Copper Backing Plate Research Articles

Experimental investigation into friction stir welding of AA6061-T6 and magnesium AZ31B alloy using copper backing plate

Aluminium-magnesium alloys are lightweight and possess superior properties, making them ideal for applications in aerospace, railway, automotive, and marine structures. However, these alloys are challenging to fabricate using traditional fusion welding due to various metallurgical issues. This study investigates the feasibility of joining 3 mm thick dissimilar alloys of aluminium AA6061-T6 and magnesium AZ31B using the friction stir welding (FSW) process with copper as a backing plate. The effects of FSW process parameters, including tool rotational speed (380, 545, 765 rpm), weld speed (20, 31.5, 50 mm min−1), and tilt angle (1°, 2°, 3°), on tensile properties were examined using Taguchi-based grey relational analysis. Temperatures were recorded during the FSW process under different conditions on both sides of the joint. The highest tensile strength of 130.72 MPa, with a joint efficiency of 67.85%, was achieved at a tool rotational speed of 765 rpm, a welding speed of 50 mm min−1, and a tilt angle of 2°. Analysis of variance (ANOVA) for the grey relational grade indicated that the tilt angle had the highest percentage contribution of 43.60%. This study demonstrates the significant influence of FSW parameters on the mechanical properties of aluminium-magnesium joints and highlights the optimal conditions for achieving high joint strength and efficiency.

Improving the stability of the friction stir channelling technology via a cooled copper backing plate

The development of the friction stir channelling (FSC) technology has a potential to revolutionize the manufacturing industry, providing an innovative way to produce continuous sub-surface channels in monolithic components in a single step. However, the process generates heat that can lead to defects and loss of stationarity, affecting the quality of the channels produced and the process’ efficiency and control. To address these challenges, a ground-breaking study was conducted using a cooled copper backing plate to adjust the process temperatures and investigate the influence of the temperature on FSC stability. The results of the study showed that the cooled copper backing plate has a significantly higher rate of heat conduction, effectively preventing the processed component from overheating and ensuring that the process maintains its stationarity. When using the steel backing plate, only one combination of process parameters (a rotation speed of 450 rev/min and a traverse speed of 71 mm/min) yielded satisfactory results. Moreover, the use of the cooled copper backing plate allowed for a wider range of process parameters to be employed, resulting in sub-surface channels with higher quality and fewer defects. The 710/71 parameters combination resulted in a lower heat input, while the 900/45 parameters set produced channels with a more rectangular geometry. A rotation speed of 900 rev/min and a traverse speed of 45 mm/min have been shown to be the best choice. This innovative approach to FSC technology represents a major step forward in solid-state manufacturing, envisaging new possibilities for producing longer sub-surface channels with superior quality and greater efficiency.Highlights• Conducting the FSC process at low temperature has improved its stability.• The use of a cooled copper backing plate enabled a broader range of FSC process parameters.• Longer and stabler leak-free sub-surface channels have been produced in aluminium alloys.Graphical

Ductile fracture of 2024 aluminum under unequal biaxial in-plane tension and out-of-plane compression

The ductile fracture of 2024 aluminum loaded under unequal in-plane biaxial tension and out-of-plane compression is investigated. This stress state is induced in materials during ballistic impacts. A novel experimental design is presented which utilizes an elliptical shaped punch to induce unequal amounts of tension along the in-plane axes of a thin specimen plate. An annealed copper backing plate placed behind the specimen induces out-of-plane compression. Fracture is observed directly with Digital Image Correlation during continuous loading of unbacked specimens. Interrupted testing and acoustic emissions are used to determine the instant of fracture in tests where a backing plate is used. Numerical simulations are performed using an assumed plasticity model, and the model is validated by matching the simulated force-displacement response and strain with the experiments. The equivalent plastic fracture strain is determined for various stress states that correspond to averaged triaxiality values ranging from 0.14 to 0.61 and averaged Lode parameter values ranging from −0.72 to −0.29.

