Alloy Vacuum Research Articles

Exploration of deep purification of aluminum alloy in vacuum based on adsorption of oxides by hydrogen bubbles

This study proposes a purification method for aluminum alloys based on vacuum and stirring. The data shows that when the vacuum degree ranges from -10 Pa to -1000 Pa and the stirring speed of the melt varies between 30 rpm and 50 rpm, the hydrogen content in the alloy fluctuates slightly around 0.099 cm3/100g, while the oxygen content fluctuates around 24 ppm. Compared to the alloy under other processing conditions, the hydrogen and oxygen content in the alloy at this time are the lowest. Furthermore, compared to the untreated alloy, the purified alloy showed significant improvements in mechanical properties. The tensile strength and elongation of the alloy reach 200.1 ± 4.3 MPa and 0.71 % ± 0.02 %, respectively. The changes in mechanical properties are related to the decrease in hydrogen content and oxide reduction in the melt. Stirring generates bubbles in the melt, which adsorb oxides from the melt. Subsequently, vacuum causes these bubbles to expand. These expanded bubbles can rapidly absorb hydrogen in the melt. When bubbles with oxides rise to the melt surface, the melt is purified to a certain extent. Additionally, the attachment of oxides to the bubbles is observed through transmission electron microscopy.

Initiation and propagation mechanism of fatigue crack in ultra-thick titanium alloy vacuum electron beam welding joint

The investigation delved into the fatigue properties across various layers of joints in a 130-mm-thick Ti6Al4V- damage tolerance titanium alloy, which had been fabricated through vacuum electron beam welding. Microstructures in welds are inhomogeneous along the thickness direction of joints. The fatigue properties of various layers of joints exhibit minimal differences, with the fatigue limit consistently exceeding 90 % of the base metal. The cracks always initiate on the sample surface, with numerous fatigue striations present on all fractures. Additionally, many dimples are observed in all fracture zones. The fatigue crack propagation mechanism is depicted as a series connection of micro-pores. Micro-pores are formed by inward pitting of material surfaces and nucleate in local plastic deformation zones of the material. Stress concentration of microstructures is an important cause for formation of local plastic deformation zones. After high cycle fatigue experiments, martensite lath-shaped α′ phase in microstructures in the weld is broken and the broken α′ phase pins the dislocations, resulting in microscopic stress concentration.

Enhancement in interfacial bonding quality of CoCrFeMnNi high-entropy alloy vacuum hot-compression bonding via surface shot peening

Vacuum hot-compression bonding (VHCB) is an advanced solid-state bonding technique. To expand its application in high-entropy alloys (HEAs), a new strategy to enhance the interfacial bonding quality of CoCrFeMnNi HEA VHCB joints by surface shot peening (SP) was proposed, and the effects of SP treatment on the interfacial bonding behavior and mechanical properties of VHCB joints were investigated. The results revealed that SP treatment introduced a nanocrystalline layer and plastic deformation layer with non-uniform strain on the specimen bonding surface, and a hierarchical grain size gradient fine microstructure was formed by a static recrystallization process under the thermal activation condition before VHCB. During the bonding process, the fine microstructure of the SP-treated layer was retained and provided a large number of grain boundaries and dislocations, which facilitated atomic diffusion and plastic flow in the interfacial region and promoted the closure of interfacial voids and the dissolution of interfacial oxide particles. Additionally, interfacial crystallographic and tensile test analyses indicated that the SP treatment induced a multiple interfacial grain boundary (IGB) migration mechanism in the VHCB joints, which dramatically improved the IGB migration level and ultimately led to a complete recovery of the mechanical properties of the CoCrFeMnNi HEA VHCB joints.

