AA1060–DP600板材电磁脉冲连接工艺研究

目的基于平板线圈对AA1060–DP600板材电磁脉冲连接过程进行数值模拟与工艺实验,探索线圈匝数、搭接区宽度、搭接间隙和放电电压等4个参数对连接接头质量的影响。方法基于有限元分析软件(LS–DYNA),建立尺寸参数为80 mm×40 mm×1 mm的AA1060–DP600板材电磁脉冲连接有限元模型;基于平板线圈搭接实验装置进行工艺实验,采用电子万能实验机、金相显微镜对接头拉伸性能进行测试并观察其微观形貌,结合模拟与工艺实验的结果分析各个参数对接头质量的影响。结果随平板跑道线圈匝数由1匝增至6匝,飞板与基板碰撞速度先升后降,在3匝时达到最大值;搭接间隙过大(2.5 mm)或过小(1.5 mm)都会使碰撞速度下降,进而使接头强度下降;碰撞速度和接头强度与搭接区宽度和放电电压成正相关,放电电压在9 kV及以上时更易实现连接;连接接头界面总体趋于平直,部分区域出现小波峰大波长的波形。结论以拉伸性能最优为标准,最优的工艺参数为线圈匝数3匝、搭接间隙2 mm、搭接区宽度25 mm、放电电压11 kV,此条件下试件可承受的最大载荷为2.33 kN,达到母材AA1060的75%。

Microstructure and mechanical properties of pulsed laser welded Al/steel dissimilar joint

Pulsed laser welding was used in joining pure aluminum to stainless steel in a lap joint configuration. It is found that the mechanical properties of the laser joints were closely correlated with the bead geometry, i.e., penetration depth. In order to study the correlation, two typical laser welds with different penetration depths were analyzed. In high penetration depth (354 μm) joint, Al-rich Fe?Al IMCs with microcracks were formed at the Al/fusion zone (FZ) interface. The joint strength was found to be (27.2±1.7) N/mm and three failure modes were observed near the Al/FZ interface. In low penetration depth (108 μm) joint, Fe-rich Fe?Al IMCs without any defect were formed at the Al/FZ interface. The joint strength was found to be (46.2±1.9) N/mm and one failure mode was observed across the FZ.

Structure and mechanical properties of aluminum alloy/Ag interlayer/steel non-centered electron beam welded joints

Electron beam welding was carried out between aluminum alloy and steel with Ag interlayer. Seam morphology, structure and mechanical properties of the joints were investigated with different action positions of the electron beam spot. The results show that with the increment of the beam offset to the silver side from the interface between silver and steel, the seam morphology was improved, and the porosity in the Ag interlayer vanished. A transition layer mainly composed of Ag2Al and Al eutectic was formed at the interface between silver and aluminum, and became thin and spiccato as the beam offset increased. When the beam offset was too large, two IMC layers composed of FeAl and FeAl3 respectively were formed at the interface between steel and Ag interlayer. The optimal beam offset was 0.2 mm, and the maximum tensile strength of the joint was 193 MPa, 88.9% that of the aluminum alloy, and the fracture occurred at the interface between steel and Ag interlayer.

Contact reactive brazing of Al alloy/Cu/stainless steel joints and dissolution behaviors of interlayer

Contact reactive brazing of 6063 Al alloy and 1Cr18Ni9Ti stainless steel was researched by using Cu as interlayer. Effect of brazing time on microstructure of the joints, as well as the dissolution behaviors of Cu interlayer was analyzed. The results show that the product of reaction zone near 1Cr18Ni9Ti is composed of Fe2Al5, FeAl3 intermetallic compound （IMC）, and Cu-Al IMC; the near by area is composed of Al-Cu eutectic structure with Al （Cu） solid solution. With increasing the brazing time, the thickness of IMC layer at the interface increases, while the width of Al-Cu eutectic structure with Al（Cu） solution decreases. Calculation shows the dissolution rate of Cu interlayer is very fast. The complete dissolution time is about 0.47 s for Cu interlayer with 10 μm in thickness used in this study.

Residual stress and welding distortion of Al/steel butt joint by arc-assisted laser welding-brazing

The thermo-elastic.plastic finite element method(FEM)is used to simulate the thermo-mechanical behavior of Al/steel tungsten inert gas(TIG)arc-assisted laser welding-brazing(A-LWB)butt joint.The influence of material nonlinearity,geometrical nonlinearity and work hardening on the welding process is studied,and the differences in the welding temperature field,residual stress and welding distortion by A-LWB and by single laser welding-brazing(SLWB)are analyzed.The results show that the thermal cycle,residual stress distribution and welding distortion by the numerical simulation are in good agreement with the measured data by experiments,which verifies the effectiveness of FEM.Compared with the SLWB,A-LWB can make the high-temperature distribution zone of weld in width direction wider,decrease the transverse tensile stress in the weld and reduce the distribution range of longitudinal tensile stress.And the welding deformation also decreases to some extent.