Free Intermetallic Cladding Interface between Aluminum and Steel through Friction Stir Processing

In this paper, the cladding of pure aluminum and a low-carbon steel alloy was performed through friction stir processing with minimal intermetallic compound formation. A 3 mm thick aluminum plate was clamped on top of a steel plate. A thick, pure copper plate was used as a backing plate. The tool pin length was adjusted to be the same as the upper plate’s thickness (3 mm) and longer than 3.2 mm. The effect of the tool pin length and the rotation speed (500–1500 rpm) on the cladding’s quality, microstructure, and the mechanical properties of the steel/aluminum interface were investigated using optical and scanning electron microscopy, a hardness test, and a peel test. The results showed that the bonding of pure aluminum and a low-carbon steel alloy can be successfully performed at a more than 500 rpm rotation speed. At a tool pin length of 3 mm and a rotation speed of 1000 rpm, sound and free-intermetallic compound–cladding interfaces were formed, while some Fel2Al5 intermetallics were formed when the rotation speed was increased to 1500 rpm. The pure copper backing plate has an essential role in eliminating or reducing the formation of intermetallic compounds in the cladding interface. When the tool pin length was increased to 3.2 mm, more steel fragments were found on the aluminum side. Moreover, with a higher rotation speed and longer tool pin length, more Fe2Al5 intermetallics were formed at the interface. Increasing the rotation speed and the pin tool length contributed to the enhancement of interface bonding. Meanwhile, the maximum tensile shear load was obtained at a rotation speed of 1500 rpm and a tool pin length of 3.2 mm. In addition, the hardness values of the interface were higher than the aluminum base metal for all the investigated samples. Decreasing the rotation speed and increasing the tool pin length can significantly increase hardness measurements. The average hardness increases from 42 HV of the pure aluminum to 143 HV at a rotation speed and a tool pin length of 1500 rpm and 3.2, respectively.

The influence of the backing plate materials on microstructure and mechanical properties of friction spot extrusion brazing of AA2024-T3 aluminum alloy and Brass sheets

In this study, the impact of the backing plate materials on microstructural and mechanical features during friction spot extrusion brazing of AA2024-T3 aluminum alloy and brass sheets by inserting Zn as an interlayer was investigated. Results indicated that the change of the backing plate material influentially affected the microstructure of the reaction layers at the interface of the AA2024/Zn/brass joint. Besides, it was found that the Zn interlayer could restrict the creation of deleterious intermetallic compounds at the interface. Moreover, the attained data revealed that the weld produced by the steel backing plate raised the fracture load of the joint in comparison to the other weld obtained by the copper backing plate by 35% even though the peak temperature was enhanced with a change in the backing plate material from copper to steel. The improvement in the tensile result of the steel backing plate-produced joint is owing to the good metallurgical bonding (complete filling of the pre-threaded hole) and presence of a larger amount of Al-Zn eutectic phase at the brazed zone.

Pre-strain assisted low heat-input friction stir processing to achieve ultrafine-grained copper

In this study, the effects of pre-rolling and friction stir processing (FSP) on the microstructure and mechanical behavior of pure copper were investigated. With increasing the tool rotational speed from 400 to 800 rpm, the average grain size increased for both 0% (annealed) and 60% (pre-rolled) samples. Also, pre-rolling of copper led to a reduction in the average grain size of the FSPed samples. It was found that homogeneously distributed fine grains structure in the 400–100 (0%) (400 rpm–100 mm/min – with 0% pre-rolling), 400–100 (60%), and 800–100 (60%) samples were observed due to the large heat transfer caused by the copper backing plate. The application of rolling and FSP caused an improvement in hardness, yield strength, and ultimate tensile strength values due to the grain refinement mechanism. Among the FSPed samples, the 600–100 (60%) sample showed a better strength-ductility balance than the other samples. In the initial and FSPed samples, many dimples were observed, revealing the ductile fracture. With increasing the rotational speed, the dimples morphology became more homogeneous. Also, the pre-rolled samples had dimples smaller than the annealed samples.