Effects of different scanning speeds on microstructure evolution and tribological properties of Inconel 718 alloy vacuum electron beam surface modification

In this paper, based on vacuum electron beam surface modification technology, the surface modification experiments of electron beams on Inconel718 plates at different scanning speeds (180 mm/min, 240 mm/min, 300 mm/min, 360 mm/min and 420 mm/min) were studied. The microstructure evolution law and friction and wear properties of electron back scatter diffraction (EBSD) and friction and wear testing machine RTEC (MFT-5000) were analyzed. Then, SEM and EDS were used to study the friction and wear mechanism. The results show that the microstructure of Inconel 718 sample after electron beam surface treatment is divided into basis material (BM), central zone (CTZ) and column zone (CLZ). The grains in the BM region are equiaxial, the grains in the CTZ region are fine strips, and the CLZ region is dominated by short coarse grains. After electron beam treatment, the annealed twins inside the specimen are eliminated, and when the scanning speed is 300 mm/min, the recrystallization ratio is the largest and the orientation difference becomes the most uniform. Different recrystallization textures appeared in different scanning speed specimens, and the textures in the original state are concentrated on copper{112}<111> and S{123}<634 > textures. After electron beam treatment, the texture of the specimen is mainly concentrated in the cubic texture. Experiments have shown that electron beam surface treatment can reduce oxidative wear and adhesive wear of specimens. When the scanning speed is 300 mm/min, the wear volume is the smallest, the wear resistance is the best, and the wear rate is reduced by about 15 % compared with the original specimen. Electrochemical corrosion experiments demonstrated that the relative corrosion rate of Inconel 718 was 1.3 times higher than that of the selected electron beam clad specimens.

Chemically dealloyed Mg–Cu alloy lamina as an interlayer for reinforcing a C/C composite – TC4 alloy vacuum brazed joint

Here, a novel brazing interlayer of bicontinuous nanoporous copper (NP–Cu) lamina was produced by chemically dealloying a magnesium-copper (Mg–Cu) binary alloy and applied for brazing a C/C composite and TC4 alloy along with AgCuTi alloy brazing filler. SEM, EDS, XRD, XPS, TEM and SAED were used to characterize the differences in microstructure and phase distribution of the samples and compare with samples without an interlayer. Mechanical testing in the form of shear tests were conducted to evaluate the change in shear strength caused by the interlayer. The large specific area, uniform nano scale porosity and ligaments of the NP-Cu lamina interlayer induced the transformation of Ti–Cu compounds from their bulk agglomerates to dispersed fine particles and formed eutectic phases, which contributed to relieving the residual stress and enhancing the plasticity of the joint seam. This led to a shear strength increase of 185% as compared to samples without an interlayer.

Effect of the various tritium breeding materials on the tritium breeding ratio in ARC fusion reactor

This study deals with TBR (Tritium Breeding Ratio) performance of the four different types of molten salt (FLiBe, FLiNaK, FLiNaBe, FLiNaRb) which has four different Li-6 enrichment ratios (0%, 30%, 60%, 90%) Moreover, two different vacuum vessel materials (SiC composite and V4Cr4Ti alloy) have been used in ARC reactor geometry. In models with TBR ≥1.05, it has been desired to examine the sustainability of the tritium production of the reactor by removing the neutron multiplication layer from the design without using the toxic Beryllium element. The neutronic performance studies have been examined in OpenMC, which is an open-source Monte Carlo neutron and photon transport code. The TBR values of the different models obtained and the change of these values according to Li-6 enrichment were examined. Obtaining result showed that the FLiBe molten salt and V4Cr4Ti alloy vacuum vessel wall material could be the best choice for the ARC reactor.

Processes of formation of Cu–Ni alloy films by electron beam evaporation

The features of the formation of Cu–Ni alloy films by electron beam evaporation are considered. The position of the isobars of the total pressure of copper and nickel on the state diagram of the Cu–Ni during evaporation in vacuum is determined. Calculations of the elemental compositions of films have been carried out. It is shown that the nickel content in films deposited during boiling of Cu50Ni50 alloy in vacuum is 50 times less than in the alloy. The structure and elemental composition of the surface layer of alloys after their evaporation and sublimation, as well as the elemental composition of the deposited films, are investigated. It is shown that the most acceptable way to obtain films of stable composition in the Cu–Ni system is simultaneous electron beam evaporation of copper and nickel from two crucibles.