Effect of process parameters on microstructure and properties of laser welded joints of aluminum/steel with Ni/Cu interlayer

The effects of laser parameters and interlayer material on the microstructure and properties of the welded joint between 6061 aluminum alloy and stainless steel were studied.The results show that the density and microstructure of the welded joint can be optimized by changing the laser power with 0.05 mm Cu foil and 0.1 mm Ni foil as interlayer.A large number of new Cu-Al binary phases were found near the aluminum alloy,which effectively inhibited the formation of the binary brittle phase of Fe-Al.The maximum shear force of 1350.96 N was obtained with laser power of 2200 W.The shear force of the welded joint increased to 1754.73 N when the thickness of the Cu foil thickness changed to 0.02 mm.

Effect of wire mesh interlayer in explosive cladding of dissimilar grade aluminum plates

Explosive cladding of Al 5052–Al 1100 plate, interfaced with a stainless steel wire mesh interlayer, is attempted. Loading ratio and standoff distance were varied. An increase in loading ratio (R) and standoff distance (S) enhances the plate velocity (Vp), dynamic bend angle (β) and pressure developed (P). The interface morphology of the explosive clads confirms strong metallurgical bond between the wire mesh and aluminum plates. Further, a smooth transition from straight to undulating interlayered topography is witnessed. The introduction of a wire mesh, as interlayer, leads to an improvement in mechanical strength with a slender reduction in overall corrosion resistance of the “explosive clads”.

Formation mechanism and control of aluminum layer thickness fluctuation in embedded aluminum-steel composite sheet produced by cold roll bonding process

The influences of rolling reduction and aluminum sheet initial thickness(AIT)on the thickness fluctuation of aluminum layer(TFA)of embedded aluminum?steel composite sheet produced by cold roll bonding were investigated,the formation mechanism of TFA was analyzed and method to improve the thickness uniformity of the aluminum layer was proposed.The results showed that when the reduction increased,TFA increased gradually.When the reduction was lower than40%,AIT had negligible effect on the TFA,while TFA increased with the decrease of AIT when the reduction was higher than40%.The non-uniformities of the steel surface deformation and the interfacial bonding extent caused by the work-hardened steel surface layer,were the main reasons for the formation of TFA.Adopting an appropriate surface treatment can help to decrease the hardening extent of the steel surface for improving the deformation uniformity during cold roll bonding process,which effectively improved the aluminum thickness uniformity of the embedded aluminum/steel composite sheets.

Microstructure and mechanical properties of Al-Fe meshing bonding interfaces manufactured by explosive welding

In order to improve the mechanical properties of Al.Fe transition joints manufactured by explosive welding,meshing bonding interfaces were obtained by prefabricating dovetail grooves in base plates.The microstructure and mechanical properties of the meshing interfaces were systematically investigated.The microstructure observation showed that metallurgical bonding without pores was created in the form of direct bonding and melting zone bonding at the interface.Fractography on tensile specimens showed cleavage fracture on the steel side and ductile fracture on the aluminum side near the interfaces.The tensile shear test results indicated that the shear strength of the meshing interface 0°and 90°was increased by 11%and 14%,respectively,when being compared to that of the ordinary Al.Fe transition joints.The values of microhardness decreased as the distance from the interface increased.After three-point bending,cracks were observed at the bonding interface for some specimens due to the existence of brittle Fe.Al compounds.

Effect of Tool Shoulder and Pin Probe Profiles on Friction Stirred Aluminum Welds-a Comparative Study

In marine application,marine grade steel is generally used for haul and superstructures.However,aluminum has also become a good choice due to its lightweight qualities,while rusting of aluminum is minimal compared to steel.In this paper a study on friction stir welding of aluminum alloys was presented.The present investigation deals with the effects of different friction stir welding tool geometries on mechanical strength and the microstructure properties of aluminum alloy welds.Three distinct tool geometries with different types of shoulder and tool probe profiles were used in the investigation according to the design matrix.The effects of each tool shoulder and probe geometry on the weld was evaluated.It was also observed that the friction stir weld tool geometry has a significant effect on the weldment reinforcement,microhardness,and weld strength.

