Showing papers in "Journal of Mining and Metallurgy, Section B in 2002"
TL;DR: A series of quaternary platinum-based alloys have been demonstrated to exhibit the same two-phase structure as Ni-based superalloys and showed good mechanical properties as mentioned in this paper.
Abstract: A series of quaternary platinum-based alloys have been demonstrated to exhibit the same two-phase structure as Ni-based superalloys and showed good mechanical properties. The properties of ternary alloys were a good indication that the quaternary alloys, with their better microstructure, will be even better. The quaternary alloy composition has been optimised at Pt84:Al11:Ru2:Cr3 for the best microstructure and hardness. Work has begun on establishing a thermodynamic database for Pt-Al-Ru-Cr alloys, and further work will be done to enhance the mechanical and oxidation properties of the alloys by adding small amounts of other elements to the base composition of Pt84:Al11:Ru2:Cr3.
18 citations
TL;DR: In this article, the experimental data were proceeded statistically and mathematical models were derived for the alloy properties such as tensile strength, electrical conductivity and elongation of the wires during TMT.
Abstract: A commercial Al - 0.62%Mg - 0.57%Si was thermomechanically treated (TMT). The TMT process included solution treatment, room temperature preageing, drawing (e=95%) and final ageing. The experimental data were proceeded statistically and mathematical models were derived for the alloy properties such as tensile strength, electrical conductivity and elongation of the wires during TMT. The models are used to find out the area of compromise optimal combination of the alloy properties. Higher final ageing temperature and time are required to design a TMT process for production of a long-term pre-aged wires. The influence of the room temperature preageing on the precipitation process during TMT is discussed.
12 citations
TL;DR: A survey of the most relevant processes from this domain by the end of 2000, which display a constant increase in the modern process metallurgy is presented in this article, showing that insufficient availability and the high price of the coking coals have forced many countries to research and adopt the non-coke-consuming reduction and metal manufacturing processes.
Abstract: For quite a long time efforts have been made to develop processes for producing iron i.e. steel without employing conventional procedures - from ore, coke, blast furnace, iron, electric arc furnace, converter to steel. The insufficient availability and the high price of the coking coals have forced many countries to research and adopt the non-coke-consuming reduction and metal manufacturing processes (non-coke metallurgy, direct reduction, direct processes). This paper represents a survey of the most relevant processes from this domain by the end of 2000, which display a constant increase in the modern process metallurgy.
12 citations
TL;DR: In this paper, the notion of heat is thoroughly analyzed and its historical links are searched particularly with relation to both the Greek philosophy (Milesians, Pythagoreans, atomists, etc.) and in the present day thermal physics.
Abstract: The notion of heat is thoroughly analyzed and its historical links are searched particularly with relation to both the Greek philosophy (Milesians, Pythagoreans, atomists, etc.) and in the present day thermal physics. Fluctuation, spontaneity and chaos are discussed. Thermodynamics is reviewed in the relation to both the traditional development and the modern description of disequilibria (open systems). Effect of dissipation is shown often to provide new, self-organized structures. Exploitation of fire and its conscious use as a manufacturing power are analyzed in terms of generalized engines to act in the sense of the information transducers.
10 citations
TL;DR: In this paper, the structural energy differences for end-members in the metastable or unstable structures are obtained by means of first-principles electronic structure calculations, based on the two-sublattice model.
Abstract: The first principles computations of the total energies of complex phases have been addressed recently. The structural energy differences, calculated by FLAPW (Full potential augmented plane wave) method, enable us to utilize a more complete physical information about total energy of intermetallic phases and to propose a new model for their thermodynamic description. Our approach is based on the two-sublattice model, similarly as for solid solution phases, but the structural energy differences for end-members in the metastable or unstable structures are obtained by means of first-principles electronic structure calculations. Phase diagrams of Fe-Cr and Co-Cr systems containing the intermetallic sigma-phase (5 inequivalent lattice sites, 30 atoms in repeat cell) are described here as an example of application of our new model.
