Low-melting Metals Research Articles

Effect of Bismuth and Lead on the Phase Composition and Structure of the Al–5% Si–4% Cu–4% Sn Alloy

This article is devoted to the topical problem of developing antifriction aluminum alloys economically alloyed with low-melting metals. It was found in earlier experiments that an alloy containing about 5% Si, 4% Cu, and 6% Sn (wt %) has a balanced complex of manufacturing and physicomechanical properties. The possibility of decreasing the tin concentration to 4% and its partial substitution by other low-melting metals such as bismuth and lead is considered because of the high cost of tin. The joint and separate influence of these elements on the phase composition of the Al–5% Si–4% Cu–4% Sn alloy is studied using thermodynamic calculations (in the Thermo-Calc program), including the construction of polythermal and isothermal sections. It is shown that additives of lead and bismuth cause the appearance of an extensive area of fluid stratification, so their total concentration should not exceed 1–2%. The phase composition and microstructure of the Al–5% Si–4% Cu–4% Sn–0.5% Pb–0.5% Bi alloy are studied using scanning electron microscopy and X-ray spectral microanalysis. It is revealed that low-melting metals are uniformly distributed in the structure of the alloy in the cast state and, in totality of properties, this material surpasses BrO4Ts4S17 antifriction bronze. Heat treatment according to the T6 mode leads to a significant increase in the hardness of the alloy under study. However, local fusion of the low-melting component occurs during heating for quenching at 500°C, which causes the deterioration of the microstructure during recrystallization and, consequently, causes alloy embrittlement.

Effect of bismuth and lead on phase composition and structure of Al—5%Si—4%Cu—4%Sn alloy

The article focuses on the actual problem of creating economically alloyed antifriction aluminum alloys doped with low-melting metals. It was found in earlier experiments that an alloy containing about 5 % Si, 4% Cu and 6 % Sn (wt.%) has a balanced complex of technological and physicomechanical properties. Due to the high cost of tin, this paper considers the possibility of reducing its concentration to 4 %, and its partial replacement by other low-melting metals, such as bismuth and lead. Thermodynamic calculations (in the Thermo-Calc program) including the construction of polythermal and isothermal sections are used to study the joint and separate influence ofthese elements on the phase composition of the Al—5%Si—4%Cu—4%Sn alloy. It is shown that the addition of lead and bismuth leads to the appearance of an extensive area of fluid separation, and therefore their total concentration should not exceed 1—2 %. The phase composition and microstructure ofthe Al—5%Si—4%Cu—4%Sn—0,5%Pb—0,5%Bi alloy were studied using scanning electron microscopy and micro X-ray spectral analysis. It was found that in the cast state, low-melting metals are evenly distributed in the structure of the alloy, and in terms of the combination of properties, the experimental aluminum alloys surpass the BrO4Z4S17 antifriction bronze. Heat treatment mode T6 leads to a significant increase in the hardness of the experimental alloy. However, in the process of heating for quenching at 500 °C, local fusion of the low-melting component occurs, which leads to deterioration of the microstructure upon re-crystallization and, as a result, causes alloy embrittlement.

Brazing Characteristics and Bonding Strength of Pure Titanium Joints Brazed with Low-Melting Temperature Zi-17Ti-22Ni Filler Metal.

The brazing characteristics and bonding strengths of pure titanium joints are evaluated for joints brazed with Zr-17Ti-22Ni filler. Vacuum brazing was conducted at temperatures between the melting temperatures of the filler metals and the beta-transition temperature of pure titanium at 3 MPa of pressure for 5 min. Fracturing of the pure titanium joint brazed at 1,093 K occurred before yielding during the tensile tests owing to the presence of a serious segregation region containing harder and more brittle [Ti, Zr]2Ni intermetallic compounds. In contrast, in pure titanium joints brazed at and above 1,113 K, fracturing occurred at the base metal. The yield strengths of the samples brazed at 1,113 K-1,133 K were estimated to be in the range of 320-350 MPa and the ultimate tensile strengths likewise ranged from 350 to 380 MPa. The strength of pure titanium brazed at 1,153 K decreased rapidly. The results of this study show that the optimum temperature to ensure good performance after the brazing of pure titanium with Zr-17Ti-22Ni as a filler metal ranges from 1,113 K to 1,133 K.