Effect of Mg and Si on intermetallic formation and fracture behavior of pure aluminum-galvanized carbon-steel joints made by weld-brazing

Commercial pure aluminum and galvanized carbon steel were lap-welded using the weld-brazing(WB)technique.Three types of aluminum filler materials(4043,4047,and 5356) were used for WB.The joint strength and intermetallic compounds at the interface of three series of samples were analyzed and compared.Depending on the Si content,a variety of ternary Al-Fe-Si intermetallic compounds(IMCs) such as Fe_(4)(Al,Si)_(13),Fe_(2) Al_(8) Si(τ_(5)),and Fe_(2) Al_(9) Si_(2)(τ_(6)) were formed at the interface.Mg element in 5356 filler material cannot contribute to the formation of Al-Fe intermetallic phases due to the positive mixing enthalpy of Mg-Fe.The presence of Mg enhances the hot cracking phenomenon near the Al-Fe intermetallic compound at the interface.Zn coating does not participate in intermetallic formation due to its evaporation during WB.It was concluded that the softening of the base metal in the heat-affected zone rather than the IMCs determines the joint efficiency.

New development of powder metallurgy in automotive industry

The driving force for using powder metallurgy(PM)mostly relies on its near net-shape ability and cost-performance ratio.The automotive application is a main market of PM industry,requiring parts with competitive mechanical or functional performance in a mass production scale.As the automobile technology transforms from traditional internal combustion engine vehicles to new energy vehicles,PM technology is undergoing significant changes in manufacturing and materials development.This review outlines the challenges and opportunities generated by the changes in the automotive technology for PM.Low-cost,high-performance and light-weight are critical aspects for future PM materials development.Therefore,the studies on PM lean-alloyed steel,aluminum alloys,and titanium alloy materials were reviewed.In addition,PM soft magnetic composite applied to new energy vehicles was discussed.Then new opportunities for advanced processing,such as metal injection molding(MIM)and additive manufacturing(AM),in automotive industry were stated.In general,the change in automotive industry raises sufficient development space for PM.While,emerging technologies require more preeminent PM materials.Iron-based parts are still the main PM products due to their mechanical performance and low cost.MIM will occupy the growing market of highly flexible and complex parts.AM opens a door for fast prototyping,great flexibility and customizing at low cost,driving weight and assembling reduction.

Microstructure of aluminum/copper clad composite fabricated by casting-cold extrusion forming

An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significantly refined.In the center area of the copper,the grains are bigger than those at the boundary.On the surface of the deformable body,the grain size is the smallest,but with irregular grain morphology.After the product is entirely extruded,all the copper and aluminum grains are refined with small and uniform morphology.In the center area,the average diameter of aluminum grains is smaller than 5 μm,and the copper grain on the surface is about 10 μm.At the interface,the grain size is very small,with a good combination of copper and aluminum.The thickness of interface is in the range of 10-15 μm.Energy spectrum analysis shows that CuAl3 phase presents at the interface.

Prediction and optimization of friction welding parameters for joining aluminium alloy and stainless steel

Friction welding （FW） is a process of solid state joining which is used extensively in recent years due to its advantages such as low heat input,production efficiency,ease of manufacture and environment friendliness.Friction welding can be used to join different types of ferrous metals and non-ferrous metals that cannot be welded by traditional fusion welding processes.The process parameters such as friction pressure,forging force,friction time and forging time play the major roles in determining the strength of the joints.In this investigation an attempt was made to develop an empirical relationship to predict the tensile strength of friction welded AA 6082 aluminium alloy and AISI 304 austenitic stainless steels joints,incorporating above said parameters.Response surface methodology （RSM） was applied to optimizing the friction welding process parameters to attain the maximum tensile strength of the joint.

Effect of Si content on interfacial reaction and properties between solid steel and liquid aluminum

The effect of Si content on the microstructures and growth kinetics of intermetallic compounds(IMCs)formed during the initial interfacial reaction(<10 s)between solid steel and liquid aluminum was investigated by a thermophysical simulation method.The influence of Si addition on interfacial mechanical properties was revealed by a high-frequency induction brazing.The results showed that IMCs layers mainly consisted ofη-Fe_(2)Al_(5)andθ-Fe_(4)Al_(13).The addition of Si reduced the thickness of the IMCs layer.The growth of theηphase was governed by the diffusion process when adding 2 wt.%Si to the aluminum melt.When 5 wt.%or 8 wt.%Si was added to aluminum,the growth was governed by both the diffusion process and interfacial reaction,and ternary phaseτ1/τ9-(Al,Si)_(5)Fe_(3)was formed in theηphase.The apparent activation energies of theηphase decreased gradually with increasing Si content.The joint with pure aluminum metal had the highest tensile strength and impact energy.

