Bimetallic Sheets Research Articles

Microstructure and mechanical properties of butt-welded Ti/steel bimetallic sheet using various multi-principal filler wires

Ti/steel bimetallic sheets have attracted significant attention in various engineering fields. However, achieving high-quality welded joints of Ti/steel bimetallic sheet presents difficulties because of poor metallurgical compatibility and different thermal expansion coefficients between titanium and steel. In this study, four types of multi-principal filler wires with varying contents of Cu, Ni, and Ti elements were designed and manufactured to finish the welding of TA2/Q235 bimetallic sheets. The study investigated the effects of various filler wires on the hardness, tensile strength, corrosion resistance, and microstructure of the welded joints. An interesting finding is that the highest tensile strength of 327±6 MPa was achieved in the welded joint using FeCoNi2Ti0.5 filler wire, with a joint coefficient of ∼79.1 %. The highest hardness in the weld zones was achieved by using FeCoNiTi0.5 filler wire, while the lowest hardness was achieved using FeCoNiCu0.5 filler wire. Dendrite (DR), interdendritic (ID), and eutectic structures were consistently observed in these weld zones. The phases of the DR and ID were identified as Fe2Ti and FCC structures based on EBSD data. A high content of Ni in filler wires could reduce the size and content of the Fe2Ti phase in the weld zones of Ti/steel bimetallic sheets.

Achieving excellent bond strength and tensile strength synergy of ultrafine-grained Al/Cu bimetallic sheets developed by an innovative hybrid manufacturing process

In the present work, two new parameters that influence the bond strength and tensile strength of Al/Cu bimetallic sheets are explored using an innovative hybrid manufacturing process. The innovative hybrid manufacturing process includes engineering of four different microstructures, 1. Ultrafine grained (UFG); 2. Bimodal grained (BM); 3. Fine grained (FG) and 4. Coarse grained (CG) in parent Cu and Al via integration of cryogenic based thermo-mechanical treatment followed by an unique tailored criss-cross surface pattern generation and high deformation roll bonding to develop high performance Al/Cu engineered sheets with four microstructural combinations: UFG‐Al + UFG-Cu, UFG‐Al + BM-Cu, UFG‐Al + FG-Cu and CG‐Al + CG-Cu. The criss-cross pattern aids in initiation of crack at the junctions and fissure formations at cross paths during the roll bonding process. This kind of pattern develops mechanical bond in the form of nugget bunches, which result in enhancement of bond strength in all the microstructural combinations of Al/Cu bimetallic sheets. The ascending order of increase in bond strength-tensile strength synergy of all four engineered microstructural combinations is: CG‐Al + CG-Cu, UFG‐Al + FG-Cu, UFG‐Al + BM-Cu and UFG‐Al + UFG-Cu. The UFG‐Al + UFG-Cu combination has achieved an extraordinary bond strength of 18 N/mm, which is almost 1.6 times the bond strength of its conventional coarse grained counterpart CG‐Al + CG-Cu combination (10 N/mm). Similarly, the UFG‐Al + UFG-Cu combination showed excellent tensile strength of 323 MPa which is around 25 % higher than that of CG‐Al + CG-Cu combination (258 MPa). The engineered UFG microstructure in Al and Cu samples promote the dynamic recrystallization and partial diffusion kinetics at the interface region and established the mechanical and metallurgical bonding between Al/Cu bimetallic sheets during roll bonding process. The adopted surface pattern and the engineered microstructure have enhanced the bond strength and tensile strength of Al/Cu bimetallic sheets both at macro and micro levels. The underlying scientific knowhow for obtaining excellent bond strength-mechanical property synergy in the engineered Al/Cu bimetallic sheets are established.

Effect of Ti content on weld formation and mechanical properties of welded joints of TA2/Q235 bimetallic sheets

Due to the issue of brittle Ti-Fe intermetallic compounds, a challenge for the welding of Ti/steel bimetallic sheets is presented. In this study, four types of multi-principal powders of Fe25-xCo25Ni25Cu25Tix were designed based on eutectic high-entropy alloys (HEAs), which were used as filler materials for laser welding of TA2/Q235 bimetallic sheets. The impact of Ti content in the filler powders on weld formation and mechanical properties was investigated. It is found that with an increase in the Ti content, the hardness values of the weld zones generally increased, whereas the tensile strengths decreased. The maximum tensile strength of ∼298.4 MPa was achieved in the joint using Fe20Co25Ni25Cu25Ti5 filler powders, in which the weld metal met the definition of an HEA.

