Al/CFRTP mainly relies on''physical adsorption,''''diffusion effect,''and''mechanical locking effect''to achieve sufficient bonding,and the effect of hydrogen bonding is weak.
查看更多>>摘要：The welding characteristics of 5052 aluminum alloy and Q235 low-carbon steel sheet were systematically studied by the refilled friction stir spot welding.The effects of rotation speed and pressure speed on weld forming,tensile strength,and welded joint structure were analyzed in different welding modes.The results indicated two different connection modes:the chimeric mode and the non-chimeric mode.The corresponding depression depth are 2 and 2.4 mm,respectively.In the non-chimeric connection mode,the steel/aluminum metallurgical interface is a smooth transition,the hook structure is obvious,and the welding mechanism mainly depends on the mutual diffusion between atoms.However,in the chimeric mode,a hook structure will be formed at the metallurgical interface of steel and aluminum.The connection mechanism is determined by mechanical interlocking and mutual diffusion.The maximum strength value is 7.48 kN in non-chimeric mode.At this time,the spindle speed is 1300 r/min and the pressure speed is 1 mm/s.There were two types of fractures:the button fracture mode and the peel fracture mode.
查看更多>>摘要：Based on the two-pass differential temperature rolling bonding method,the effects of prefabricated steel/aluminum composite panel temperature on interface characteristics and microstructure properties were investigated through exper-imental analysis and finite element simulations.When the temperature exceeds 400℃,the effective preparation of the steel-aluminum transition joint can be achieved,and with the increase in temperature,the interface shear and pull-off strength of the steel-aluminum transition joint exhibits an initial decrease followed by an increase.Both the interface shear and pull-off fractures are in 1060 aluminum matrix.As the temperature increases,the size of the average grain in 1060 aluminum matrix increases and then decreases.When the temperature reaches 550℃,the comprehensive performance of the prepared steel-aluminum transition joint is the best,with the interface shear strength of 77 MPa and the interface pull-off strength of 153 MPa,exceeding the bonding strength of the explosive compounding method.There are no pinholes,wrinkles,or cracks in the lateral bending matrix and the interface.
查看更多>>摘要：The contact-reactive brazing of Al0.3CoCrFeNi high-entropy alloys with a Nb interlayer was researched.The effects of Nb thickness and brazing temperature on the interfacial microstructure and mechanical properties of Al0.3CoCrFeNi joints were investigated.The results show that with Nb thickness increasing from 10 to 100 μm,the average width of Al0.3-CoCrFeNi joints is increased from 127 to 492 μm and the erosion volume of Al0.3CoCrFeNi base metals(BMs)by face-centered cubic-Nb eutectic liquid is enlarged accordingly.With increasing brazing temperature from 1280 to 1360℃,the intergranular penetration of eutectic liquid into Al0.3CoCrFeNi BMs becomes more severe and lamellar Laves phase is broken-up and spherized.The shear strength of joint is increased gradually from 374 to 486 MPa and then decreased to 475 MPa.The maximum shear strength value of 486 MPa is obtained when brazing at 1340℃ for 10 min,reaching about 78%of the shear strength of Al0.3CoCrFeNi BMs.Besides,the brazing mechanism was analyzed in details.
查看更多>>摘要：The diffusion processes in bicrystalline Cu/Al joints,characterized by typical high-angle grain boundaries(GBs),were investigated using molecular dynamics simulations.It was found that GBs facilitated the diffusion of both Cu and Al atoms,predominantly enhancing the migration of Cu atoms into Al matrix.According to mean squared displacement results,the movement of Al atoms within Al matrix was more vigorous than that of Cu atoms.The mechanisms of atomic rearrangement,dislocation movement,stacking fault formation,and dynamic recrystallization were analyzed.During the compression and initial welding stages,the mismatch in lattice constants and the twisting of grains initiated a squeeze-induced rearrangement of Al atoms at the interface,leading to the formation of dislocations and vacancies.During the advanced stages of welding,the plastic deformation primarily occurred within Al matrix,marked by the emergence of dislocations,stacking faults,and GB sliding.Particularly,the shearing effect during the ultrasonic welding process,combined with GB sliding,collectively induced grain recrystallization at the interface.Furthermore,the diffusion between Cu/Al joints could be enhanced by increasing the vibration frequency,due to a significant rise in the number of amorphous regions.
查看更多>>摘要：The electromigration reliability on Sn-10Bi solder joints is investigated and the performance is tried to be improved with trace Zn addition in solder by depressing the growth of interfacial intermetallic compounds(IMCs)under electromigration.The electromigration test was realized on Cu/solder/Cu linear specimens at a current density of 1.0×104 A/cm2 with different stressing time.It was found that Bi atoms in Cu/Sn-10Bi/Cu solder joint were driven towards anode side under current driving force and then accumulated at anode interface with current stressing time increasing.The thickness and growth rate of Cu6Sn5 IMCs at anode interface were obviously larger than those at cathode side due to polarity effect.The addition of 0.2 wt.%Zn inhibited the migration of Bi atoms during the electromigration process,and the composition of interfacial IMCs was transformed into Cu6(Sn,Zn)5,which played as a diffusion barrier to effectively reduce the asym-metric growth of IMCs and the consumption of Cu substrate during electromigation.
查看更多>>摘要：The dissimilar brazing of Nb521 niobium alloy to GH99 superalloy was achieved successfully using Ti-35Ni brazing filler under vacuum.The effects of brazing temperature and holding time were systematically analyzed on the interfacial microstructure evolution and mechanical properties of joints.The joints brazed at 1120℃ for 10 min exhibited a typical interfacial structure composed of Nb521/β-(Nb,Ti)+TiNi/TiNi+Ti2Ni/TiNi+TiNi3/Cr-rich TiNi/Ti-rich(Ni,Cr)ss/(Ni,Cr)ss/GH99.The findings indicated that as the brazing temperature or holding time increased,the presence of brittle Ti2Ni compounds decreased while the formation of TiNi3 gradually increased and tended to coarsen.The shear strength of joints exhibited variations corresponding to changes in interfacial brittle compound,and reached the highest value of 121 MPa at 1120℃ for 10 min.In the context of shear testing,all joints displayed clear brittle fracture patterns,with fractures predominantly occurring at the brittle compounds,namely,Ti2Ni and TiNi3 phases.
NETL
NSTL
万方数据