Vacuum Roll Research Articles

Effect of Nb interlayer on microstructure and property of Ti-6Al-4V/690 MPa grade steel clad plate by vacuum rolling

Ti alloy clad plate is of great interest for marine and petrochemical industry applications. However, high interfacial bonding is hardly obtained in the Ti alloy clad plate due to the brittle intermetallic compounds (IMCs) forming at the interface. In this study, a Ti-6Al-4V alloy/EH690 steel clad plate was fabricated by vacuum rolling and subsequently tempered to control the mechanical property of the steel substrate. The tempered sorbite appeared in the EH690 steel after quenching and tempering (QT). A decarburized zone, Fe2Ti + TiC mixed phases layer, and β-Ti layer were formed at the interface between steel and Ti. The brittle IMCs with high lattice mismatch resulted in a low interfacial strength of 108 MPa. To improve bonding strength, Nb was inserted between Ti and steel as an interlayer, which effectively inhibited the inter-diffusion of Ti, Fe, and C without brittle TiC or Fe-Ti IMCs. A (Ti, Nb) solid solution layer with high plasticity was present at the Nb/Ti interface. Fe2Nb and Fe7Nb6 phases were detected at the steel/Nb interface, exhibiting less brittleness and hardness compared to Fe-Ti IMCs. The interfacial shear strength was up to 265 MPa after adding the Nb interlayer, showing a mixed fracture mode of brittleness and ductility.

Microstructural evolution and properties of Ti/Al clad plate fabricated by vacuum rolling and heat treatment

Ti/Al clad plate is a highly promising material due to its low cost, lightweight nature, high strength, and excellent corrosion resistance. However, the deformation coordination between Ti and Al is very poor, and both metals easily are oxidated, resulting in a weak interfacial bonding. In this study, Ti/Al clad plate was fabricated by vacuum rolling, obtaining a clear interface without oxidation and compound. The as-rolled Ti/Al clad plate had a shear strength of 76 MPa with the fracture being at the Al substrate due to the solution of Mg2Si precipitates in the Al substrate during rolling. As a result, the solution and aging is necessary to enhance interfacial bonding. There were fine and dispersed Mg2Si precipitates in the as-treated Al substrate, and an (Al, Si)3Ti layer with ∼300 nm thickness appeared at the interface. Besides, the interfacial shear strength was up to 140 MPa, and the fracture still was at the Al side. The as-treated clad plate had an elongation of 33.5% which exceeded that of 25.8% calculated by the mixed rule. Obviously, the thin (Al, Si)3Ti layer is helpful to improve interfacial shear strength and plasticity of the Ti/Al clad plate.

PHYSICAL MODEL OF W AND Ti COMPOUND DURING HOT VACUUM ROLLING IN THE SOLID PHASE

The paper considers alternative methods for protecting metal surfaces from corrosion-erosion destruction (CED), based on galvanization or on the use of an oxide film. Their advantages and disadvantages are noted. For the manufacture of CED-resistant tungsten targets, which are used in the subcritical assembly created at the NSC KIPT, it is proposed to use the method of vacuum rolling of W and Ti. A layer of Ti serves as a protective coating. To describe the process of combining these metals, a model description is proposed, which is based on the use of the Rayleigh-Taylor dissipative instability theory (DRTI). An estimate of the values of the parameters of a binary metal system subjected to DRTI is given. The obtained characteristic bonding time of dissimilar metals corresponds to that observed in experiments.

Production of composite materials based on titanium and molybdenum by hot rolling

The production of composite layered materials from titanium and molybdenum, from titanium and molybdenum wire by hot rolling in vacuum is considered. The rolling conditions and the results of mechanical tests of the obtained composite materials are presented. Keywords: composite layered material, titanium, molybdenum, molybdenum wire, deformation, vacuum, package. kas_kktompim@dstu.ru, nurik909@mail.ru, fed40@yandex.ru

Effect of annealing process on the interfacial microstructure evolution and mechanical properties of 7050 aluminum alloy clad plates

