Melting Metallurgy Research Articles

Manufacturing and characterization of magnesium alloy foils for use as anode materials in rechargeable magnesium ion batteries

The fabrication of thin foils of magnesium for use as anode material in rechargeable magnesium ion batteries is described. In order to improve its workability, the magnesium was alloyed by melting metallurgy with zinc and/or gadolinium, producing saturated solid solutions. The material was extruded to thin foils and rolled to a thickness of approximately 100 μm. The electrochemical behavior of Mg-1.63 wt% Zn, Mg-1.55 wt% Gd and Mg-1.02 wt% Zn-1.01 wt% Gd was studied in (PhMgCl)2-AlCl3/THF electrolyte by cyclic voltammetry and galvanostatic cycling in symmetrical cells. Analysis of the current-potential curves in the Tafel region and the linear region close to the equilibrium potential show almost no effect of the alloying elements on the exchange current densities (5–45 μA/cm2) and the transfer coefficients. Chemical analyses of the alloy surfaces and the electrolyte demonstrate that the alloying elements not only dissolve with the magnesium during the anodic half-cycles, but also re-deposit during the cathodic half-cycles together with the magnesium and aluminum from the electrolyte. Given the negligible corrosion rate in aprotic electrolytes under such conditions, no adverse effects of alloying elements are expected for the performance of magnesium anodes in secondary batteries.

Alloying by Magnesium: A Route How to Eliminate the Amount of Ti2Ni Phase in Ni-Ti Alloy

This article offers completely new results in the research of NiTi alloys produced by Self-propagating High-temperature Synthesis (SHS). There is investigated the effect of addition of magnesium on the microstructure, phase composition and especially, the amount of undesirable Ti2Ni phase. This phase is unwanted in NiTi alloy because of its brittleness. Moreover, this one is stabilized by oxygen and forms during SHS process. Selected preparation method is considered as an alternative to the melting metallurgy, which produced products with poor homogeneity and purity. For this reason, SHS process has been studied intensely and many researchers have tried to eliminate secondary phases unsuccessfully. Our research showed that alloying by element with high affinity to oxygen causes disappearance of Ti2Ni phase.

Compressive, tensile and wear behavior of ex situ Al/AlN metal matrix nanocomposites

The mechanical strength and wear behavior of Al–AlN metal matrix nanocomposites synthesized using melt metallurgy technique is investigated. Uniformly dispersed nanostructured AlN particulates in nanocomposites are found to improve the mechanical properties. Detailed study on compressive and tensile test is attempted in the present work to understand the mechanism of deformation in nanocomposites. Adhesive dry wear test results indicate that applied load has strong influence on wear behavior of nanocomposites compared to the sliding distance. Porosity and weak agglomeration of nanoparticles are found to significantly affect the wear behavior and mechanical strength of synthesized nanocomposites. It is revealed that the transfer of load from matrix to reinforcement particulate is not an instantaneous phenomenon but initiates after some incubation period depending on the fraction of porosity in nanocomposites during compressive and tensile testing.

Study on Quantification of Oxide Phases in Ex-situ AlN/Al Metal Matrix Nanocomposites

Al based metal matrix nanocomposite (MMNC) is synthesized by dispersing nanocrystalline aluminium nitride (AlN) particles in Aluminum matrix using ex-situ melt metallurgy method. The entrapment of atmospheric oxygen along with ex-situ particulate has been a long standing issue during fabrication of metal matrix composites. In the present investigation, presence of oxygen has been quantified in synthesized Al-AlN MMNCs with varying AlN content. The high resolution scanning electron microscopy is used to study morphology and distribution of AlN in Al matrix. Energy dispersive spectroscopy analysis is used to quantify in situ oxide phases along with AlN particles in the synthesized MMNCs using thermodynamic mass balance calculations. Present study also attempts to understand the role of in-situ oxide phases on the mechanical properties of MMNCs using microindentation hardness and nanoindentation test.