Study on Microstructures and Properties of the Al. Alloy Vacuum Die-Cast Parts of TL117 and C611

The microstructures and properties of the vacuum die-cast Al. alloy C611 were studied by taking the vacuum die-cast Al. alloy TL117 as a reference. The purpose is to cancel the T6 heat treatment and part correction process in the die-cast Al. alloy production in order to reduce the cost of parts. By adding rare earth element Sr, the crystallization process and crystal morphology can be controlled, by which the grains can be refined and the phase transformation stress can be controlled properly. The strength and deformation of the part can meet the design requirements. By comparing the microstructures, second phases, strength, elongation, fracture morphologies and crystallization latent heat of the two materials, the mechanisms of high performance and small deformation of the C611 part were obtained. The research of the vacuum die-cast Al. alloy without heat treatment and correction is of great significance to the application of Al. alloys in automobile field.

Joint Low-Temperature Carbothermic Synthesis of WC-Co Alloy in Vacuum

A new method for obtaining submicron hard alloys based on sintered tungsten carbide with cobalt by joint low-temperature carbothermic synthesis in vacuum has been developed. The compositions of the initial components for the synthesis of powders of the composition WC-6%Co and WC-10%Co are calculated. The main component for the synthesis of submicron tungsten carbide powders is tungsten oxide WO2.9, obtained by reducing α-tungsten oxide WO3 in a hydrogen medium at a temperature of 500-550 °C. The powders obtained by synthesis are characterized by high hardness values (up to 94 HRA). Cutting tests of replaceable polyhedral plates made from the obtained powders for processing a heat-resistant alloy have shown satisfactory results. The microstructure of the alloys was analyzed using scanning electron microscopy.

Effect of ultrasonic surface rolling process on the surface properties of CuCr alloy

A nanocrystalline surface layer was fabricated on the surface of CuCr8 alloy by surface ultrasonic rolling treatment (USRT) with different rolling depth. The surface morphology, microstructure, hardness, surface strength and corrosion resistance were systematically characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the corresponding test methods. The results showed that the USRT treatment did not change the surface phase of the CuCr8 alloy, but only refined the surface grain. The rolling depth had great influence on the surface properties of the CuCr8 alloy. When the rolling depth was 0.15 mm, the surface comprehensive performance was the best. The surface grain size was about 78 nm, the surface hardness was up to 120 HV0.05, the tensile strength reached to 400 MPa, and the corrosion performance was significantly enhanced. The content of Cr, CuO and Cu(OH)2 in the passivation film of the USRT treated alloy was higher than that of the CG alloy. The USRT treatment provides a new method for fabricating CuCr alloy vacuum break tubes with high surface properties.

Neutron diffraction study of concentration phases transition in the TiC0.50Hy alloy

The study belongs to the field of hydrogen materials science. A neutron diffraction study of titanium carbohydride TiC0.50Hy was carried out in the range of hydrogen concentration у = 0.50 ÷ 0.60. It is shown that high-temperature titanium carbohydride TiC0·50H0.50 of equiatomic composition has a face-centered cubic lattice (sp. gr. Fm3¯m), where hydrogen atoms are located in tetrahedral interstices. It has been established that in this alloy in vacuum, the phenomenon of hydrogen thermal emission is observed - complete removal of hydrogen with preservation of the FCC lattice of the TiС0.50 interstitial alloy. For the first time in the Ti–C–H system, a first-order concentration phase transition FCC (sp. gr. Fm3¯m) → HCP (sp. gr. Pm3¯1) in TiC0.50Hy carbohydride at a hydrogen concentration y > 0.50 was discovered without changing the octahedral environment of carbon atoms and tetrahedral the surroundings of hydrogen atoms by Ti atoms. The HCP phase in vacuum is heat-resistant at temperatures T < 600 K. The unit cell volume of the hcp phase is two times smaller than the unit cell volume of the FCC phases TiC0.50Hy and TiH2 of equiatomic composition. The results of studying the fcc phase of the equiatomic composition of TiC0·50H0.50 can be used to prepare a high-temperature hydrogen reservoir in hydrogen energy. The HCP phase can be used as a biological protective material in transport nuclear power plants and on nuclear submarines instead of titanium dihydride TiH2.