Activity of Lanthanum in Zn-Containing Alloys: La–Zn, La–U–Zn, and La–U–Ga–Zn Systems

The effect of alloy components on the thermodynamic properties of f elements is studied on Zn‑containing alloys. The activity of lanthanum in the La–Zn, La–U–Zn, and La–U–Ga–Zn systems and the activity of uranium in the U–Zn system in the range 573–1073 K are determined. The effect of a second low-melting metal (gallium) and a second f element (uranium) on the activity of lanthanum in zinc-containing alloys is analyzed.

Effect of Ni on mechanical behavior of Al2O3/(W,Ti)C ceramic tool materials at ambient and elevated temperatures

Two types of Al2O3/(W0.5,Ti0.5)C ceramic composites with and without metal phase Ni were studied in this research. The evolution mechanism of bending strength and fracture toughness at both ambient and high temperature(600 ∼ 1000 °C) was studied. The influence of nickel on mechanical behavior and microstructure of composites was also analyzed in the test temperature range. The results showed that the bending strength of both ceramic composites decreased with gradually increased temperature. The bending strength of Al2O3/(W0.5,Ti0.5)C/Ni was greater than that of Al2O3/(W0.5,Ti0.5)C ceramic composites at room temperature. However, the bending strength of Al2O3/(W0.5,Ti0.5)C/Ni decreased more rapidly at high temperature. The fracture toughness of Al2O3/(W0.5,Ti0.5)C/Ni was always greater than that of Al2O3/(W0.5,Ti0.5)C at different temperatures. The addition of metal phase had a positive impact on the fracture toughness at different temperatures. It was found that the matrix and the toughening phase were well combined by the metal phase, so the room temperature bending strength of Al2O3/(W0.5,Ti0.5)C/Ni was enhanced. However, the decrease of interfacial bonding strength caused by the low-melting metal phase led to the fracture mode changed. Moreover, the elastic modulus of Al2O3/(W0.5,Ti0.5)C/Ni decreased faster at elevated temperatures, which resulted in lower bending strength. The research on the evolution law of mechanical behavior of composites at elevated temperatures has important guiding significance for the design of materials and the choice of cutting parameters.

Comparative Analysis of the Ternary Al–Si–X and Al–Cu–X (X = Sn, Pb, Bi, Cd, In) Systems in the Aluminum Alloy Range

Thermodynamic calculations are used to study the phase compositions of Al–Si–X and Al–Cu–X alloys, where X is a low-melting metal (Sn, Pb, Bi, Cd, In). Poly- and isothermal sections are used to determine the temperatures of invariant monotectic reactions. The formation of globular low-melting phase inclusions in heating at 500°C is found by experimental techniques.

Separation of Low-Melting Metal Melts in a Thin Inclined Capillary

Direct numerical simulation of the process of separation of binary low-melting metal melts in a thin nonuniformly heated inclined capillary is carried out. A physical model which describes the macroscopic motion in the melt and the process of separation of the liquid mixture in components is constructed on the basis of laws and equations valid for the multiphase hydrodynamic systems. The calculation results are compared with the experimental data. The separation time is compared for various angles of inclination of the layer, the characteristic concentration fork which demonstrates separation dynamics is reproduced, and the qualitative agreement with the experiment is obtained for the component concentrations in the cross-section. In the course of numerical simulation, that replicates the succession of experimental actions with the maximum precision, the presence of the specific maximum for the difference between the end-face concentrations at a certain angle of inclination of the channel is confirmed. The radical difference between the calculation results obtained within the framework of the model considered and the conclusions made earlier in explanation of the experiment by other authors is demonstrated.