Nanoindentation studies of ex situ AlN/Al metal matrix nanocomposites

Nanocrystalline Aluminium nitride (AlN) powder is dispersed in different weight ratio in Aluminum matrix to fabricate metal matrix nanocomposite (MMNC) using ex situ melt metallurgy process. The synthesized Al–AlN nanocomposites are studied for phase analysis using high resolution scanning electron microscopy (FEG-SEM) and for hardness behavior using microindentation and nanoindentation tests. Quantitative analysis of the oxide phases is calculated from thermodynamic data and mass balance equation using elemental data obtained from energy dispersive spectroscopy (EDS) results. Role of oxide phases in association with AlN particles is investigated to understand the mechanical behavior of composites using nanoindentation tester. Load–displacement profile obtained from nanoindentation test reveals distribution of oxide phases along with AlN particle and their effect on indent penetration.

Corrosion Characterization of Al6061/Red Mud Metal Matrix Composites

Metal matrix composites are heterogeneous systems containing matrix and reinforcement. Their physical and mechanical properties can be tailored according to requirement. They are used in automobile, aircraft and marine industries because of their increased corrosion resistance. In this paper weight loss corrosion test, open circuit potential test and potentiostat test are conducted on AL6061/ Red Mud metal matrix composites in different concentrated neutral chloride solutions like sodium chloride solutions. Composites are prepared by liquid melt metallurgy technique using vortex method. Composites containing 2, 4 and 6 percent of red mud are prepared according to ASTM standards. Specimens are machined and made ready by standard metallographic methods. Weight loss corrosion studies, open circuit potential studies and potentiostat studies, are carried out in 0.035, 0.35 and 3.5% solutions of sodium chloride. The corrosion rate decreases with increase in the exposure time for all specimens in all corrodents in all the methods of testing. Corrosion rate also decreases with the increase in reinforcement content of the composites. Hence the composites can be used for the manufacture of the equipments used in marine environment so that they lost long.

Computer Simulations of Galvanic Corrosion Behaviour of Zinc –Aluminium Based Composites Reinforced with Red Mud by Potentiodynamic Polarization Techniques Leading to Corrosion Control

The present investigation aims to evaluate the corrosion control properties of metal matrix composites in comparison with matrix alloy using different concentration of Sodium chloride solutions and potentiodynamic polarization techniques. Matrix alloy used in ZA-27 and the reinforcement used was red mud particulates of size 50-80 microns. Composites are prepared by liquid melt metallurgy technique using vortex method. Red mud particulates reinforced varying from two to six percent by weight in steps of two percent under dry conditions. Specimens are prepared according to ASTM standards. Both composites and corresponding base alloys were subjected to identical test conditions to understand the influence of the reinforcement on alloy corrosion behaviour and effective corrosion control. Composites became less prone to corrosion and pit formation than the matrix alloy, which may be due to chemically inert red mud particles present in the metal matrix composites. On the other hand the test also reveals that corrosion resistance of both alloy and composites in crease with increase in normality of the sodium chloride solution, which may be due to increasing concentration of hydrogen ions in the solution. Corrosion of alloys can be effectively controlled by converting them in to composites by the addition of inert materials like silica particulates. If any automobile parts like bearing are made using these composites corrosion control properties can be tailored so that they can be used effectively in wide area of application.

Where reactive sintering beats melt technology

Bulk intermediary phases of titanium-aluminium and titanium-aluminium-silicon systems are promising materials for high-temperature applications. However, their production by melt metallurgy is problematic due to high melting points of the intermediary phases and high reactivity of the melt. Reactive sintering via powder metallurgy is a simple alternative to conventional melting processes, say Czech researchers…

Wear Resistant Steels and Casting Alloys containing Niobium Carbide

Niobium, like titanium and vanadium, forms superhard MC carbides that remain relatively pure in technical alloys on account of their low solubility for other metallic alloying elements. However, because they have a greater hardness than the precipitated chromium carbides commonly used in wear‐resistant alloys, they are suitable as alternative hard phases. This contribution deals with new wear‐resistant steels and casting alloys containing niobium carbide. These include a secondary hardening hardfacing alloy, a composite casting alloy for wear applications at elevated temperatures, a white cast iron as well as two variants of a corrosion‐resistant cold‐work tool steel produced by melt metallurgy and by powder metallurgy. A heat‐resistant casting alloy is also discussed. Based on equilibrium calculations the microstructures developing during production of the alloys are analysed, and the results are discussed with respect to important properties such as abrasive wear and corrosion resistance.