• Aluminum alloy thick plates are produced by vacuum roll cladding technology. • The mechanical properties of the interface are improved by annealing treatment. • The Mg and O elements diffuse at the interface during the annealing process. • The Al 2 O 3 at the interface mainly evolves to MgO. In this research, aluminum alloy thick plates are produced by vacuum roll cladding (VRC) technology. And the annealing experiments with different annealing temperature and holding time are carried out for the clad plates. The results show that the tensile strength and elongation of the bonding interface are positively correlated with the annealing temperature and holding time. The fracture mode of the bond interface gradually changes from brittle fracture to ductile fracture. The Mg and O elements diffuse at the interface during the annealing process, and the Al 2 O 3 gradually evolves into MgO (mainly) and MgAl 2 O 4 . After holding at 470 ℃ for 24 h, the tensile strength of the interface is 427 MPa, which fully reaches the level of the matrix. Therefore, the dissolution and evolution of interfacial oxide contribute to the recovery of mechanical properties at the bonding interface.

Interface microstructure and bonding mechanisms of 7050 aluminum alloy thick plates produced by vacuum roll cladding

Vacuum roll cladding (VRC) based on friction stir welding (FSW) is applied to prepare aluminum alloy thick plates, and the effect of rolling reduction ratios (60%, 70%, 80%) on the microstructure and mechanical properties at the bonding interface of aluminum alloy clad plates are investigated. The results show that voids at the interface are gradually closed and the original interface finally disappears with the increase of rolling reduction ratios. There are 3 kinds of recrystallization mechanisms at the interface during hot rolling. The contributions to the healing of the interface are in the following order: geometric dynamic recrystallization (GDRX) > discontinuous dynamic recrystallization (DDRX) > continuous dynamic recrystallization (CDRX). At a rolling reduction ratio of 80%, GDRX characterized by the “pinch-off” of original grains mainly occurs at the interface, and no aggregation of defects and impurity elements is detected. The tensile shear strength and fracture displacement at the interface both reach the level of the matrix, which indicates that a good metallurgical bonding has been achieved at the interface. Therefore, the key to improving the interfacial healing quality is to break the interfacial oxide film and further induce recrystallization at the interface through a large rolling reduction ratio.

THE DEFORMATION VALUE EFFECT ON THE TA-W-TA SOLID-PHASE JUNCTION NATURE WITH INTERMEDIATE TI (TITANIUM) INTERLAYERS FOR THE NEUTRON PRODUCING TARGET OF THE NEUTRON SOURCE

The paper presents the quality studies results of the Ta-W-Ta solid phase junctions with Ti interlayers obtained by hot roll bonding in vacuum, that determine the work suitability in the form of neutron producing targets at the research nuclear facility ‘Source of Neutrons’. It is shown the layers mutual penetration level of the Ta-W-Ta solid-phase junction with Ti interlayers which provides a high level of clad layers adhesion when using the hot vacuum roll bonding method. The deformation parameters necessary both for the solid phase bond occurrence and for the reliable solid-phase junction formation of tantalum and tungsten refractory metals layers through a titanium interlayer, with a joint strength exceeding the value of a less durable material are determined. The possibility of chemical vapor deposition (CVD) method using for side faces coating of targets was studied.

Исследование влияния состава контролируемой газовой среды и температуры на качество твердофазных соединений проволок при изготовлении пористых сетчатых материалов

Porous mesh materials are designed for the manufacture of products with a given shape and size, as well as hydraulic, filtering, thermal and other properties. At the same time, they must have the necessary mechanical and technological properties, which are formed to a large extent by the quality of weld solid-state bonds of mesh wires. Findings of the research that the increase in the strength of wire bonds during manufacture of porous mesh materials is influenced by the conditions for removing oxide layers by means of choosing the optimal protective gas environment and heating temperature during welding. The analysis of the processes occurring at the boundary of the metal–oxide and oxide–gas phases made it possible to establish that, depending on the structure of the alloy, the heating temperature, the composition and partial pressure of the gas protective environment, not only additional oxidation or thinning of the oxide layers but also gas saturation of the work surface are possible. For the manufacture of sizeable sheet porous mesh materials with high accuracy in thickness, the use of welding by rolling in a protective gas environment is the only possible process. Depending on the chemical composition of the wires, it is possible to carry out mesh briquette rolling welding on vacuum rolling mills, in an argon atmosphere of controlled purity and in evacuated envelopes. Within the research, we studied the influence of the composition of the gas environment and the process temperature on the quality of weld bonds and found that it is advisable to manufacture VT2 alloy sheet porous mesh materials by hot rolling in a vacuum mill and in an inert gas environment with a controlled composition. Porous mesh materials made of 12Kh18N10T steel can be made by hot rolling in vacuum envelopes, and products with limited dimensions can be made by diffusion welding. The study also specifies the modes of technological processes for manufacturing porous mesh materials made of VT2 alloy and 12Kh18N10T steel by rolling welding and diffusion welding.