Experimental and Numerical Investigation of Forming Limit Diagrams during Single Point Incremental Forming for Al/Cu Bimetallic Sheets

This article investigated the formability of aluminum/copper bimetal sheets during single-point incremental forming. First, the two-layer sheets were produced by the explosive welding process; then, the rolling process was performed with 50% strain on two-layer samples. Considering the importance of examining the mechanical and metallurgical properties on the formability of the two-layer samples, the mechanical properties were first examined, including the uniaxial tensile and micro-hardness tests. Then, metallurgical tests were performed, including scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDX) to investigate the fracture surface and penetration depth and an X-ray diffraction (XRD) test to check the secondary phase particles in the penetration zone of Al and Cu in five different annealing temperature conditions. Considering that the forming limit diagram (FLD) is dependent on the strain path, to study the effect of the strain path, the two-layer samples were formed by three geometries: pyramid, cone, and straight groove. Simulations of FLD by Abaqus software 6.14-4 with four different methods were studied: FLDCRT, effective strain rate (ESR), second derivation of thinning (SDT), and maximum strain rate (MSR). The results showed that the FLDCRT criterion provided a more accurate estimate of the necking time. In the following, the values of the thickness distribution were carried out by experimental and numerical methods, and the results between the methods were in good agreement.

Laser Welding of Titanium/Steel Bimetallic Sheets with In Situ Formation of Fex(CoCrNiMn)Tiy High-Entropy Alloys in Weld Metal.

Due to the notable disparities in the physical and chemical characteristics between titanium and steel, the direct fusion of titanium/steel bimetallic sheets results in a considerable formation of fragile intermetallic compounds, making it difficult to achieve excellent metallurgical welded joints. In this study, a multi-principal powder of CoCrNiMn was designed and utilized as a filler material in the welding of the TA1/Q345 bimetallic sheet. It was expected that the in situ formation of Fex(CoCrNiMn)Tiy high-entropy alloys would be achieved using the filler powders, combined with the Ti and Fe elements from the melting of the TA1 and Q345 so as to restrain the generation of Fe-Ti IMCs and obtain the promising welded joints of the TA1/Q345 bimetallic sheet. An interesting finding is that high-entropy alloys were successfully obtained in the weld metal. The Fe-Ti intermetallic compounds at the welding interface were significantly reduced. The tensile strength was ~293 MPa, accounting for 60% of the strength of the base metal. Dimples were observed at the fracture of the welded joint.

Influence mechanism of copper interlayer on the interface bonding during wire and laser additive repair of TA1/Q235 bimetallic sheets

Influence mechanism of copper interlayer on the interface bonding during wire and laser additive repair of TA1/Q235 bimetallic sheets

Prediction of formability and effects of process parameters on the adhesively bonded composite metallic sheets

The study investigates the deep drawing process for bimetallic sheets formed by bonding dissimilar metals (AA1100 aluminium alloy and C36000 brass) with epoxy-based adhesive. Experimental exploration of process parameters, including blank diameter, stacking sequence, lubrication, and strain rate, was conducted to analyse their impact on load–displacement behaviour and thickness strain distribution. Additionally, the study assessed fracture susceptibility, material flow characteristics (tearing and wrinkling), and the requisite drawing force for the bonded specimens. Results indicate enhanced formability and mechanical properties in bonded sheets compared to individual metal sheets, demonstrating the potential advantages of this approach. The bonded sheets demonstrated improved formability and mechanical properties compared to individual metals. Notably, the maximum drawing force for the bonded sheet (170 mm diameter) significantly increased to 24.2 kN, surpassing individual sheets by 69.85% for AA1100 and 40.54% for C36000. The analysis identified a vulnerable region (12–15 mm from the centre) under maximum risk of failure and consistent deformation patterns in samples with varying diameters and lubrication, providing valuable insights into the behaviour of bonded bimetallic sheets in deep drawing.