Effect of bonding temperature and heat treatment on microstructure and mechanical property of Mg−6Gd−3Y alloy vacuum diffusion bonded joints

Diffusion bonding of as-cast Mg−6Gd−3Y magnesium alloy was carried out at temperatures of 400−480 °C with bonding pressure of 6 MPa for 90 min. Diffusion bonded joints were solution treated at 495 °C for 14 h and then aged at 200 °C for 30 h. Microstructures and mechanical properties of joints were analyzed. The results showed that rare earth elements and their compounds gathering at bonding interface hindered the grain boundary migration crossing bonding interface. Tensile strength of as-bonded and as-solution treated joints increased firstly and then decreased with the bonding temperature increasing due to the combined effects of grain coarsening and solid-solution strengthening. As-bonded and solution-treated joints fractured at matrix except the joint bonded at 400 °C, while aged joints fractured at bonding interface. The highest ultimate tensile strength of 279 MPa with elongation of 2.8% was found in joint bonded at 440 °C with solution treatment followed by aging treatment.

The high temperature corrosion of Incoloy 800H alloy at three different atmospheres

ABSTRACT Incoloy 800 H alloy is one of the candidate materials for high-temperature gas-cooled reactor steam generator heat transfer tubes. Previous studies have shown that corrosion phenomena such as oxidation and carburization occurred in high-temperature impure helium gas. On this basis, the corrosion behavior of Incoloy 800 H alloy in air, impure helium, and vacuum was investigated. After the experiment, electronic balance, scanning electron microscope, X-ray energy spectrum analysis, X-ray diffraction analysis, and gas chromatograph were used to characterize the corrosion behavior of the alloy. The results showed that CO is the main oxidation and carburization gas of Incoloy 800 H alloy in impure helium. Contents in ppm CO2 can supplement the reduction of CO and prevent the destruction of oxidation layer and carburization layer; The mass change of the alloy after corrosion in air at 950°C met the oxidation parabola law, the corrosion layer on the alloy surface fell off, and Si migration and accumulation in different degrees occurred in air and impure helium experiments; Carbon transfer and decarburization occurred in the alloy in a vacuum.

The high temperature oxidation behavior of IN718 alloy in vacuum

Deformation bonding is a highly promising process to make homogenized large ingots. Although performing in vacuum, the oxidation at bonding interface is inevitable. This work investigates the oxidation behavior of IN718 in vacuum. The initial oxide scale is composed of an inner layer of δ * -Al2O3 and an outer layer of anatase-type Ti1−xAlxO2 with rutile-type Ti1−xNbxO2 particles at their oxide/vacuum interfaces. With the increase of oxidized time, oxides tend to decompose and transform. The stable order is rutile-type Ti1−xNbxO2 ＜ anatase-type Ti1−xAlxO2 ＜ rutile-type TiO2 ＜ δ * -Al2O3 ＜ α-Al2O3. Preferential oxidation of MX, MX/matrix interface and grain boundary are also discussed.

ВЗАИМОДЕЙСТВИЕ ХИМИЧЕСКИ АКТИВНЫХ РАСПЛАВОВ С МАТЕРИАЛАМИ КЕРАМИЧЕСКИХ ФОРМ В ВАКУУМЕ

To obtain precise castings from chemically active melts, a special method of precision cas¬ting according to removable models is traditionally used, consisting in the manufacture of ceramic molds on an ethyl silicate binder and further filling with melt in vacuum. At the same time, when forming castings of a responsible purpose by pouring titanium and heat-resistant nickel alloys in a vacuum, the current technology causes a high defect due to the identification of various surface casting defects that are unacceptable when working parts under the action of repeatedly repeated temperature changes and alternating mechanical loads. The analysis showed that the main reason for this defect is the lack of thermochemical resistance of ceramic corundum molds on an ethyl silicate binder to interaction with poured titanium and heat-resistant nickel al-loys in vacuum. The possibility of obtaining high-quality castings from chemically active alloys is reduced to the use as a binder of ceramic forms of materials that are resistant to thermal dissociation in vacuum at heating temperatures of 1913–1973 K. For this purpose, it is proposed to use a silica-free binder – an aqueous solution of aluminum phosphate concentrate. The composition of the mold made according to the proposed technology, in which there is no silica, excluded the harmful effect of oxidation processes in vacuum on the quality of castings from chemically active alloys. Ceramic electrocorundum molds based on aluminum phosphate concentrate are resistant to thermal dissociation and interaction with chemically active metals poured in vacuum. This will reduce defects in non-metallic inclusions and improve the quality of precision castings made of titanium and heat-resistant nickel alloys.