The Equilib-ARMAX approach to the dynamic modelling of the melt metallurgy in DC plasma arc smelting operations

A methodology is presented and evaluated to model the metallurgical dynamics of DC plasma arc smelting, using high carbon ferrochrome production as a case study. The model type is called an Equilib-ARMAX model as it integrates fundamental thermodynamic models with dynamic models. The Equilib-ARMAX model takes into account the inherently uncertain nature of smelter plant data, as well as the process dynamics and the moving chemical equilibrium target. The model structure, modelling performance, and model limitations of this model type are presented. The model could predict the metallurgical dynamics well within the inherent uncertainty of the process data.

Self-structuring of multicomponent materials in hydrogen-thermal treatment

Production of multicomponent materials with a stable homogeneity and desired chemical composition by the methods of melting metallurgy is still difficult if not impossible, due to the different temperature of melting and burning out of different elements. The application of methods of direct solid-phase synthesis, in particular, the hydrogen thermal treatment allows to create a new class of structure-formed materials (including those for welding production) of any required chemical composition and uniformly doped with alloying elements within the entire volume. The present work deals with the results of the examination of microstructure and chemical composition of granules of the multicomponent powder representing the mechanical mixture of nickel oxide and flux-forming components (oxides of metals and minerals) before and after the hydrogen-thermal treatment. It is shown that at certain conditions the process of the solid-phase synthesis takes place in the material, qualitatively changing the morphology of the initial powder. From the mechanical homogenized mixture the volumetric uniformly-repeating lamellar microstructure with a porous matrix and globular formations jointed with it, is formed, thus permitting to classify the given material as composite and the process of its formation as self-organizing.

The combustion synthesis of Ni-Ti shape memory alloys

Combustion synthesis is a new and promising method of producing Ni-Ti series shape memory alloys. It has the advantage of both time and energy savings compared with the conventional melting or powder metallurgy approaches. The value of the ratio ΔH∘ƒ,298/ Cp,298 plays a key role in this method, especially if a liquid product is required. Solidified products made by the combustion synthesis process were hot rolled into plates exhibiting the shape memory effect. It was discovered that shape memory transition temperatures can be tailored over a wide temperature range (from −78 to 460°C) by substituting a third element, such as palladium or iron, for nickel. This approach should greatly extend the application of such alloys.

Utilization of space shuttle external tank materials by melting and powder metallurgy

The Crucible Melt Extraction Process was demonstrated to convert scraps of aluminum alloy 2219, used in the Space Shuttle External Tank, into fibers. The cast fibers were then consolidated by cold welding. The X-ray diffraction test of the cast fibers was done to examine the crystallinity and oxide content of the fibers. The compressive stress-strain behavior of the consolidated materials was also examined. Two conceptual schemes which would adapt the as-developed Crucible Melt Extraction Process to the microgravity condition in space were finally proposed.

Aspects of the metallurgy of uranium and constructional metals

On the basis of foreign material presented at the Second International Conference on the Peaceful Uses of Atomic Energy (Geneva, 1958), we examine aspects of uranium production (reductive melting, casting, pressure treatment, and powder metallurgy); zirconium metallurgy (new data on the technological scheme, the nature of sponge and the dimensions of ingots); the production of the new constructional metals, niobium and vanadium (comparison of various methods for their preparation; metallothermal, vacuum carbo-thermal, electrolytic refining and the quality of production); the production of thin-walled beryllium tubes for fuel element sheaths; the use of zirconium hydride as a moderator and of zirconium-uranium-hydrogen alloys for fuel element cores.