Microstructure evolution and corrosion behavior of Fe-Al-based intermetallic aluminide coatings under acidic condition

Two Fe-Al-based intermetallic aluminide coatings were fabricated on 430-SS(Fe-Cr)and 304-SS(Fe-Cr-Ni)substrates by pressure-assisted solid diffusion bonding with coating on pure Fe as control.The microstructure and intermetallic phases of the coatings were characterized by SEM,EDS and EBSD.A network of Cr2Al13 with matrix of Fe4Al13 was formed by inter-diffusing of Al with the substrates.The corrosion behavior of intermetallic coatings was investigated in 0.5 mol/L HCl solution by mass-loss,OCP,Tafel plot and EIS.It was found that corrosion resistance was greatly enhanced by dozens of times after the addition of Cr and Ni compared with that on pure Fe.The presence of cracks in the coating on 430-SS provided a pathway for corrosion media to penetrate to the substrate and accelerated the corrosion rate.Moreover,the corrosion product was analyzed by XRD,demonstrating that the addition of Cr and Ni facilitated the formation of more corrosion resistant phases,and therefore improved corrosion resistance.

Improving pulsed laser weldability of duplex stainless steel to 5456 aluminum alloy via friction stir process reinforcing of aluminum by BNi-2 brazing alloy

Effects of laser pulse distance and reinforcing of 5456 aluminum alloy were investigated on laser weldability of Al alloy to duplex stainless steel (DSS) plates. The aluminum alloy plate was reinforced by nickel-base BNi-2 brazing powder via friction stir processing. The DSS plates were laser welded to the Al5456/BNi-2 composite and also to the Al5456 alloy plates. The welding zones were studied by scanning electron microscopy, X-ray diffractometry, micro-hardness and shear tests. The weld interface layer became thinner from 23 to 5 μm, as the laser pulse distance was increased from 0.2 to 0.5 mm. Reinforcing of the Al alloy modified the phases at interface layer from Al-Fe intermetallic compounds (IMCs) in the DSS/Al alloy weld, to Al-Ni-Fe IMCs in the DSS/Al composite one, since more nickel was injected in the weld pool by BNi-2 reinforcements. This led to a remarkable reduction in crack tendency of the welds and decreased the hardness of the interface layer from ~950 HV to ~600 HV. Shear strengths of the DSS/Al composite welds were significantly increased by ~150%, from 46 to 114 MPa, in comparison to the DSS/Al alloy ones.

Physical and chemical performances of high Al steels

The effects of acid-soluble Al content on the physical and chemical performances of high Al steels were investigated. The results show that the distribution of acid-soluble Al in steel substrate is uniform. With increasing Al content, the strength and toughness of steels decrease a little but the hardness increases. The average yield strength and tensile strength are 425MPa and 570MPa, respectively, and the Rockwell hardness is 89.7. For non-Al steels the average oxidation rate is up to 0.421mg/(cm2·h) at 1373K. For high Al steels, when the mass fraction of Al is less than 5%, there is a thinner gray oxidized layer on surface and the oxidation rate is high; when the mass fraction of Al is more than 8.0%, the thin, close and yellow glossing film still exists, and the average oxidation rate is only 0.016mg/(cm2·h).

Effects of welding parameters and tool geometry on properties of 3003-H18 aluminum alloy to mild steel friction stir weld

Defect-free butt joints of 3003 Al alloy to mild steel plates with 3 mm thickness were performed using friction stir welding （FSW）. A heat input model reported for similar FSW was simplified and used to investigate the effects of welding speed, rotation speed and tool shoulder diameter on the microstructure and properties of dissimilar welds. The comparison between microstructure, intermetallics and strength of welds shows the good conformity between the results and the calculated heat input factor （HIF） achieved from the model. The joint strength is controlled by Al/Fe interface at HIF of 0.2-0.4, by TMAZ at HIF of 0.4-0.8 and by intermetallics and/or defects at HIF0.8.

Development and characterization of hot dip aluminide coated stainless steel 316L

Stainless steel(SS)grade 316L is used for orthopedic implants due to its biocompatibility;yet the effort should be done to minimize the carcinogenic and inflammatory effects related to SS 316L implants.In this research,aluminide coating of Al–Si alloy on SS 316L is characterized by using optical microscopy,energy dispersive spectroscopy(EDS),nano-indentation and corrosion testing technique.Hot dip aluminizing process is used to coat the SS 316L specimens at 765°C for 2 min immersion time.Half of the specimens are also diffusion treated in a Muffle furnace at 550°C for 4 h to produce diffused specimens of SS 316L.Microstructural examination shows the formation of flat coating/substrate interface due to Si addition.EDS analysis confirms the formation of complex intermetallic at the coating/substrate interface which finally results in increasing the hardness and corrosion resistance properties of coating.