Variation in formation and migration of self-interstitial atom clusters in electron irradiated copper with material purity and specimen preparation method

ABSTRACT In situ observation with high-voltage electron microscopy was used to survey effects of impurity atoms on the formation and one-dimensional (1D) migration of self-interstitial atom (SIA) clusters in copper under electron irradiation at 300 K. Specimens were prepared from copper materials of five nominal purities (9N, 6N, 5N, 4N, and 3N) using three methods with different annealing conditions. In standard (STD) specimens prepared through cold rolling and annealing in vacuum, SIA cluster formation and 1D migration depended little on the nominal purity. In non-annealed (NA) specimens prepared from high-purity materials (9N and 6N) using mechanical processing and electropolishing, the defect structure was found to be coarser than in STD specimens. In fact, SIA clusters in NA specimens had number density of more than an order of magnitude lower and an average size more than four times greater. Furthermore, 1D migration had the frequency of about an order of magnitude higher and distance extending more than twice longer. Results of bulk annealing (BA) specimens showed that annealing of as-received block material had minor effects. Distributions of 1D migration distance for all specimens were described using an earlier proposed trap model. These results were discussed assuming that SIA clusters are trapped by impurity atoms existing in as-received materials and those induced by annealing.

Влияние предварительной химической обработки на качество твердофазных сварных соединений проволок при изготовлении пористых сетчатых материалов

Porous mesh materials with an organized structure, stable and reproducible properties are used in the manufacture of filter elements, thermal protection systems, rocket and turbojet engines, and other products with a given set of properties. The interlayer strength of such materials is significantly affected both by the modes of plastic deformation and welding and by the technology of preliminary chemical cleaning of the wire mesh surface. Etching work-pieces in a mixture of inorganic acids and organophosphorus complexones reduces the thickness of oxide films and additionally activates the contact surfaces in the welded joint. The study introduces the etchant solutions for treating VT1-0 titanium and corrosion-resistant 12Kh18N10T steel wires. The solutions increase the strength of the welded joints made by vacuum rolling welding and diffusion welding, compared with similar processes without pretreatment. The study also specifies the modes of technological processes of chemical etching and diffusion welding of 12Kh18N10T steel meshes, which provide maximum interlayer strength.

Комбинированные пористые сетчатые металлы и изделия из них

In this paper are considered the essence and design-technological features of products made from new types of porous mesh metals (PMM) based on combination of various permeable and impermeable metallic materials interconnected by hot rolling in the vacuum. To create new materials, a combination of different types of metal grids is used. Therefore, these materials have received the name - combined porous mesh metals (CPMM). The technological problem is to create reliable products with predictable strength, filtration and structural characteristics. The technology of manufacturing products from CPMM is complex and includes a large number of technological operations divided into operations for material manufacture and operations for manufacturing from this material a finished product of required application. Material production includes several operations for preparing the initial metal grids (washing, degreasing, marking-out, grid packaging), and complex technological operations for material manufacturing, consisting in joint the grids and embedded materials between themselves (vacuuming, heating to a predetermined temperature, grid package rolling in vacuum and in hot condition, etc.). Each of technological operations for material manufacturing should be carried out in rigid mode ranges, such as temperature mode, package drafting degree mode, etc. A slight deviation from the mode leads to rejected material or significant deviation from the specified parameters. A difficult problem is the interconnection of metallic grids of various types (distinguishing by thickness, wire diameter, etc.), as well as interconnection of solid metallic embedded elements necessary for products formation from the obtained material. As a result of numerous experiments, it has been able to achieve success and develop the technology for CPMM material manufacturing. The developed material and products made from it have been imbedded at the enterprises of those industries, where highly reliable and efficient constructions, made from permeable materials and having specified functional parameters, are required. A new phase separator filter (PSF) for the fuel tank (FT) of a space item has been created and implemented. Currently, sets including 20 typical sizes of PSF of various modifications are delivered. Using of capillary intakes (CIs) with PSF made from CPMM provides reduction of residual rests of fuel liquid components in fuel tanks. CIs with PSF are almost 2 times lighter than CIs, carried out according to traditional frame-grid design.