Microstructural characterization and mechanical behavior of Mg-AZ31B/Al 6063 bimetallic sheets produced by combining continuous shear deformation with direct extrusion

To enhance the bonding effect and mechanical properties of hot-extruded Mg/Al bimetallic sheets, a novel bimetallic hot extrusion process called direct extrusion and continuous shear deformation (DECS) was proposed based on the shear deformation process. An extrusion die was designed and manufactured, and the influence of extrusion temperature on the microstructure and mechanical properties of the Mg/Al bimetallic sheet was investigated. Results showed that at an extrusion temperature of 330 ℃, defects and cracks appeared at the bonding interface, while favorable metallurgical bonding between Mg/Al bimetallic sheet was achieved at 370 ℃ and 410 ℃. The Mg layer exhibited a nearly complete dynamically recrystallized (DRXed) structure, with the average grain size increasing with higher extrusion temperature. A strong {0001} basal texture was observed in the Mg layer at 330 ℃ and 410 ℃. At 370 ℃, the combined action of shear strain between the bonding interfaces triggered the activation of multiple slip systems in the Mg layer, reducing the basal texture strength. The Al layer exhibited preferred orientations at various extrusion temperatures, particularly the multi-grain < 001 > and < 101 > orientations. The maximum shear strength of the formed sheet was determined to be 18.1 ± 3.7 MPa, with a maximum elongation of 38.4 %.

Experimental studies of formability in single point incremental forming of Cu-Al bimetallic sheets

In the sheet metal forming industry, single point incremental forming (SPIF) is gaining popularity for producing asymmetrical shapes in small quantities as well as developing rapid prototypes. In the present experimental study, the effect of process variables on the maximum forming wall angle of Cu-Al bimetallic composite sheet using the SPIF process has been investigated. The Cu-Al bimetallic composite sheet was considered for the investigation because of its qualities, including high strength and outstanding thermal and electrical conductivity. The range of step depth, spindle speed, forming speed, layer arrangement, and lubrication type were used as input process variables during the experiments. Formability is evaluated as an output parameter using the maximum forming wall angle. The findings revealed that the Cu-Al layer arrangement produced the greatest forming wall angle with the highest value, 81.5°, when employing 0.6 mm step depth, 1500 rpm spindle speed, 750 mm/min forming speed, and liquid lubrication. Liquid lubrication produced greater forming wall angle values than solid lubrication in all of the experiments. In both lubrication conditions, the Cu-Al layer arrangement exhibited a larger forming wall angle than the Al-Cu layer arrangement.

Features of structure formation when surfacing steel (iron) on titanium with plasma sprayed coatings in the technology of obtaining butt joint of bimetallic plates "titanium – steel"

The object of this study is structural formation during the surfacing of steel (iron) on titanium with plasma-sprayed coatings to obtain a butt connection of titanium-steel bimetallic plates. The task to be solved was to devise a technology for applying a barrier layer between titanium and steel to obtain a defect-free butt joint of the edges of bimetallic sheets of carbon steel, clad with a layer of titanium, under conditions of arc or plasma surfacing of carbon steel on titanium. The application of the barrier layer was carried out by plasma spraying of steel wire or iron powder. In this case, a coating with a thickness of 150...750 μm was applied on Grade2 titanium, on which 1–2 mm thick layers of materials similar to the sprayed ones were deposited by arc and plasma deposition. It was established that during spraying with subsequent surfacing of steel wire or iron powder, the main technological factors for eliminating cracks in the resulting compound are the thickness of the sprayed coating and the amount of linear surfacing energy. The thickness of the sprayed coating was selected (at least 400...600 microns) followed by plasma surfacing of ER70S-6 steel wire with a diameter of 1.0 mm or CNPC-Fe200 iron powder with unit energy up to ~200...250 J/mm. A defect-free transition layer from titanium to steel was obtained. It is a continuous layer with a thickness of 50–60 microns, consisting of intermetalides FeTi and FeTi2, as well as a β-phase titanium with an enhanced iron content, which retains certain ductility without cracks and other defects. With the help of the devised approach for connecting titanium-steel bimetallic edges, it is planned to manufacture seam bimetallic pipes for main pipelines to transport oil and gas raw materials extracted from wells.

