Molten Condition Research Articles

Effect of full melt temperature sintering and semi-melt heat preservation sintering on microstructure and mechanical properties of Ti3SiC2/Cu composites

The influence of sintering parameters on the microstructure, phase composition and mechanical property of the Ti3SiC2/Cu composites sintered by spark plasma sintering technique was investigated and the related sintering mechanism was clarified in detail. Results indicated that during the heating process, one part of the high energy adsorbed by the composites let Cu melt and fill the gaps inside the composites. Meanwhile, there’s different molten condition about Cu duel to different heating temperature that cause Cu fill in the most space between Ti3SiC2 particles. The other part of the energy caused to the local high temperature, contributing for the chemical reaction and the formation of TiCx and Cu3Si. Therefore, at the same heating rate, the composites showed better mechanical property and higher density with a longer heating time. The heating stage played an important role in the change of the mechanical property, microstructure and volume of the composites. During the holding stage, because the amount of the reactants significantly decreased, the related chemical reaction got slow and the energy needed during this stage was lower than that during the heating stage. And the particle of Ti3SiC2 need more time for moving to the space of Cu. Therefore, the higher the holding temperature, the more significant was the diffusion of the phases. The more uniform the phases, the higher was the density. When heating temperature (higher than holding temperature) cause Cu complete melt and holding temperature keep the Cu in semi-melt, there will be a more effective sintering method.

In situ synthesis of a binary Ti–10at% Nb alloy by electron beam melting using a mixture of elemental niobium and titanium powders

Abstract This study reports the results of the preliminary assessment to fabricate Ti-10at% Nb alloy by electron beam melting (EBM®) from a blend of elemental Nb and Ti powders. The microstructure of the EBM-manufactured Ti-10at% Nb alloys is sensitive to the following factors: different sintering properties of Nb and Ti powders, powder particle properties, material viscosities at varying melt pool temperatures, β-stabilizer element content and the EBM® process parameters. Three phases were observed in as-manufactured Ti-10at% Nb alloy: μm-size Nb phase, a Nb-rich β-solid solution surrounding Nb phase, lamellar structured α-phase and β-solid solution with different distribution and volume fraction. Thus, the combination of powder particle characteristics, very short time material spends in molten condition and sluggish kinetics of mixing and diffusional process in Ti-Nb alloy results in heterogeneous microstructures depending on the local Nb content in the powder blend and the EBM® process conditions.

SEM and EDAX Evaluation of Al-Fe Alloy

The scanning electron microscopy (SEM) and energy dispersive X-Ray analysis of the Al-Fe alloy revealed the formation of varying ironaluminide intermetallic compounds. The Al-Fe alloys were produced by varying the composition of Fe. The pure ‘Al’ billets were heated up to 750оc and in the molten condition of aluminium ‘Fe’ powder was added resulting in an exothermic reaction. The exothermic reaction raised the molten bath temperature to ~ 1400оc which activated the formation of intermetallic compound.

Prediction and analysis of high velocity oxy fuel (HVOF) sprayed coating using artificial neural network

Thermal spray comprises a group of coating processes for coating manufacturing in which metallic or nonmetallic materials are deposited in a molten or semi-molten condition. Most often, the coating properties are significantly influenced by the operating parameters. However, obtaining a comprehensive modeling or analytical analysis of the thermal spray process is too difficult to be practical due to the complex chemical and thermodynamic reactions. Accordingly, the present study aims at applying an artificial neural network (ANN) model to predict the HVOF sprayed Cr3C2−25NiCr coatings and analyze the influence of operating parameters regardless of the intermediate process. The process parameters, which were automatically recorded by the homemade HVOF spray system during the spray process, were served as the inputs for the ANN model. Then, the porosity, microhardness and wear rate of coatings were measured and considered as targets for the ANN model. After configuring and training procedure of the model, the predicted results were compared to the results of experimental data. The good consistency found between these results permits to verify the reliability and accuracy of the trained ANN model. Additionally, the mean impact value (MIV) analysis was conducted to quantitatively explore the relative significance of each input variable for improving the effective prediction.