Influence of a Ni Foil Interlayer on Interface Properties of Mg-Clad Al Materials by Vacuum Roll Bonding

Influence of a Ni Foil Interlayer on Interface Properties of Mg-Clad Al Materials by Vacuum Roll Bonding

Sandwich Structure Electrode as Advanced Performance Anode for Lithium-Ion Batteries

In this work, a sandwich structure electrode was prepared by a simple vacuum filtration and rolling process. The SEM showed that the active materials were uniformly embedded in the pores of the three-dimensional conductive network of the carbon nanotube (CNTs) conductive paper. The contact interface area of active material and the conductive network significantly increased and the interface resistance was greatly reduced. The porous anode can accommodate the volume expansion of the silicon and effectively alleviated pressed during cycle. The electrode also exhibited good stability in cycles. Electrochemical tests showed that the first discharge specific capacity of the sandwich electrode reached 2330[Formula: see text]mAh/g with a coulombic efficiency of 86%. After 500 cycles, the specific capacity was still maintained at 1512[Formula: see text]mAh/g. At a large current density of 2[Formula: see text]A/g, the specific capacity hold was 840[Formula: see text]mAh/g compared with the copper foil electrode of 100[Formula: see text]mAh/g.

Bond characteristics of Al/Mg clad materials produced by vacuum roll bonding

The A1050/AZ31 clad materials were produced by vacuum roll bonding. The effects of rolling temperature and reduction rate on the interface of A1050/AZ31 clad materials were investigated, and the fracture behaviors of A1050/AZ31 interface were studied. A very thin intermetallic compound layer was formed at the A1050/AZ31 interface at rolling temperature of 350°C and reduction rate of 25%. Therefore the A1050/AZ31 interface mainly was ductile fracture, and the average tensile strength of A1050/AZ31 interface reached the maximum (43MPa). When the rolling temperature was 450°C and the reduction rate was 25%, the fracture occurred on the brittle intermetallic compound Al3Mg2 layer (thickness 7.68μm) and Al12Mg17 layer (thickness 1.95μm), mainly on Al3Mg2 layer, and the average tensile strength of A1050/AZ31 interface reached the minimum (0.61MPa).

Manufacturing Process and Interface Properties of Vacuum Rolling Large-Area Titanium-Steel Cladding Plate

In order to obtain large-area titanium-steel cladding plate by vacuum rolling, the manufacturing process was discussed with the Hypermesh/LS-DYNA simulation software. The result showed that the reduction rates of each rolling pass were 20, 25 and 33%, respectively. And the total rate was 60%. Moreover, the vacuum rolling process mainly included the following steps: welding preparation, drilling vacuum holes, composite and assembly, vacuum extraction, accumulative seal welding, preheating and rolling. The final size of the cladding plate was 1650 × 12000 × (4 + 40) mm. It could be found that the vacuum rolling interface of the titanium-steel cladding plate was mainly divided into four parts: steel layer (I), decarburized layer (II), bonding layer (III) and titanium layer (IV). Acicular widmanstatten structure of β-titanium was formed in zone IV, which might reduce the impact toughness of joint. The microhardness test results showed that the hardness near the interface was relatively high. Macroscopically, the average shear strength (297 MPa) and the average tensile strength (590 MPa) were both much higher than the standard. However, the brittle fracture mode of shear specimens might decrease the joint property of vacuum rolling cladding plate.