Correction method for the influence of environmental factors on laser-induced breakdown spectroscopy.

Environmental factors include sample temperature, ambient gas composition, and pressure, which have a significant impact on the accuracy and stability of the analysis results of laser-induced breakdown spectroscopy (LIBS). In this study, a method for simultaneously correcting the influence of several environmental factors is proposed. When the calibration and application environment are different, only one sample is needed to be measured in the application environment to correct the influence of environmental factors, so that the calibration model can obtain good analytical accuracy in this environment. When using one to four samples to correct the influence of environmental factors, the application of the calibration models constructed under solid-state conditions at atmosphere pressure to analyze seven elements in molten alloys in vacuum demonstrated the average root mean square error of prediction (RMSEP) of 0.57%, 0.51%, 0.41%, and 0.30% respectively. The accuracy of using only one sample to correct the influence of environmental factors was much higher than using two samples to establish calibration models in the application environment. This proved the effectiveness of the developed method for reducing the difficulty and cost of calibration in the metallurgical processes.

Comparative Study on Tribological Behaviors of Two TiZr-Based Alloys in Vacuum

Comparative Study on Tribological Behaviors of Two TiZr-Based Alloys in Vacuum

Effect of welding time on microstructure and properties of Al2O3/AlSiMg/1A95 aluminum alloy direct brazing joint

Al2O3 ceramic and 1A95 aluminum alloy vacuum brazed joints were prepared with Al-Si-Mg-La solder. The effects of brazing time on the structure and shear properties of brazed joints were studied, and the interface of the joints was analyzed. Studies have shown that the shear strength of Al2O3/Ag-Si-Mg-La/Al joints all show a trend of increasing first and then decreasing with the increase of brazing temperature and holding time; when the best brazing process is 590°C×30 min, the boundary between AlSiMgLa solder and aluminum alloy disappears; the interface between Al2O3 ceramic and solder is well bonded, and the shear strength reaches 65.12 MPa. The fracture form of the joint is brittle fracture. Under different brazing process parameters, the fracture position of the joint is mainly divided into two types: when the joint strength is low, the fracture occurs near the interface between the aluminum alloy and the brazing filler metal layer; when the joint strength is higher, the fracture occurs at the interface between the Al2O3 ceramic and the solder.

Effect of welding temperature on microstructure and properties of Al2O3/AlSiMgLa/1A95 aluminum alloy direct brazing joint

Al2O3 ceramic and 1A95 aluminum alloy vacuum brazed joints were prepared with Al-Si-Mg-La solder. The effects of brazing temperature on the structure and shear properties of brazed joints were studied, and the interface of the joints was analyzed. Studies have shown that the shear strength of Al2O3/Ag-Si-Mg-La/Al joints all show a trend of increasing first and then decreasing with the increase of brazing temperature and holding time; when the best brazing process is 590°C×20 min, the boundary between Al-Si-Mg-La solder and aluminum alloy disappears; the interface between Al2O3 ceramic and solder is well bonded, and the shear strength is 56.74MPa. The fracture form of the joint is brittle fracture. Under different brazing process parameters, the fracture position of the joint is mainly divided into two types: when the joint strength is low, the fracture occurs near the interface between the aluminum alloy and the brazing filler metal layer; when the joint strength is higher, the fracture occurs at the interface between the Al2O3 ceramic and the solder.

Time evolution of copper-aluminum alloy laser-produced plasmas in vacuum

Spectral and transient image measurements of the spatiotemporal evolution of laser-produced plasma of copper-aluminum alloy in vacuum and corresponding radiation hydrodynamics simulations are reported. The visible spectrum and time resolved plasma plume images were obtained for time delays from 10-100 ns at different positions near the target surface using space and time-resolved spectroscopy and time-resolved transient imaging. Using a program developed for multi-element laser-produced plasma simulation based on the radiation hydrodynamics model combined with experimental spectrum, ion/electron densities and plasma temperature as well as their time evolutions were obtained. The temporal and spatial distribution characteristics for Cu and Al ions in the plasma are clarified. These results will be helpful for understanding the dynamics of the different ions during expansion of multi-element laser-produced plasma and its applications.