Antibacterial polymer fibres by rosin compounding and melt-spinning

The antibacterial features of natural pine/spruce rosin are well established, yet the functionality in various thermoplastics has not been surveyed. This work focuses on the processing of industrial grade purified rosin mixed with polyethylene (PE), polypropylene (PP), polylactic acid (PLA), polyamide (PA) and corn starch based biopolymer (CS). Homopolymer masterbatches were extrusion-compounded and melt-spun to form fibres for a wide range of products, such as filters, reinforcements, clothing and medical textiles. Due to the versatile chemical structure of rosin, it was observed compatible with all the selected polymers. In general, the rosin-blended systems were shear-thinning in a molten condition. The doped fibres spun of PE and PP indicated adequate melt-spinning capability and proper mechanical properties in terms of ultimate strength and Young's modulus. The antibacterial response was found dependent on the selected polymer. Especially PE with a 10 wt% rosin content showed significant antibacterial effects against Escherichia coli DH5α and Staphylococcus aureus ATCC 12598 when analysed in the Ringer's solution for 24 h.

Deep drawing of organic sheets made of hybrid recycled carbon and thermoplastic polyamide 6 staple fiber yarns

Fully impregnated fiber-reinforced thermoplastic sheets, or the so-called organic sheets, allow the thermoforming of parts within very short cycle times. This article describes the development of the next generation of organic sheet materials based on recycled carbon fibers and polyamide 6 staple fiber yarns. Regardless of the recycled nature of the fibers and an average fiber length of 25 mm, the organic sheets still reach a comparable level of the tensile strength and modulus of continuous fiber-reinforced organic sheets made of virgin CF with the same reinforcement structure. Due to the staple fiber yarn architecture, the organic sheets feature a deep-drawing ability of a total plastic deformation up to 50% in the fiber direction. The effect is enabled via an interfiber sliding when the organic sheet is processed in the molten condition. The creation of a finite element model for the thermoforming process simulation of the material is also presented. Predictions of the plastic strain distribution and its magnitude are shown to agree well with forming experiments where a curved geometry is formed to different depths.

Analysis of Economic and Energy Efficiency of Using Electric-Arc Reduction for Iron-Containing Materials

For many years an important task for metallurgical scientists is the search for alternative technologies of iron production from mineral raw materials without using expensive coke, natural gas and with the least pressure on ecology. Technologies are required with maximum extraction of iron from ore, and with the least pollution of the atmosphere using cheap and least scarce reducing agents, for example power generating coal. Recently in OAO VNIIMT a new method has been developed and proven under laboratory conditions for direct preparation of iron by reduction of fine-grained material with solid reducing agent in a direct current electric arc furnace, including ground ore, iron-bearing sludge, etc. This technology makes it possible to prepare cast iron containing 3–4% carbon in a molten condition that may be granulated, cast into pigs, and treated in a ladle-furnace unit with minimum specific yield of gas and slag.

The influence of vermiculite on the ash deposition formation process of Zhundong coal

Zhundong coal, rich in the Alkali and Alkaline Earth Metal elements, causes severe ash deposition during the combustion in many power plants. In this paper, the influence of vermiculite, as an additive, on ash deposition formation and the corrosion phenomenon caused by ash deposition are investigated in a drop tube furnace system. The formation process of ash deposition under real working condition can be simulated in this furnace system. The results show that vermiculite has a significant inhibition effect on the formation and growing process of ash deposition, as well as the corrosion phenomenon. At the beginning of ash deposition, the swelling vermiculite can effectively absorb the SO2 in the flue gas, which restrains the formation of Na2SO4 in the inner ash, close to the surface of heat exchangers. The mineral in internal inner ash gets changed and the phenomenon of corrosion on the heat exchangers surface gets alleviated. Meanwhile, the external inner ash presents with loose structure instead of the molten condition, which lowers possibility for ash deposition to grow. In outer ash deposition, close to the flue gas, the content of layered particles with high melting point, as Mg2SiO4, increases and viscous particles, like Ca2Al2SiO7, are separated from each other by the force of the vermiculite swelling. As a result, adding vermiculite makes it hard for ash deposition to form and grow. According to the experiments, with more than 5% blending ratio of vermiculite, the vermiculite additive has a positive effect on restricting the ash deposition.