Effect of backing plate on mechanical and microstructural properties of tungsten inert gas welded AA 6063 butt joints

In the present scenario, ship building industries are frequently associated with welding process to explore the benefits of improved strength over the parent material. Development of new techniques to enhance the processes is of a part of the usual practice in industries. In the present work, as a supportive measure, backing plate was introduced to develop the weldments with enhanced properties. The central composite design array specimens, a widely used aluminum alloy in marine application AA 6063 were prepared by TIG welding process with the help of backing plates of different materials. Effect of backing plate material on the properties such as ultimate tensile strength and microhardness of the weld joints were investigated. A detailed study of microstructure and macrostructure on the weldment was also done. Results exhibit a considerable improvement for the recommendation of using copper backing plates in the welding processes.

Tailoring grain refinement through thickness in magnesium alloy via stationary shoulder friction stir processing and copper backing plate

To develop ultrafine grains (UFG) in 6.35 mm thick magnesium alloy, stationary shoulder friction stir processing (SSFSP) with steel and copper backing plates was conducted. Steel backing plate produced uniform fine grains (FG) size of 4.98, 4.75, 4.12 μm in top, middle, bottom of the stir zone (SZ), respectively. In contrast, copper backing plate tailored microstructure from FG (4.1 μm) in the top to UFG (0.96 μm) in the bottom of SZ. SSFSP produced uniform and gradient microstructures, altering temperature gradient by placing steel and copper backing plates, respectively. It is worth to note that UFG microstructure achieved without usage of external cooling, owning to the copper backing plate. Most of the grains found under ~2 μm size in UFG microstructure. FG and UFG microstructures contributed to the enhancement in the ductility and strength, respectively. UFG resulted in significant improvement in hardness and tensile strength by ~80% and 24% of the base material, respectively. The intensity of strong basal texture throughout the thickness found independent of the backing plate type. Microstructure evolutions across the SZ thickness for both processing conditions are discussed using electron back scattered diffraction (EBSD).

Thermal Cycles and Deformation Characters During High-Speed Micro Friction Stir Welding Process of AA7075-T6 Sheets

Thermal cycles and deformations during high-speed micro friction stir welding (μFSW) under different welding conditions were studied by experimental methods. The results show that the peak temperature and elevated-temperature exposure time (t150) increased with the increasing of rotational speed and decreased with the increasing of welding speed. Increasing rotational speed or welding speed led to an increase in both heating and cooling rates. The joint fabricated by the pinless tool experienced a lower peak temperature, a shorter elevated-temperature exposure time, and a larger temperature gradient than that by the pin tool. The welded sheet presented an anti-saddle deformation character, with convex bending in a longitudinal direction and concave angular bending in a transverse direction. In comparison to the pin tool, the longitudinal maximum bending deformation, Zmax, of the joint fabricated by the pinless tool was reduced by 12.35%, and the transverse angular deformation, α, was reduced by 6.67%. In comparison to the steel backing plate, the Zmax of the joint produced using a copper backing plate was reduced by 40.66%, but the α was increased by 53.27%.

Optimal Design of Co/In/Cu Sputtering Target Assembly Using Finite Element Method and Taguchi Method

Target assembly is a key consumable material for producing thin film used in the electronic packaging and devices. The residual stresses induced during the process of soldering are detrimental to the performance of target assembly. In this work, the intensity and distribution of the soldering residual stress of Co/In/Cu target assembly subjected to a 20 W/(m2 K) cooling condition corresponding to the actual air cooling process were studied, based on finite element simulation and Taguchi method, to optimize the sputtering target assembly. Effects of different control factors, including solder material, thickness of solder layer, target and backing plate, on the soldering residual stress of target assembly are investigated. The maximum residual stress is calculated as 9.28 MPa in the target located at 0.16 mm from target–solder layer interface and at a distance of 0.78 mm from symmetry axis. The optimal design in target assembly has the combination of indium solder material, cobalt target at 12 mm thick, solder layer at 0.8 mm thick, copper backing plate at 15 mm thick. Moreover, solder material is the most important factor among control factors in the target assembly.