Application countermeasures of the manufacturing processes of titanium-steel composite plates

This study focuses on the application countermeasures of three kinds of manufacturing processes, namely Explosive Welding (EW), Explosive Welding and Hot Rolling (ER), Vacuum Rolling (VR) in order to further improve the technological level and provide support for the standardization production of titanium-steel composite plates. In this regard, the bonding properties of three kinds of titanium-steel composite plates were studied through microstructure observations and mechanical performance tests. Results showed that ER plate had nearly straight interface with unobvious undulations, while EW plate had wavy bonding interface and VR plate had straight clean interface. Moreover, EW plate, ER plate and VR plate had the diffusion layers of 6 μm, 33.5 μm and 21 μm, respectively. It was also obtained that the mechanical properties of VR plates were the finest, whereas the worst for ER plates. Meanwhile, the interface of VR plates showed low toughness. Based on the analyses of bonding properties, application countermeasures were obtained in the manufacturing processes of titanium-steel composite plates. Firstly, it was the best for titanium-steel composite plates with the flyer plate thinner than 2 mm that to be manufactured by VR and could also manufacture Category 0 composite plate like EW. Additionally, ER could be the priority process to manufacture low-bonding strength titanium-steel composite plates for its relatively low process cost. Finally, large-size titanium-steel composite plates should be fabricated by VR or ER because of the surface enlargement under rolling.

The Determining Role of Nb Interlayer on Interfacial Microstructure and Mechanical Properties of Ti/Steel Clad Plate by Vacuum Rolling Cladding.

We elucidate here the determining role of Nb interlayer on mechanical properties of Ti/steel clad plate fabricated by vacuum rolling cladding (VRC) as a function of different heating temperatures. A critical analysis on the clad interface via electron probe micro-analyzer, X-ray diffractometer and shear testing were conducted to investigate the influence of TiC, Fe-Nb and TiFe compounds and Nb-Ti solid solution on microstructural evolution and shear properties of Ti/steel clad plate. The inter-diffusion between Ti, C and Fe was effectively restrained by adding the Nb interlayer at heating temperature of 800 °C, and average shear strength of 279 MPa was achieved. With increase of heating temperature, Nb-Ti solid solution was formed at the Ti/Nb interface, which reduced mechanical properties of clad plate at 900 °C. At 1000 °C, TiC and Nb-Fe compounds and Nb-Ti solid solution were formed at the interface, and minimum average shear strength of 152 MPa was achieved. The detailed analysis on the clad interface suggested that ideal shear strength can be obtained through the addition of Nb interlayer and selecting appropriate heating temperature.

Effect of interfacial compounds on mechanical properties of titanium–steel vacuum roll-cladding plates

ABSTRACTThe titanium–steel clad plates were prepared by vacuum roll cladding. Ti–Fe compounds and TiC were observed at different cooling rates after rolling. Optical microscopy, electron microprobe analyser, X-ray diffraction and shear test studies were carried out to study the effect of Ti–Fe compounds and TiC on the ultimate microstructure and mechanical properties of titanium–steel clad plates. At a cooling rate of 6.2°C/min, TiC and Ti–Fe compounds seriously impacted the mechanical properties of the clad plate. At a cooling rate of 1.8°C/min, the thickness of the TiC layer was optimal much that the maximum shear strength of 296 MPa was obtained. At a cooling rate of 0.6°C/min, the thickness of the TiC layer was relatively thick, which affected the mechanical properties of clad plates.

Wave Processes and Mass Transfer on the Copper-Stainless Steel Interface under Solid Phase Bonding by High-Temperature Rolling

The paper presents the study of hierarchy of deformation wave-processes from nano- to macro-structural level, which takes place in dissimilar materials, bonded by high-temperature vacuum rolling in solid phase. The focus was on the processes that occur on the interface of the bonded materials: mass trasfer of impurities and alloying elements stimulated by deformation, the study of nano- and micro-hardness.

Effect of vacuum level on microstructure and mechanical properties of titanium–steel vacuum roll clad plates

Vacuum roll cladding (VRC) was used to bond pure titanium (Ti) plate to a plain low carbon steel (Q345) with the aim of obtaining a high-quality Ti–steel clad plate. The effect of interfacial compound on the microstructure and mechanical properties of Ti–steel clad plate was studied by electron probe microanalysis, scanning electron microscopy, X-ray diffraction and shear test. The clad plates were heated at 850 °C for 120 min and welded at different levels of vacuum. The results indicated that the cracked zone of the bonded interface decreased significantly with the increase in the level of vacuum during welding. Welding at atmospheric pressure, the randomly distributed TiN damaged the continuity of TiC and the uniformly diffused region of Ti and Fe at the bonded interface, while welding in vacuum of 1 × 10−2 Pa, maximum shear strength of 298 MPa was obtained because of the decrease in TiN content.