Bimetallic Sheets Research Articles

Research on the performance of laser-MIG arc tandem welding of CP-Ti/304 stainless steel bimetallic sheets

In this study, CP-Ti/304 stainless steel (SS) bimetallic sheets were prepared without the formation of Ti-Fe intermetallics in the joint. This required preparing a groove in the flyer and parent layer, and melting S211 wire using laser-MIG arc welding in tandem. The laser was used for the parent layer metal (CP-Ti) and the MIG arc was used for melting the S211 wire and filling the flyer layer groove. As the melting points of the parent layer metal CP-Ti (1660 °C) and the flyer layer metal 304 SS (1454 °C) were higher than the fill wire S211 (965–1035 °C), the parent and flyer layer metals were joined without melting. Liquid mixing of dissimilar metals was avoided and Ti-Fe intermetallics were not formed. The joint was observed to fracture at the laser weld zone and the right side of MIG arc weld zone, with a maximum tensile strength of approximately 680 MPa.

Experimental and simulated comparison of finite element models of bimetallic sheets for deep drawing process

In this study, different techniques used for modelling of bimetallic sheets by finite element (FE) method have been compared. Sheets modelled with five different assumptions were compared with each other and experimental data to determine the FE model that gives the most realistic result. FE models were created with the assumption that the adhesion was excellent or separable and with the case that the solidified adhesive in the intermediate layer was modelled and not modelled. As a result, the closest values to the experimental results were obtained with the model created with the assumption that there is a solidified adhesive layer in the middle layer and there is an adhesion interface between this layer and metallic layers. On the other hand, when the adhesive is not modelled in the middle layer, it has been observed that the solution time is reduced by 2.6 times while small changes are seen in the results.

Effect of heat input on interfacial characterization of the butter joint of hot-rolling CP-Ti/Q235 bimetallic sheets by Laser\u2009+\u2009CMT

Composite structures made of 2 mm-thick titanium and 10 mm-thick carbon steel are widely used in infrastructures such as long-distance gas transportation. However, cracking, which is caused by intermetallic compounds (ICs), is a dominate failure mode in welds of this structure. Thus, a common way to improve the in-service life of is reduce the number of ICs. In this paper, we employ a novel hybrid welding method to fabricate composite structures of TA2 titanium and Q235 carbon steel. Specifically, Ti and carbon steel is welded by laser and double Cold Metal Transfer (CMT) welding, respectively. The microstructure near the interface of Ti and steel is then examined using SEM, EBSD, EDS, with emphasis on the ICs in terms of chemical elements and morphologies. Results show that FeTi and Fe2Ti are the main ICs near the interface, and responsible for the failure of the welds. The effect of welding heat input on the formation of ICs is investigated as well. Results show that ICs are smaller when the heat input is low. Under low heat input circumstance, the tensile strength of the weld can reach up to 420 MPa.

Impact Of Strain Rate On Mechanical Properties Of Metallic Sheets At Various Temperatures

It is known that in warm and hot forming processes, the forming speed and with-it combined strain rate has immense role on material flow in bulk and sheet metal operations. In contrast, the influence of the strain rate on the flow curve has been rarely analysed at room temperature. This work analyses the influence of strain rate on flow curve of bimetallic sheets, Copper and Aluminium metals. Evaluation of the flow curve is carried out as a function of strain rate. In this work three different strain rates are considered for three different materials viz bimetallic sheets(Cu-Al), Copper and Aluminium. In addition to this ,the evaluation of flow curve at elevated temperatures is carried out. The Variation of mechanical properties with strain rate are plotted and analysed.

Microstructure Development in the Bonding Zone of Explosively Welded Ti and Cu Sheets

The interplay of various hardening and softening processes during explosive welding and post-processing annealing have been analysed in titanium/copper bimetallic sheets using scanning electron microscopy and microhardness measurements. Severe plastic deformation and intermetallics’ formation are typical processes leading to hardening, whereas dynamic/static recrystallization and the transformation of amorphous phases into crystalline ones lead to softening. In the as-welded state the interfacial layers of both parent sheets are severely deformed. However, they can undergo intense recrystalization in areas near large melted zones. Inside the melted zones a wide variety of chemical compositions can be detected, however, most of the phases do not appear in the Ti-Cu equilibrium phase diagram. The post-processing annealing at 973 K for 1 h leads to full recrystallization of severely deformed layers of parent sheets and transforms the non-equilibrium phases forming melted zone into the equilibrium TiCu4 and Ti3Cu4 ones via spinodal decomposition. Simultaneously, the growth of four intermetallic layers: Ti2Cu, TiCu, Ti3Cu4, TiCu4 situated along the whole interface was detected.