Effect of PANI on Thermal, Mechanical and Electromagnetic Properties of HDPE/LLDPE/PANI Composites

In this work, polyaniline (PANI) in emeraldine-base form, synthesized by chemical oxidation polymerization, was protonated with hydrochloric acid (HCl). Composites based on high-density polyethylene (HDPE) and linear-low density polyethylene (LLDPE) blends with PANI were prepared in molten condition using a torque rheometer. The effect of compatibilizer agent (maleic anhydride-grafted high density polyethylene, HDPE-g-MA) and different contents of PANI on the blends-based composites was also investigated. Thermal, mechanical, and electromagnetic (electric permittivity) measurements and morphological aspects of the composites were evaluated. The addition of PANI content in the composites decreases the degree of crystallinity of HDPE and LLDPE blends, which implies that PANI particles make it difficult for co-crystallization to occur in the HDPE and LLDPE, respectively. On the other hand, the addition of compatibilizer agent in the HDPE and LLDPE blends increased the degree of crystallinity. The complex parameters of permittivity in the frequency range of 8.2 to 12.4 GHz varied as a function of the PANI content in the blend. It was also observed that the compatibilizer agent increased the composite stiffness and decreased the electric permittivity values. This result shows that the increasing rigidity of the molecular structure of the polyethylene matrix hindered the dissipation of the electromagnetic energy in the sample.

Experimental study on twin-roll strip casting of Cu-9Ni-6Sn alloy

A strip billet of Cu-9Ni-6Sn alloy was prepared by vacuum melting and twin-roll casting while another billet with the same chemical composition was prepared by vacuum melting and general casting. Component distribution and microstructure of the two kinds of copper alloy from different processing procedures were analysed by metallographic examination and SEM. The results showed that there were massive dendritic crystals with obvious segregation of tin in the sample prepared by general casting. The sample processed by twin-roll casting process had more fine grains with homogenous distributed tin compared to that prepared by general casting. The results demonstrated that the fine grains with homogenous distributed tin were caused by the excellent cooling ability of twin-roll casting. The extremely fast cooling speed retained the homogenous component distribution in molten condition and there was no time for grains to grow up. The experiment indicated twin-roll casting was a feasible process to produce Cu-9Ni-6Sn alloy.

(IJCESEN)

In thermal spraying process, a commercial powder is heated and accelerated simultaneously using a heat source and deposited in a molten or semi-molten condition on a prepared substrate. Coating quality highly depends on some important surface parameters such as the thermo-chemical and physical properties of both powder and substrate, the surface state, the preheated temperature, and the existence of oxidation. In pratice, it is commonly accepted that pre-heating the substrate, prior a thermal spray operation, have a great benefits to increase adhesion. However, this method is not routinely used. In this work, the preheating effect of XC18 steel substrates on the flattening behavior of two commercially available flame-sprayed powders was investigated in a temperature range from ambiant to 500 °C. The conventional flame spray gun was used to accelerate molten particles and Infra-red pyrometer was used to monitor the substrate temperature during a preheating process. Tthe coatings cross section microstructure and elements distribution was performed using SEM with EDS and optical microscope.

Researches Structure and Properties of Self-Fluxing Coating, Obtained by Air-Plasma Spraying

The structural features of self-fluxing coatings obtained by air-plasma spraying with a unit of annular injection of powder are discussed in the article. It is shown that the application of an annular injection unit makes it possible to increase significantly the efficiency of particle heating in contrast to the point injection of a powder into the plasma jet. It is shown by optical and scanning electron microscopy that the major part of particles which form the coating is in a molten or plasticized condition in the plasma jet. It is revealed by transmission electron microscopy that a high cooling rate of these particles contributes to the formation of the γ-submicrocrystalline supersaturated Ni-based solid solution with an average grain size of 80 nm. To provide high technological and tribological properties it is necessary to carry out plasma spraying at an arc current less than 170 A.

Air plasma sprayed coatings of self-fluxing powder materials

The article discusses the structural features of self-fluxing coatings obtained by plasma spraying air from entering the hub ring and the gas-dynamic focusing powder. It was shown that, unlike the unilateral spot powder inlet into the plasma jet, the use of the annular input node allows to increase heating efficiency and to accelerate the particles in the plasma stream. By optical and scanning electron microscopy that most of the particles forming the coating, in the plasma jet is in a molten or plasticized condition. Transmission electron microscopy revealed that high cooling rates of such particles contribute to the formation of γ-SMC supersaturated solid solution Ni-based average grain size of 80 nm.