Влияние диффузионного титанирования из среды легкоплавких жидкометаллических растворов на работоспособность режущего твердосплавного инструмента типа ТК и ВК

Влияние диффузионного титанирования из среды легкоплавких жидкометаллических растворов на работоспособность режущего твердосплавного инструмента типа ТК и ВК

Three-Dimensional Flow Studies in Cylindrical Magnetohydrodynamic Experiments Using Ultrasound Array Velocimetry.

Crystal growth processes can profit from an electromagnetically driven melt flow since controlling them allows optimizing the mass and heat transfers in the melt and, thereby, improves the structural and electrical properties of the grown crystals. This process optimization requires a precise understanding of magnetohydrodynamics (MHD) phenomena in crystal growth. Studying time-dependent MHD demands for a high temporal resolution combined with a long measurement duration to analyze the transitional flow behavior. Furthermore, a spatially resolved measurement of the global flow structure is desired to capture the complex 3-D flow structures. We present an ultrasound array Doppler velocimeter (UADV) for time-resolved flow imaging in MHD model experiments with low-melting metals. Flow imaging at frame rates of several Hertz is achieved by using a combined spatial and temporal multiplexing scheme. Long-running measurements are enabled by a field-programmable gate array (FPGA)-based signal processing that reduces the measurement data rate by a factor of 5. A reconstruction of the 3-D flow structure in cylindrical containers with a rotation-symmetric flow is proposed. The UADV is demonstrated at an MHD experiment with a melt flow in a cylindrical container driven by a traveling magnetic field. The transition from a laminar to a time-dependent flow is studied, revealing an oscillating flow. The demonstration of the 3-D reconstruction gives comprehensive insight into the global flow structure. Hence, the UADV method is shown to be a valuable tool for measuring complex, time-dependent melt flows, which can contribute to a better understanding of the flow phenomena during crystal growth.

Artificial aging of hard-alloy cutting tool with titanium diffusion coating as a way to increase its persistence

The paper describes the technology of applying titanium diffusion coating to the cutting tool from low-melting liquid metal solutions. The results of thermal treatment of the carbide cutting blades (WC and TiC type) after titanium diffusion coating from low-melting liquid metal solutions are given. The results of thermal treatment influence on the firmness of cutting tool having titanium coating are shown. It is found out that thermal treatment temperature, its duration and material composition influence affect tool durability and coating micro-hardness. It is revealed that thermal treatment of the carbide instrument with titanium diffusion coating lets to increase its persistence by 1.79 times comparing to the tool without coating. But without thermal treatment persistence of the instrument with coating increases by 9 times in comparison to the tool without coating.

Method for calculating the thermal diffusivity and thermal conductivity of heavy low-melting metals in the liquid state

An approach is presented that allows predicting the transport properties of metallic melts without involving data on the electrical conductivity. To determine the thermal diffusivity, only information from the Mendeleev table is required. It is sufficient to know the molar mass and the number of valence electrons. To determine the thermal conductivity, additional information is required on the density and heat capacity of the metal.

Macrokinetics of combustion of layered compositions with a low-melting inert layer

The paper represents a mathematical model for the gasless combustion of a layered composition. The inner layer of the composition consists of an inert low-melting metal. Other layers consist of a highly exothermic gasless mixture. Metal of the inner layer melts during the combustion of adjacent layers. The melt under the influence of surface tension forces spreads in porous combustion products of the gasless mixture to form a composite material. The capillary flow of melt in porous channels is limited by the temperature of the carcass equal to the melting point. The results have shown that the time required for a combustion wave to propagate through an inert layer depends on its thickness and thermal conductivity. The modes of combustion synthesis are determined for layered composite materials. The dynamics of the structure formation of composite materials is considered depending on the thickness of the inner metal layer and the coefficient of external heat exchange.