EXPERIENCE IN PRODUCTION OF LARGE-SIZE TITANIUM-STEEL BIMETAL FOR PIPE BOARDS OF NPP

The main provisions of modern technology for the production of bimetallic sheets for the manufacture of pipe boards for nuclear power plant condensers and nuclear icebreaker condensers are described. High quality in connection continuity and strength is provided by explosion welding in argon medium. The results of testing the properties of 216 bimetallic steel-titanium sheets are presented.

INCREASING OF RESOURCE OF SUPERCHARGERS' AND FANS' VEINS WITH WELDING METHODS

Influence of gas and dust stream's parameters on wear durability of protection elements (of veins and bearing disk) of fans and supercharges is analyzed. Data about wear pattern of the most charged details of labor devices, which are operated in conditions of thermal power and mining plants is given. The results of direct measurements of geometric dimensions' loss, the shape of blades and the bearing (central) disk were accounted until the moment of their replacement (renovation). Traditional measuring instruments and ultrasonic thickness gauge UT-31 were used. Beginning of wear with the smallest defects in the surface layer (irregularities, depressions, surface cracks, local bumps, etc.) is found. First of all, the inlet edge of the scapula on the side of the suction pipe is worn. The measurements of blade showed wear of the inlet edge to its complete destruction, blade decreased by 30 mm in length. In case of a two-layer structure, there is a «stripping» of base metal of the blade and further wear of the part is accelerated. The wear of the deposited layer up to 3 mm (25% of blade thickness) is critical for further operation. Considering the different mode of operation of the devices and the uneven nature of the wear, a differentiated approach is proposed when choosing the composition of the metal for hardening and facing of the most worn surfaces. As reserves for increasing of inter-repair periods, arc surfacing with adding of different carbide-forming agents (in unequal amounts by zones) and using of surfaced bimetallic sheets are named. Spherical granules of tungsten carbides instead of crushed particles and the working bimetal layer molded in composition as durable high-chromium cast iron are recommended for reinforcement.

Microstructures and performances of the butt joint of TA1/Q235B bimetallic sheet with addition of a Mo interlayer by using narrow gap laser welding with filler wire

By taking molybdenum (Mo) having favorable metallurgical compatibility with both titanium and iron as the interlayer material, the butt joint of TA1/Q235B layered bimetallic sheet with thickness of 6 mm was prepared by utilizing narrow gap multi-pass laser welding with low heat input. Mo generally can favorably isolate Ti from Fe, meanwhile the transition zone of Mo and steel adjacent to Mo interlayer was softened according to the results of microhardness test. The results of face bending testing showed that the softened zone was beneficial to the mechanical properties of the welded joint, which could restrict the crack propagation along the interface of Mo/steel in fusion zone so that fracture appeared in the BM side. The microstructures of the softened zone exhibited a low dislocation density observed by a transmission electron microscope (TEM), which may be the main reason leading to a low microhardness. In additon, Mo interlayer was confined in a small zone, which only accounted for about 6.5% of the total area of cross section of the fusion zone while a small amount of FeTi and λ brittle intermetallic compounds (IMCs) still appeared around the Mo/steel interface in fusion zone. The tensile strength of the welded joint was 467 MPa, which took up about 93% that of base metal. The results of this paper will help guide endeavours for the fabrication of pipes and containers made of Ti/steel bimetallic sheets.

Towards a better understanding of the phase transformations in explosively welded copper to titanium sheets

The influence of post-process annealing on the growth kinetics of the intermetallic phases and mechanical properties of titanium/copper bimetallic sheets were analysed using scanning and transmission electron microscopies, X-ray synchrotron radiation, and mechanical testing. In order to weld two metal sheets, an explosive welding technique was utilised. Subsequently, the clads were subjected to post-weld annealing at 973 K from 0.25 to 1000 h. In the bonded state, the interface exhibited a wavy structure with only a small amount of solidified melt zones, composed of non-equilibrium phases of variable chemical compositions. After short annealing times (<1 h) these non-equilibrium phases transformed into equilibrium phases of TiCu4 and Ti3Cu4via spinodal decomposition. For longer annealing times (>1 h), the growth of four intermetallic layers: Ti2Cu, TiCu, Ti3Cu4, and TiCu4 situated along the entire interface is predominant. It was observed that the phases enriched with Cu and Ti were situated near the Cu and Ti parent sheets, respectively. The nano-hardness of the intermetallic phases decreased as the Ti content increased, whereas the Young's modulus reached its highest values for phases with equiatomic or close-to-equiatomic composition.