Molten Salts Approach of Poly(vinyl alcohol)-Derived Bimetallic Nickel-Iron Sheets Supported on Porous Carbon Nanosheet as an Effective and Durable Electrocatalyst for Methanol Oxidation.

The preparation of metallic nanostructures supported on porous carbon materials that are facile, green, efficient, and low-cost is desirable to reduce the cost of electrocatalysts, as well as reduce environmental pollutants. In this study, a series of bimetallic nickel-iron sheets supported on porous carbon nanosheet (NiFe@PCNs) electrocatalysts were synthesized by molten salt synthesis without using any organic solvent or surfactant through controlled metal precursors. The as-prepared NiFe@PCNs were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction, and photoelectron spectroscopy (XRD and XPS). The TEM results indicated the growth of NiFe sheets on porous carbon nanosheets. The XRD analysis confirmed that the Ni1-xFex alloy had a face-centered polycrystalline (fcc) structure with particle sizes ranging from 15.5 to 30.6 nm. The electrochemical tests showed that the catalytic activity and stability were highly dependent on the iron content. The electrocatalytic activity of catalysts for methanol oxidation demonstrated a nonlinear relationship with the iron ratio. The catalyst doped with 10% iron showed a higher activity compared to the pure nickel catalyst. The maximum current density of Ni0.9Fe0.1@PCNs (Ni/Fe ratio 9:1) was 190 mA/cm2 at 1.0 M of methanol. In addition to the high electroactivity, the Ni0.9Fe0.1@PCNs showed great improvement in stability over 1000 s at 0.5 V with a retained activity of 97%. This method can be used to prepare various bimetallic sheets supported on porous carbon nanosheet electrocatalysts.

Mechanical Properties of Aluminium/Copper Bimetallic Sheets Subjected to Cyclic Bending

The aim of this study is to evaluate the influence of the roll bonding (RB) process on the mechanical properties of Al/Cu bimetallic strip specimens. A specially designed test instrument for the cyclic bending test of strip specimens produced by RB has been proposed. The test consists of repeated pulling of a strip of sheet metal through a system of cylindrical countersamples. Samples cut along and across the sheet rolling direction were tested. The specimens were subjected to preliminary microstructural tests using an optical microscope with Nomarski contrast and scanning electron microscopy. The tests showed a slight influence of the orientation of the samples on changes to the mechanical properties of the bimetallic sheets in the cyclic bending process. For samples oriented along the sheet rolling direction, discontinuities in the transition layer were found. The samples oriented perpendicularly to the rolling direction were free of this defect.

Production technology of steel three-layer bimetallic sheets at universal combined casting and deformation plant

An innovative technology for production of steel three-layered bimetallic sheets on the universal plant of the combined process of continuous casting and deformation is presented. The results of the stress-strain state of metal in the deformation centers when producing steel sheets and three-layered bimetallic strips on the unit are presented.

Effect of Step Size on the Formability of Al/Cu Bimetallic Sheets in Single Point Incremental Sheet Forming

Single Point Incremental Forming (SPIF) is an unconventional forming process that is suitable for prototype production and small lot production due to the economical tooling cost, short lead time, and the ability to create symmetrical and asymmetrical complex geometries without the use of expensive dies. This article presents the effect of the step size Δz of a forming tool made of 145Cr6 tool steel on the formability and maximum forming angle, mechanical properties, hardness, surface roughness, microstructure and texture of bimetallic Al/Cu sheets. Experiments were conducted at a constant rotational speed and feed rate, with the use of rapeseed oil as a lubricant. The tests were carried out with the use of a forming tool on both sides of the bimetallic sheet. The shape and dimensions of the formed elements are determined by non-contact optical 3D scanning. It has been proved that an increase in the step size Δz affects the deterioration of the surface quality of the specimens (an increase in the Ra parameter from 0.2 μm to approximately 3 μm for the step size of 1.2 mm), while a small step size down Δz favours the geometric stability of the samples. With increasing step size (at Δx = Δy = const.), the drawpiece wall continually thinned until the material fractured. Based on the results, it was shown that increasing the step size Δz over 1.1 mm causes cracking of the drawpieces. Furthermore, greater thinning of the Al/Cu sheet was observed in the range of step size Δz between 0.7 and 1.0 mm for aluminum side and step size Δz ≤ 0.6 mm and Δz ≥ 1.1 mm for copper side. It was also found that the mechanical properties of the bimetal sheet decreased as a result of incremental forming. The greatest decrease in strength and ductility was recorded for a pitch of 1.2 mm. Strength decreased from 230 MPa (for sheet in initial state) to approximately 80 MPa, elongation from 12% to approximately 8.5%, and hardness from 120 HV10 for Cu and 60 HV10 for Al to approximately 30 HV10 for both layers.