Investigation of the thermal performance of natTe target for 124I production in the RARS cyclotron

Abstract Regarding the low thermal conductivity of natTe element, the provision of an effective cooling system is one of the critical issues in cyclotron targetry to prevent melting of target matter during the irradiation to 124I production via natTe(p,xn)124I reaction. Heat transfer on Te target and efficiency of cooling fluid in the solid target system have been simulated based on a Finite Element Analysis (FEA) code for the thermal behavior of the target during the irradiation and under different beam currents, coolant flow rates, substrate matters and target geometry. The results on the routinely used solid target in Radiation Application Research School (RARS) cyclotron showed that in a 3 m/s coolant flow rate, by using a fined-cooling system and a nickel substrate coated on copper backing plate, the irradiation beam current can be raised up to 180 μA without any risk of melting. The cooling flow rates greater than 3 m/s do not noticeably improve the heat dispersion of target layer. As expected, a linear increase was observed for the temperature and temperature gradient of plates in the beam currents of 100–300 μA.

Active soldering of ZnS–SiO2 sputtering targets to copper backing plates using an Sn3.5Ag4Ti(Ce, Ga) filler metal

An Sn3.5Ag4Ti(Ce, Ga) active solder is used for joining ZnS–SiO2 ceramic sputtering targets with copper backing plates at 250 °C in air. Direct soldering using the Sn3.5Ag4Ti(Ce, Ga) metal filler has been found to be a reliable and simple technique for ZnS–SiO2 ceramic bonding with ZnS–SiO2 and copper. The shear strengths for ZnS–SiO2/ZnS–SiO2 and ZnS–SiO2/Cu joints are 6.5 and 5.2 MPa, respectively. The bonding mechanism is described, with emphasis placed on the action of a rare earth element (Ce) and the active metal reaction. The interfacial reaction between Sn3.5Ag4Ti(Ce, Ga) filler metal and copper at temperatures ranging from 120 to 200 °C is conducted and discussed.

Active Soldering of ZnS–SiO2 Sputtering Targets to Copper Backing Plates Using an Sn56Bi4Ti(Ce, Ga) Filler

ZnS–SiO2 targets have been directly soldered to copper backing plates at 180°C in air using an Sn56Bi4Ti(Ce, Ga) filler. The affinity of cerium to oxygen protects titanium from oxidation, allowing titanium to react with ZnS–SiO2 sputtering target. The shear strengths are 1.7, 8.7, and 1.3 MPa for ZnS–SiO2/ZnS–SiO2, copper/copper and ZnS–SiO2/copper joints, respectively. EPMA elemental mapping shows that aging test at 120° for 100 hours enhanced the segregation of titanium at the ZnS–SiO2/solder interfaces. The shear strength of ZnS–SiO2/copper joint after aging test is 1.3 MPa that shows no trace of degradation compared to the initial quality of the samples.

Friction stir welding of copper and copper alloys

Copper, through having good thermal conductivity and a relatively high melting point, generally requires preheating treatment to maintain satisfactory penetration during arc welding, ranking as a hard-to-weld material. Like aluminium and magnesium, however, copper is basically a soft metal and can therefore be relatively easily joined by friction stir welding. Available FSW research has focused on fabrication of copper (oxygen-free copper) containment canisters for nuclear waste,1–6 fabrication of copper backing plates for sputtering devices by FSW seal welding,7, 8 and some other applications,9 whereas FSW research on copper alloys has thus far been little documented.10, 11 Related research topics include studies of Al alloy to Cu alloy dissimilar joints12, 13 as well as – although not quite the same as friction stir welding – friction stir processing of Ni–Al bronze for casting structure modification14–16 and friction stir processing of a Cu–Mn alloy for surface modification purposes.17

Finite element modelling of tungsten inert gas welding of aluminium alloy 2024

A finite element model to predict the evolution of stress and distortion for a bead on plate tungsten inert gas (TIG) weld in aluminium alloy 2024 plate is described. The thermal model was calibrated against thermocouple measurements, and the mechanical model was validated against direct measurements of residual strain made using synchrotron X-ray diffraction. Particular attention has been paid to the clamping arrangement, the transfer of heat between the plate and the copper backing plate, and the selection of appropriate thermal history dependent mechanical properties. The validated model has been used to determine the optimal arrangement for 'low stress no distortion' welding using laser heating applied to both sides of the joint line ahead of the TIG torch. In this manner it is predicted that the peak longitudinal tensile stresses in the weld region can be reduced to 15% of their normal values.