Interfacial reactions and structural properties of explosively welded titanium/copper plates

In this study, the effect of post-processing heat treatment on the interface morphology and kinetics of intermetallic phase growth in titanium/copper bimetallic sheets were analyzed using a scanning electron microscopy and mechanical testing. Ti/Cu composite was fabricated by explosive welding. Then, clads were subjected to the post-welded annealing at 973 K for times ranging between 15 min and 100h. In the as-bonded state, the interface shows a wavy character with a limited number of melted zones, which are mostly composed of phases that are not observed in the Ti-Cu equilibrium phase diagram. Short-term annealing is shown to transform non-equilibrium phases into equilibrium ones, such as TiCu4 and Ti3Cu4. For longer annealing times, the growth of four intermetallic sublayers (Ti2Cu, TiCu, Ti3Cu4, and TiCu4) distributed along the entire interface is detected. However, the growth kinetics of particular sublayers was different. Volume fraction estimation of intermetallic phases at annealing times under study revealed the largest thickness for TiCu and TiCu4 phases. The nano-hardness of intermetallic sublayers was found to drop with the Ti content.

A Composite Joint Based on Two Kinds of Connection Mechanisms for TA2/T2 Bimetallic Sheets by Laser-TIG Hybrid Weldings

The possibility of two pass welding for TA2/T2 bimetallic sheets joint with laser-TIG hybrid weldings was studied. Laser-gas tungsten arc welding (TIG) hybrid welding of TA2/T2 bimetallic sheets has been applied using BCuP-2 wire as filler metal. A new welding process for TA2/T2 butt joint was introduced on the basis of the controlling the formation of Ti-Cu intermetallics in the joint. One process was two pass welding involving creation of a joint with one laser weld and one TIG weld separated by remaining unmelted TA2/T2 interface. When laser beam on the TA2 side junction surface, T2 would not be completely melted in joint. When TIG welding in groove, the filler metal melted occurred at the TA2 and T2 interfaces. Through two pass welding, the the formation of Ti-Cu intermetallics can be completely avoided during welding. In the paper, microstructure and mechanical characterization of Ti/Cu clad plates laser and arc welded joints were carried out. The unmelted part of TA2/T2 explosive interface acted as a diffusion barrier between Ti and Cu. The unmelted TA2/T2 explosive interface was beneficial to relieve and accommodate the thermal stress. The joint fractured mainly at the brazed weld with the maximum tensile strength of 610 MPa.

Warping of a Stretched Bimetallic Sheet

The development of bimetallic materials is one of the modern lines of research. The differences in the properties of components can impart special mechanical characteristics to the material, which provides its most effective functioning in different fields of application. The stretching deformation mechanism of a Cu-Al sheet was set, and a calculation model of warping deformation was constructed, which relates the warping angle with governing factors. In research, advanced 3D image processing equipment was used. The proposed parameter is similar to Poisson’s ratio in describing the end-use and intrinsic properties of bimetallic sheets.

Network-Selectivity, Magnetism, and Proton Conduction of 2-D and 3-D Metal-Organic Frameworks of the Constituents {P(CH2OH)4}+/MII (MnII, FeII, or CoII)/[CrIII(ox)3]3.

Two types of metal-organic frameworks (MOFs), including {P(CH2OH)4}6[MnII3{CrIII(ox)3}4]·10H2O·2EtOH (1) and {P(CH2OH)4}[MIICrIII(ox)3]·H2O (M = Fe (2), and Co (3)), are selectively formed by a reaction of {P(CH2OH)4}Br, MCl2, and (NH4)3[Cr(ox)3]. 1 has the 3-D anionic framework, [Mn3{Cr(ox)3}4]n6n-, consisting of the Mn4Cr4 octagonal and Mn6Cr6 dodecagonal channels, in which {P(CH2OH)4}+ ions and the solvation molecules (H2O and EtOH) are accommodated. 2 and 3 have a 2-D network of oxalate-bridged bimetallic sheets with an intercalation of {P(CH2OH)4}+ ions. Magnetic studies revealed ferromagnetic ordering in all the MOFs, with TC = 5.6 K for 1, 10.6 K for 2, and 12.2 K for 3. The {P(CH2OH)4}+ ions in the MOFs promote proton transfer via the vehicle mechanism, which gives rise to a significant room-temperature conductivity of 1.03 × 10-4 S cm-1 at 70% RH for 1, 4.60 × 10-6 S cm-1 at 60% RH for 2, and 3.04 × 10-5 S cm-1 at 70% RH for 3.