Development of a Multi-Step Synthesis and Workup Sequence for an Integrated, Continuous Manufacturing Process of a Pharmaceutical

The development and operation of the synthesis and workup steps of a fully integrated, continuous manufacturing plant for synthesizing aliskiren, a small molecule pharmaceutical, are presented. The plant started with advanced intermediates, two synthetic steps away from the final active pharmaceutical ingredient, and ended with finished tablets. The entire process was run on several occasions, with the data presented herein corresponding to a 240 h run at a nominal throughput of 41 g h–1 of aliskiren. The first reaction was performed solvent-free in a molten condition at a high temperature, achieving high yields (90%) and avoiding solid handling and a long residence time (due to higher concentrations compared to dilute conditions when run at lower temperatures in a solvent). The resulting stream was worked-up inline using liquid–liquid extraction with membrane-based separators that were scaled-up from microfluidic designs. The second reaction involved a Boc deprotection, using aqueous HCl that was rapidly...

Modelling the dynamics of the tilt-casting process and the effect of the mould design on the casting quality

All titanium alloys are highly reactive in the molten condition and so are usually melted in a water-cooled copper crucible to avoid contamination using processes such as Induction Skull Melting (ISM). These provide only limited superheat which, coupled with the surface turbulence inherent in most conventional mould filling processes, results in entrainment defects such as bubbles in the castings. To overcome these problems, a novel tilt-casting process has been developed in which the mould is attached directly to the ISM crucible holding the melt and the two are then rotated together to achieve a tranquil transfer of the metal into the mould. From the modelling point of view, this process involves complex three-phase flow, heat transfer and solidification. In this paper, the development of a numerical model of the tilt-casting process is presented featuring several novel algorithm developments introduced into a general CFD package (PHYSICA) to model the complex dynamic interaction of the liquid metal and melting atmosphere. These developments relate to the front tracking and heat transfer representations and to a casting-specific adaptation of the turbulence model to account for an advancing solid front. Calculations have been performed for a 0.4 m long turbine blade cast in a titanium aluminide alloy using different mould designs. It is shown that the feeder/basin configuration has a crucial influence on the casting quality. The computational results are validated against actual castings and are used to support an experimental programme. Although fluid flow and heat transfer are inseparable in a casting, the emphasis in this paper will be on the fluid dynamics of mould filling and its influence on cast quality rather than heat transfer and solidification which has been reported elsewhere.

Effect of controlled electron beam irradiation on the rheological properties of nanosilica‐filled LDPE‐EVA based thermoplastic elastomer

AbstractThe effect of controlled electron beam irradiation on the rheological properties of a model LDPE‐EVA thermoplastic elastomer (TPE) system filled with silica nanoparticles is explored in this article. The pristine silica particles were mixed with LDPE‐EVA system in molten condition by varying the sequence of addition and amount of nanosilica. In one composition, Si69 was used to improve the state of dispersion of nanosilica. The rheological behavior of irradiated TPE systems is influenced remarkably by irradiation dose, loadings of silica, variation of sequence, and addition of Si69. All filled TPE systems register an increase in elastic response with increasing frequency and with increase in irradiation dose. Upon irradiation, melt viscosity increases when compared with the unirradiated samples because of the crosslinking effect and improvements in interfacial bonding. The viscoelastic response varies markedly with the temperature. The radiation sensitizing effect of silica is reflected from the rheological data. The dynamic and steady shear rheological properties do not follow a simple correlation. Finally, the rheological behavior is correlated with the morphology of the irradiated systems processed at various shear rates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The effect of Ca on the in vitro corrosion performance of biodegradable Mg–Nd–Y–Zr alloy

The effect of 0.4% Ca on the in vitro corrosion behavior of Mg–1.2% Nd–0.5% Y–0.5% Zr was evaluated in a simulated physiological environment in the form of 0.9% NaCl solution saturated with Mg(OH)2 at ambient temperature and at 37 °C. The microstructure examination was carried out using optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analysis. The corrosion behavior was evaluated by immersion test, salt spray testing, and potentiodynamic polarization analysis. The stress corrosion behavior was examined using slow strain rate testing analysis in different strain rates. The results obtained have shown that the addition of 0.4% Ca has a beneficial effect on the corrosion resistance of the tested alloy. This was mainly attributed to the effect of calcium, which reduces oxidation in the molten condition and consequently improves the soundness of the obtained casting. Hence, it is believed that the reduction in the extent of inherent casting defects in the alloy containing calcium overcomes the detrimental micro-galvanic effect of the Mg2Ca phase that was formed in the tested alloy. Contrary to the beneficial effect of calcium on the corrosion performance, the addition of calcium has a damaging effect on the stress corrosion behavior in terms of reduced ultimate tensile strength and ductility. This was mainly due to the embrittlement effect of calcium that was generated by the formation and distribution of Mg2Ca phase at grain boundaries.