Ion assisted deposition of Zn–Mg coatings by unbalanced magnetron sputtering

Several patents have recently been assigned to Japanese coated sheet steel producers for the invention of novel vapour deposited Zn–Mg alloy coatings. Claims have been made that the coating compositions and microstructures attainable provide significant improvements in the corrosion resistance compared with hot-dip galvanized products. In response to this industrial interest, a range of Zn–Mg coatings were prepared by unbalanced magnetron sputtering, with the aim of investigating the effects of ion assistance on coating composition. Circular planar targets consisting of sequential sectors of Zn and Mg, bonded to a directly cooled copper backing plate, were used for the preparation of alloy coatings. Ion assistance resulted in the preferential resputtering of Mg from the alloy coatings. Monte Carlo simulations using the T-DYN code revealed this was mainly due to the sputter yield amplification effect. Ion assistance also resulted in retention of exceptionally high proportions of Ar in the Zn–Mg coatings, particularly for the Mg-rich compositions. Coatings with high Ar content were sensitive to failure by heavy oxidation after aging at ambient conditions.

Stoichiometry of unbalanced magnetron sputtered Al–Mg alloy coatings

Abstract Numerous Al–Mg coatings were prepared by unbalanced magnetron sputtering with a range of substrate bias voltages. The coatings were deposited from circular planar targets, composed of sequential sectors of Al and Mg, bonded to a directly cooled copper backing plate. The chemical composition of the coatings was found to be significantly affected by preferential resputtering of Mg due to ion bombardment. X-ray diffraction indicated that all coatings were extremely fibre textured. Some dramatic changes in d -spacing of the coating were observed for only small increments in the bias voltage. This indicates a transition in crystal structure induced by preferential resputtering. Extremely high amounts of argon were also detected in the coatings which contained a Mg-rich cph structured phase. Very little argon was detected in any of the Al-rich fcc coatings, even with high substrate bias voltages (−200 V). The burial of argon in the cph structured Al–Mg coatings is not purely an ion implantation phenomenon, but is controlled by microstructural entrapment or alloying effects. It is concluded that ion-assisted deposition of Al–Mg alloy coatings should be treated with some caution, because of these difficulties with the control of stoichiometry.

母板，裏当て銅板間電圧の成因と裏ビード幅との関係 Ｉ フラックス銅裏当て方式（ＦＣＢ）片面溶接における裏ビード幅自動制御

A possibility of a back bead width control system have been proposed to stabilize the process of one side FCB SAW in which a stationary copper backing plate covered with a flux layer of several milimeter thickness is used as backing.When a stable welding process is maintained under an adequate welding condition, a signal voltage between the backing copper plate and the plate being welded have beeen detected. The polarity and phase of the detected voltage having a few volt level is well corresponding to those of the arc voltage in case of AC current welding.In a stable FCB SAW process, the back side bead is mostly formed by a key-hole action of the arc. It is assumed for the reason that the arc penetrates through' the welding groove and the flux layer, then it contacts the copper plate and is reflected to the welding plate. The correlation between the detected voltage level and the back side bead width is recognized.The similar phenomenon is observed in a key-hole welding by using a transfer type plasma arc welding.In order to maintain the back bead width constant the detecting voltage is compared with a reference voltage, and then the welding current is controlled by the difference of the above voltages.

Application of the sessile drop method to the determination of the surface energy and density of liquids wetting the backing material

1. A procedure, based on the sessile drop method, is proposed for determining the free surface energy and density of melts wetting the material of solids in contact with the latter. 2. On the examples of ethyl alcohol and vacuum oil, which wet copper, the possibility is shown of forced generation of drops with the maximum diameter on copper backing plates having the shape of a solid of revolution with an acute angle between the horizontal and the side surface. A linear relationship is shown to exist between the maximum angle formed by the horizontal and the tangent at any point on the wetting perimeter, and the edge point angle of the backing plate. 3. The method proposed was applied to the high-temperature determination of the free surface energy of copper and calcium fluoride on molybdenum backing plates. 4. The sessile drop method in conjunction with the proposed procedure for determining the free surface energy and density of liquids wetting the backing material is universal.