Effect of current on microstructures and properties of tin bronze/steel bimetallic sheets fabricated by arc deposited technique

Tin bronze/steel bimetallic sheets were prepared via fabricating the tin bronze cladding layers on the thin steel sheets using cold metal transfer arc deposited technique. The effect of current intensity on the morphologies, microstructures and mechanical properties of the tin bronze/steel bimetallic sheets were analysed. Under the current intensity of 60–90 A, there were no pores, iron-rich particles and oxide phase in the cladding layers, and the dilution rate was almost zero. The cladding layers were composed of primary α-Cu phase and intergranular structures including (α-Cu + δ-Cu41Sn11 + Cu3P) ternary structure and (α-Cu + Cu3P) binary structure. The hardness distribution was uniform at different locations in each cladding layer, and the strength of bimetallic sheets was higher than original thin steel sheet. Under the current intensity of 100-110 A, pores appeared in the cladding layers and the grain morphologies changed into petal shape. Iron-rich spherical particles and Fe3P particles were formed in the cladding layers, and the fusion layers appeared at the interface between cladding layers and thin steel sheets. The bimetallic sheets had drastic reduction in strength and elongation as the current was 110 A.

Determination Of Formability Of Bimetallic Sheet Using Forming Limit Diagram

Abstract The Formability of a sheet plays an important role in all sheet metal forming operations. It is required to determine the formability of sheet to know the behavior of the sheet under various loading conditions. By determining the formability, it will be easier to predict the failure point of a sheet metal. Further it suggests us the maximum permissible value of load to be applied on the sheet material so that it will not fail. Forming Limit Diagram is a graphical way of depicting the forming behaviour of a sheet metal. FLD estimates various regions of sheet metal of plastic deformation and suggests a permissible value of load to be applied. However FLD of Aluminium, MS, Copper etc are known from the record books but FLD for bimetallic sheet is not yet determined. Bimetal refers to an object that is composed of two separate metals joined together. Instead of being a mixture of two or more metals, like alloys, bi-metallic objects consist of layers of different metals. Generally, these bimetals are used for thermal applications like the thermostat, thermocouple and other electrical devices which need circuit breakers. But these bi-metallic sheets have better strength, thermal resistance and ductility than the singular sheet metal. Hence, the aim of this work is to determine whether these bi-metallic sheets are suitable for deep drawing operation or not. This can be determined by finding out the formability of these sheets. The main objective of this work is to draw the Forming Limit Diagram of bimetallic sheet made of Aluminium and Copper and to find the formability of the sheet. To achieve this objective the strength of the bimetallic sheet is determined first and then Chemical Etching of the bimetallic sheet is done which creates a grid pattern of circles on the surface of the sheet. The sheet is then cut into different widths by keeping the height of the specimen constant. Erichsen cupping test is performed for different widths of bimetallic strips. During the experimental process the sheet is initially fixed between die and punch. Then the punch is made to advance through specimens until a fine hair line fracture appears. The circles on the surface of the sheet will be deformed into ellipse. Deep drawing is carried out for the same bimetallic sheet where the blank of the bimetallic sheet is drawn into cup. The major and minor axes of the ellipse which corresponds to major and minor strains are measured. The strains are measured along different portions of the cup namely flange portion, side walls and the base of the cup and this is included in the Forming Limit Diagram of Bimetallic sheet. By taking major strain on Y-axis and minor strain on X-axis, a curve is obtained which is called as Forming Limit curve or Forming Limit Diagram.

Experimental study on bending behaviour of aluminium-copper clad sheets in V-bending process

The bimetallic sheets are used in the industrial sheet metal products to meet the demands of multi-functionality. The bending behaviour of bimetallic sheet is contributed by individual layers of the sheet and it is entirely different from the monolithic material. In this study, V-bending experiments are carried out to understand the springback, bend force and thickness change of Al-Cu clad sheets. The effect of different parameters such as sheet thickness, sheet setting condition, die angle, die opening and punch radius have been investigated. The results indicated that springback is more for smaller die angle, wider die opening and larger punch radius. Increase in die angle, increase in die opening or decrease in punch radius decreases the bend force. The clad sheet thickens at Al/Cu setting condition whereas it thins at Cu/Al setting condition. This thinning or thickening of the sheet influences the springback and bend force.