A novel Ni–Co–Al multi-principal filler wire for inhibiting Fe–Ti intermetallic compounds in welding CP-Ti/Q345 bimetallic sheets

In this work, a novel Ni–Co–Al multi-principal wire was used as only one type of filler material to finish the joining of TA1/Q345 bimetallic sheets by in situ preparation of high-entropy materials in the weld zone (WZ). The results indicated that a good weld formation could be achieved by using the Ni–Co–Al wire. The thermodynamic environment with high mixing entropy (ΔS mix) and low mixing Gibbs free energy (ΔG mix) in the WZ could be created by the Ni–Co–Al wire and the elements introduced from base metals. It could efficiently inhibit the formation of Fe–Ti IMCs and promote the solid-solution structures of FCC and BCC in the WZ. Fe–Ti IMCs were only presented in the transition zones on the TA1 flyer layer as well as a narrow region of the WZ within ∼30 μm away from the Q345/WZ interface, where the ΔG mix was higher than the ΔG of Fe–Ti IMCs.

Microstructure and properties of copper-steel bimetallic sheets prepared by friction stir additive manufacturing

Owing to their excellent mechanical properties, copper-steel bimetallic sheets are considered one of the best choices for preparing the plasma-facing components of the International Thermo-nuclear Experimental Reactor (ITER). However, due to the solid immiscibility between copper (Cu) and steel (St), it is hard to obtain desired interfacial bonding when using conventional fabrication processes, like rolling and explosive welding. In this work, Cu-St bimetallic sheets were fabricated by friction stir additive manufacturing (FSAM). Microstructural studies show that the wave-like interface with desirable joining was created between copper and steel. Mechanical tests present that the tensile strength and shear strengths are 435 MPa and 345 MPa, respectively. Such properties are remarkably better than that of other methods. Finally, the microstructure evolution and the relationship between microstructure and mechanical properties were discussed. These findings provide an effective way to regulate the interface engineering of bimetallic sheets.

Multi-Degree-of-Freedom Robots Powered and Controlled by Microwaves.

Microwaves have become a promising wireless driving strategy due to the advantages of transmissivity through obstacles, fast energy targeting, and selective heating. Although there are some studies on microwave powered artificial muscles based on different structures, the lack of studies on microwave control has limited the development of microwave‐driven (MWD) robots. Here, a far‐field MWD parallel robot controlled by adjusting energy distribution via changing the polarization direction of microwaves at 2.47 GHz is first reported. The parallel robot is based on three double‐layer bending actuators composed of wave‐absorbing sheets and bimetallic sheets, and it can implement circular and triangular path at a distance of 0.4 m under 700 W transmitting power. The thermal response rate of the actuator under microwaves is studied, and it is found that the electric‐field components can provide a faster thermal response at the optimal length of actuator than magnetic‐field components. The work of the parallel robot is demonstrated in an enclosed space composed of microwave‐transparent materials. This developed method demonstrates the multi‐degree‐of‐freedom controllability for robots using microwaves and offers potential solutions for some engineering cases, such as pipeline/reactors inspection and medical applications.