Structure and Property Studies on Austempered and As-Cast Ausferritic Gray Cast Irons

A high-strength and wear-resistant alloyed gray iron with ausferritic microstructure on solidification directly from molten condition could be made in a Ni and Mo alloyed gray cast iron. The as-cast ausferritic cast iron was compared with two conventionally austempered gray iron with and without Ni and Mo additions. The various phase constitution and volume fractions were analyzed using optical, SEM and XRD analyses. The various aspects of the alloy chemistry and processing conditions have been correlated with the microstructure and mechanical properties obtained. The analysis showed that the Ni-Mo alloyed austempered gray iron and the directly as-cast austempered gray iron had similar phase constitutions. The strength of the direct as-cast alloy with ausferritic microstructure was higher than the others due to its higher austenite content and carbide distribution. The wear rate of the conventionally austempered Ni and Mo containing alloy and direct as-cast ausferritic alloys is 20% of the austempered gray iron without Ni and Mo with friction coefficient less than 0.4.

Experimental study on copper cathode erosion rate and rotational velocity of magnetically driven arcs in a well-type cathode non-transferred plasma torch operating in air

The cathode erosion rate, arc root velocity and output power of a well-type cathode (WTC), non-transferred plasma torch operating in air are studied experimentally in this paper. An external solenoid to generate a magnetically driven arc and a circular swirler to produce a vortex flow structure are equipped in the studied torch system, which is designed to reduce the erosion rate at the cathode. A least square technique is applied to correlate the system parameters, i.e. current, axial magnetic field and mass flow rate, with the cathode erosion rate, arc root velocity and system power output. In the studied WTC torch system, the cathode erosion has a major thermal erosion component and a minor component due to the ion-bombardment effect. The cathode erosion increases with the increase of current due to the enhancement in both Joule heating and ion bombardment. The axial magnetic field can significantly reduce the cathode erosion by reducing the thermal loading of cathode materials at the arc root and improving the heat transfer to gas near the cathode. But, the rise in the mass flow rate leads to the deterioration of erosion, since the ion-bombardment effect prevails over the convective cooling at the cathode. The most dominant system parameter to influence the arc root velocity is the axial magnetic field, which is mainly contributed to the magnetic force driving the arc. The growth in current has a negative impact on increasing the arc root velocity, because the friction force acting at the spot due to a severe molten condition becomes the dominant component counteracting the magnetic force. The mass flow rate also suppresses the arc root velocity, as a result of which the arc root moves in the direction against that of the swirled working gas. All system parameters such as current, magnetic field and gas flow rate increase with the increase in the torch output power. The experimental evidences suggest that the axial magnetic field is the most important parameter to operate the straight-polarity WTC plasma torch at high output power with a limited cathode erosion rate. This emphasizes the importance of an external magnetic field on a WTC torch system for reducing the erosion at the cathode.

Retardation of spalling by the addition of Ag in Sn–Zn–Bi solder with the Au/Ni metallization

The work presented in this paper focuses on the role of Ag addition in the Sn–8%Zn–3%Bi solder on the shear strengths and the interfacial reactions with Au/Ni/Cu pad metallization in ball grid array (BGA) applications. Sn–Zn–Bi(–Ag) solder alloys were kept in molten condition (240 °C) on the Au/electrolytic Ni/Cu bond pads for different time periods ranging from 1 to 60 min. After the shear test, fracture surfaces were investigated by scanning electron microscopy. Cross-sectional studies of the interfaces were also conducted to correlate with the fracture surfaces. The results indicated that the spalling of the Au–Zn intermetallic compound (IMC) layer was regulated by the addition of 0.3%Ag in Sn–Zn–Bi solder. The retardation of spalling of the initial IMC, limited the formation of Ni–Zn compound in the Ag doped Sn–Zn–Bi solder. The formation of thick Ni–Zn IMC layer in Sn–Zn–Bi alloy deteriorated the mechanical strength of the joints after extended reflow.