Influence of tool geometry on material flow and mechanical properties of friction stir welded Al-Cu bimetals

Al-Cu bimetallic sheets were friction stir welded by three different kinds of pin profiles (threaded cylindrical, threaded conical and pyramidal). Among the three pin geometries used, the threaded conical tool provided the best compromise between the different material flow regions and thereby the fewest defects and the highest weld strength were obtained with this tool. As the cylindrical tool has the lowest contact area, it resulted in insufficient material flow around the pin and tunnel defects appeared on the advancing side. A downward material flow is essential to avoid tunnel defects on the advancing side. It was not possible to obtain a weld efficiency of one hundred percent due to the existence of a micro-void analogous to kissing bond on the retreating side. This flaw is a result of a downward material flow, which is essential to obtain a defect-less weld on the advancing side. Torque values and temperatures during welding were directly related to the downward material flow. In samples without tunnel defects on the advancing side, higher values of torque and temperature were recorded.

Effect of rotational speed on friction stir spot welding of AA5052-H32/HDPE/AA5052-H32 sandwich sheets

Friction Stir Spot Welding (FSSW) of AA5052-H32/HDPE/AA5052-H32 sandwich sheets is performed at six different tool rotational speeds to evaluate the optimum range. The mechanical performance, hook formation, grain size, hardness and temperature distribution are evaluated. Lap shear test, cross tension test, peel test and uni-axial tensile test are conducted. A comparative assessment has been made between the bimetallic and the sandwich sheets after FSSW. The optimum rotational speed for joining the sandwich sheet is 1800rpm and beyond, where the joint strength and extension to failure are found to be acceptable. In hook formation, two hooks are prominently seen in the sandwich sheets, while it is only one hook in the bimetallic sheets. The hook width increases and the hook height decreases with increase in rotational speed. A mechanism has been proposed to explain such phenomenon. The peak temperature increases with increase in rotational speed and it gets reduced in sandwich sheet as compared to bimetallic. The polymer layer takes a part of the heat flux during stirring to reduce the peak temperature in sandwich system. The bimetallic joints are stronger than sandwich sheet joints showing better joint strength and extension at failure in almost all the tests. Joint hardness distribution supports such performance. Nugget pull-out and partial nugget failure are observed during joint failure of sandwich sheets.

Increased quality and welding efficiency of laser butt welding of 2205/X65 bimetallic sheets with a lagging MIG arc

2205/X65 bimetallic sheets were butt welded by a fiber laser with single pass based on flow behavior of molten pool in full penetration welding processes. Optimal welding parameters were defined based on experiments using orthogonal arrays design to ensure highest relative independence of the upper and lower fusion zones (FZ). Balance of ferrite and austenite was found to be completely disrupted. To counterbalance excess α-ferrite formed in the lower fusion zone, laser-Metal Inert Gas (MIG) tandem welding was introduced for butt welding of 2205/X65 bimetallic sheets. Microstructures and corrosion properties of welded joints were investigated using optical microscopy, scanning electron microscopy (SEM) and potentiodynamic tests. Metallographic observations indicated that MIG arc followed the rear of laser beam reheated the laser weld in the front. This resulted in increased austenite nucleation and growth in the FZ region of the flyer layer. Thermal power of MIG arc and laser arc distance were important factors, which affected grain size and alloy element content in ferrite and austenite. Potentiodynamic tests indicated that the FZ consists of fine grains with increased corrosion resistance, which was close to the parent metal exposed to chloride solution.

Investigation into the effect of material properties and arrangement of each layer on the formability of bimetallic sheets

The application of bimetallic sheets composed of two dissimilar sheet metals with distinct properties has increasingly developed in recent years. Enhancement of bimetallic sheet’s formability by designing of appropriate layers is an important challenge for industrialization of these sheets. The main objective of this paper is investigation on the influence of material properties of layers on the formability of bimetallic sheets analytically and experimentally. The analytical model was developed to predict forming limit diagram (FLD) based on M-K model using both the Hill’s and Barlat-Lian yield functions. The experimental works was performed on Aluminum (AL3105)/Carbon steel (St14) sheets for verification of analytical model. Results showed that the formability of bimetallic sheet is enhanced by increasing of the strain hardening and strain rate sensitivity exponents of layers, although variation of the exponent coefficient of the layer with higher formability was more effective than layer with lower formability. In addition, the results demonstrated a significant nonlinear effect of variation in thickness of layers on the FLD0 index. It is found that the influence of anisotropy coefficient of layers is negligible in comparison with other material parameters, but the arrangement of anisotropic steel layer with isotropic aluminum layer as well as the arrangement of layers in the aligned rolling direction (0°−0°) can slightly improve the formability of two-layer sheets.