Mechanisms Governing Fine Fragmentation of Hot Melt Immersed in Cold Water

Hypotheses about the mechanisms governing fragmentation of superheated liquid metal droplets falling into cold water are analyzed. It is shown that a physical model based on the cavitation–acoustic mechanism governing fine fragmentation of melt under steam explosion conditions is likely the most suitable one for consistently describing the fragmentation of both low-melting and refractory metals. For checking this conjecture, special experiments for studying the processes triggered when cold (20°С) water comes into contact with a heated surface and for measuring the pressure impulses (arising both in coolant and in the hot body) accompanying the coolant flashing were carried out using liquid metal (tin and steel) droplets and superheated solid steel bodies. The working substance temperatures were varied in the range from 200 to 1600°С. The results obtained from the performed experiments are not in contradiction with the melt fine fragmentation process represented by the cavitation–acoustic model. It is shown that the acoustic waves generated during explosive growth of bubbles on a hot surface propagate in the solid body and are alternating in nature. Their intensity (including that at negative pressure values) differs only slightly in the modulus from the pressure impulses measured in the coolant and is sufficient for finely fragmenting the droplets. It is experimentally found—with the use of a conductance measuring technique—that the transition from the coolant film to bubble boiling mode is preceded by a short-term (lasting a few milliseconds) process involving intense interaction of waves at the steam–liquid boundary with the heated surface. The signal from the conductance measuring transducer was subjected to a wavelet analysis for different values of the heated surface temperature. The study results testify that high-frequency (several tens of kilohertz) pulsations of electric current are generated in the preburnout region with their characteristics varying (toward increasing the amplitude and intensity) with time as the heating and heated media come closer into contact with each other. A probabilistic process development scenario is suggested.

Press fit/pressure-soldered joint—improve your press fit

The shortage of resources takes their toll in product development. This means for the drive engineering that the power density has to increase and the manufacturing costs have to decrease. So, the parts and assemblies have to become smaller, while the performance should rise. Following this trend, the joining technologies cannot stand still. At the drive engineering, the elementary press fit (PF) for shaft-hub joints (SHJ) is well known. Its manufacturing is easy and cheap. As a disadvantage, the joint strength is limited due to the coefficient of friction and the maximum possible allowance for interference. Through the combination of an elementary PF with local firmly bonded pressure-soldered joints (PSJ), it is possible to increase the joint strength up to three times of elementary PF by keeping his advantages. For the so-called press fit/pressure-soldered joint (PF/PSJ), it is essential to coat one or both joint areas with a low-melting metal (solder). The main connection is the press fit based on a joint pressure at the joint area. This pressure can be used to generate PSJs (secondary connection). On one hand, the joining area is activated by cracking the oxide layers and on the other hand the inner and outer parts being approached at the distance of influence of atomic forces. The attributes of PF/PSJ are explained with the development of local PSJ at the micro contacts. If the connection will be overloaded (mechanical training), the relative movement causes deformations at the roughness peaks and effects frictional heat. This enhances the size and number of PSJs and increases the joint strength significantly. Another way to increase the transmittable torque is thermal training. With increasing temperature and time, while heating up the shaft-hub joint, the total area of PSJs grows up and a higher torque can be transmitted. The value of contact pressure is just as crucial for the development of PSJs as the temperature, the joining procedure, and the training process.

(Invited) Low Pressure and Atmospheric Pressure Plasma Interactions with Molten Metals and Liquid Droplets for Materials Processing

Several grand challenges in energy storage and conversion need the discovery functional materials that many agree will be composed of complex compositions and nanoscale materials such as nanowires. In this regard, plasma based materials processing has been shown to be promising for combinatorial techniques and scalable processing. For example, our group has shown that gentle plasma excitation of gas phase will allow the use of non-catalytic, low melting metals for catalyzing nanowire growth. Furthermore, the use of plasma oxidation of liquid precursors allows for creation of metastable complex oxide particles with compositional control. A number of examples will be discussed in which the above two techniques are currently being used for accelerating the development of a variety of catalysts including electrocatalysts and materials for storage applications. This talk will highlight our efforts to understand the role of plasmas under two categories: (a) the synergistic effects hydrogen and nitrogen plasma interactions with molten metals; and (b) the oxygen plasma-liquid droplet interactions. To gain insights into these mechanisms we have studied the interaction of hydrogen and nitrogen plasmas with low melting point metals, primarily with gallium. Absorption/desorption experiments as well as theoretical-computational calculations were performed. Experiments have shown an increment of adsorbed gaseous species into the molten metal in the presence of plasmas; furthermore, Density Functional Theory (DFT) calculations suggest a strong interaction between atomic hydrogen and molten gallium that is described as a high absorption on the surface, rapid diffusion and a steady state concentration of the gas inside the bulk. In the case of oxygen plasma-liquid droplet interactions for creating complex oxides, the role of solvated electrons and oxygen radicals will be discussed. Acknowledgements Author acknowledge primary funding support from NSF Solar Project (DMS 1125909), NSF EPSCoR (1355438). Acknowledge with Dr. Miran Mozetic and Dr. Uros Cvelbar for helpful technical discussions regarding measurements. The presentation includes contributions from Dr. Maria Carreon who is currently at U. of Tulsa.