Analyzing metallurgical interaction during arc surfacing of barrier layers on titanium to prevent the formation of intermetallics in titanium-steel compounds

This paper considers a possibility to obtain high-quality butt junctions of bimetallic sheets from steel clad with a layer of titanium, with the use of barrier layers. The task that was tackled related to preventing the formation of Ti-Fe intermetallic phases (IMPs) between the steel and titanium layer. The barrier layers (height ~0.5 mm) of vanadium and copper alloys were surfaced by arc techniques while minimizing the level of thermal influence on the base metal. To this end, plasma surfacing with a current-driving wire and pulsed MAG surfacing were used. The obtained samples were examined by methods of metallography, X-ray spectral microanalysis, durometric analysis. It has been established that when a layer of vanadium is plated on the surface of titanium, a defect-free structure of variable composition (53.87–65.67) wt % Ti with (33.93–45.54) wt % V is formed without IMPs. The subsequent surfacing of steel on a layer of vanadium leads to the formation of eutectics (hardness up to 5,523 MPa) in the fusion zone, as well as to the evolution of cracks. To prevent the formation of IMPs, a layer of bronze CuBe2 was deposited on the surface of vanadium. The formed layer contributed to the formation of a grid of hot cracks. In the titanium-vanadium-copper transition zones (0.1–0.2 mm wide), a fragile phase was observed. To eliminate this drawback, the bronze CuBe2 was replaced with bronze CuSi3Mn1; a defect-free junction was obtained. When using a barrier layer with CuSi3Mn1, a defect-free junction was obtained (10–30 % Ti; 18–50 % Fe; 5–25 % Cu). The study reported here makes it possible to recommend CuSi3Mn1 as a barrier layer for welding bimetallic sheets "steel-titanium". One of the applications of the research results could be welding of longitudinally welded pipes of main oil and gas pipelines formed from bimetallic sheets of steel clad with titanium.

The butt of CP-Ti/304 stainless steel and CP-Ti/T2 bimetallic sheets using laser-induction heating welding technology

In this work, the CP-Ti/304 stainless steel (SS) and CP-Ti/T2 bimetallic sheets were implemented successfully using laser-induction heating welding technology without the Ti-Fe and Ti-Cu brittle intermetallics was formed in the joint. The CP-Ti of parent layer metal was welded by laser, the 304 SS and T2 of flyer layer metal were connected by induction heating welding. The induction heating welding have the advantages of only the BCuP-2 wire was melted with low heat input and the specimen of welding experiment was without heated. As the melt point of BCuP-2 wire was 710–800 °C, lower than the melt point of flyer layer metal 304 SS (1454 °C) and T2 (1083 °C) and the parent layer metal CP-Ti (1660 °C). When the process of induction heating welding, the parent and flyer layer metal was not melted and only the BCuP-2 wire was melted and filled the groove. Thus the dissimilar metals mixing was avoided completely, the Ti-Fe intermetallics without formed. The narrow transition layer was formed between the laser weld zone (WZ1) and the induction heating weld zone (WZ2) with the main structures of Cu, Cu3P and α-Ti. The joint was fractured at the WZ1 and the 304 SS side of WZ2 with a maximum tensile strength was ascertained to be 600 MPa.

Experimental investigation of butt welded Ti/steel bimetallic sheets by using multi-principal powders as a single filler metal

Owing to the easy-to-crack in the weld zones (WZ) of titanium alloy/steel bimetallic sheets, sequentially layered-to-layered welding, by using various filler metals, is widely adopted to join the bimetallic sheets. In this study, multi-principal filler powders of FeCoCrNiMn, as only one type of filler metal, were used to join TA1/Q345 bimetallic sheets by laser deposition welding. Microstructure evolution, microhardness, and tensile properties in the joint of TA1/Q345 bimetallic sheets were studied. The results indicated that TA1/Q345 bimetallic sheets could be joined by using multi-principal filler metal when the groove root was opened in the Q345 base plate. Significant transition zones were found at the TA1/WZ and Q345/WZ interfaces. The structures of α-Fe, β-Ti, β-Ti + TiFe, and α-Fe + TiFe2 were formed in the transition zones. The solidified primary phases of TiFe2 and the eutectic structures of α-Fe + TiFe2 were observed in most regions of the WZ. Various intermetallic compounds (IMCs) of TiFe and TiFe2, as well as the snowflake-like structures of TiC, coexisted in the WZ near the flyer and base layers, which were significantly harmful to the formability of the WZ and caused a crack in the WZ. The markedly high hardness and low tensile strength were presented in the WZ. A sawtooth-like fracture line was observed. The fracture line was extended from the WZ/base metal (BM) interface to the WZ center, in which the minimum hardness (∼523 HV0.2) and many eutectic structures were presented.