Peculiarities of Mixture Formation and Ignition of the Fuel Mixture in the Metal Sprayer Chamber

The paper presents a device for spraying the low-melting metal coating, based on the rocket chamber operation principle. The design of the fuel nozzle, pre-mixing chamber, and radial combustion chamber is considered. The processes of electro-spark ignition of the fuel mixture and the flame front stabilization are described. The choice of the critical section area as a place of the coating material feeding in the high-temperature combustion products flow is substantiated.

Arcing failure analysis of miniature circuit breaker using nano-W–Cu material

In order to solve the problem of frequent failures of miniature circuit breakers and the resulting short arcing, research on nano-tungsten–copper (nano-W–Cu) material in arcing failure analysis of miniature circuit breakers was carried out by the authors. Ordinary pure copper material, which is widely used in electrical power distribution, exhibits major limitations such as low melting point and metal vapor, which causes frequent failure of the miniature circuit breaker. In this way, on the basis of analyzing the mechanism of miniature circuit breaker arcing and using nano-tungsten–copper material, this paper makes provisions for the 10 kA tolerance test process and conditions of short-circuit current and extracts the commonly used test for a certain type of miniature circuit breaker combined with nano-tungsten–copper material. The test results show that miniature circuit breaker arcing can be reduced by using nano-tungsten–copper material to replace the ordinary pure copper alloy. This could significantly enhance the performance of miniature breaker arcing and its breaking capacity and reduce the miniature circuit breaker arc time as well as the breaking time, which could effectively improve the reliability, security and stability of miniature circuit breakers and effectively solve the problem of miniature circuit breaker arcing failure.

Electrocrystallization and Properties of Supersaturated Solid Solutions of Copper

The role of the alloying element in the formation of the structure and properties of electrolytic copper alloys has been determined. The X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) have shown that electrochemical alloying of copper with low-melting metals leads to the formation of supersaturated solid solutions (SSS) on the cathode, crushing of the crystal structure, smoothing of the surface relief, hardening of the deposits obtained, increasing their solderability and corrosive resistance to acidic media.

Forming characteristics of thin-walled samples by metal fused-coating additive manufacturing

A novel additive manufacturing technology using metal fused-coating additive manufacturing (MFCAM) was developed to fabricate metal samples. The effects of layer thickness on the final shape are discussed in the experiment. Under the same deposition rate, the height of the deposited specimen increases with increasing thickness, and the width of the deposited specimen decreases with the increase of the thickness. The purpose of this work is to provide qualitative and quantitative parameter information during metal forming deposition. Experimental results show that when the layer thickness was set within a reasonable range, the MFCAM process can fabricate low-melting metal parts with high material efficiency (more than 90%). Based on the above research, three-dimensional parts were fabricated to further verify the material efficiency.

Effect of Low-Melting Metals (Pb, Bi, Cd, In) on the Structure, Phase Composition, and Properties of Casting Al–5% Si–4% Cu Alloy

The effect of low-melting metals (Pb, Bi, Cd, In) on the structure, phase composition, and properties of the Al–5% Si–4% Cu alloy was studied using calculations. Polythermal sections have been reported, which show that the considered systems are characterized by the presence of liquid regions and monotectic reactions. The effect of low-melting metals on the microstructure and hardening of base alloy in the cast and heat-treated states has been studied.