10 citations
TL;DR: The need for a concerted multi-disciplinary approach in the investigation of intermetallic systems and the role of thermochemistry are underlined in this article, and the activity carried out in the Author's laboratory in the alloy thermodynamics is summarized.
Abstract: The need of a concerted multi-disciplinary approach in the investigation of intermetallic systems and the role of thermochemistry are underlined. The activity carried out in the Author’s laboratory in the alloy thermodynamics is summarized. The different instruments (calorimeters) built in laboratory are briefly presented and their performance discussed. The results obtained in the measurement of the enthalpy of formation mainly of several rare earth alloys are described. The characteristics of the Eu and Yb thermochemistry and crystallochemistry are finally underlined.
9 citations
TL;DR: The results of thermodynamic analysis of arsenic, antimony and bismuth distribution between copper matte and discard slag in reverberatory smelting at 1573 K are shown in this paper.
Abstract: The results of thermodynamic analysis of arsenic, antimony and bismuth distribution between copper matte and discard slag in reverberatory smelting at 1573 K are shown in this paper. On the basis of chemical analysis of the melt samples taken during stable operation of the reverb furnace No.2 in the Copper Smelter and Refinery, RTB Bor (Yugoslavia), the distribution coefficients of As, Sb, and Bi between copper matte and slag are calculated. The influence of the matte grade on the minor element distribution coefficients between copper matte and slag is also analyzed, as well as arsenic, antimony and bismuth distribution in slag.
8 citations
TL;DR: In this paper, the gallium activity from 950 to 1150K in the entire composition range of liquid Ga-Pb alloys was measured in an electrochemical cell with zirconia as solid electrolyte.
Abstract: EMF measurement of the electrochemical cell with zirconia as solid electrolyte was performed to determine the gallium activity from 950 to 1150K in the entire composition range of liquid Ga-Pb alloys. In the whole concentration range, activity of Ga shows moderately positive deviations from ideality, and activity of Pb which is derived by Gibbs- Duhem equation shows also positive deviation from ideality. These are compared with published data obtained by different experimental methods.
7 citations
TL;DR: In this article, the effect of temperature, time and presence of coke as reducer on the degree and mechanism of MeSO4 dissociation was investigated in the industrial production of nonferrous metals for explaining the processes that take place in the reduction of zinc and lead cakes.
Abstract: MeSO4 (Me = Fe, Co, Ni) dissociation is investigated in order to estimate the effect of temperature, time and presence of coke as reducer on the degree and mechanism of dissociation. It is proved that the presence of coke decreases the dissociation temperature considerably and increases the degree of MeSO4 dissociation. Based on the obtained experimental data, a mechanism of the processes is proposed. The obtained results can be used in the industrial production of non-ferrous metals for explaining the processes that take place in the reduction of zinc and lead cakes in order to achieve favorable environmental, technical and economic results.
6 citations
TL;DR: In this paper, the effect of natural aging and 95% cold deformation on the microstructure evolution and aging characteristics in commercial Al-1 mass % Mg2Si alloy subjected to thermomechanical treatment (TMT) was examined.
Abstract: The effect of natural aging and 95% cold deformation on the microstructure evolution and aging characteristics in commercial Al - 1 mass % Mg2Si alloy subjected to thermomechanical treatment (TMT) was examined. Transmission electron microscopy observations, tensile tests and electrical conductivity measurements were carried out in order to correlate microstructural features to properties on each TMT step. It was established that pre-aging at room temperature affected the morphology of dislocation structure induced by next cold deformation. The observed transition from cellular to homogenous dislocation distribution was explained by the different stability of zones produced by pre-aging of different duration. Natural aging suppressed recovery processes during post-deformation artificial aging, especially after prolonged storage after quenching and at lower aging temperature. It influenced the morphology of precipitates produced by post deformation artificial aging also. The overall effect of TMT involving prior-deformation natural aging in the scheme, on hardness, tensile properties and electrical conductivity is discussed based on experimental microstruture observations.
6 citations
TL;DR: In this article, two different reducers were used, namely dissolved NaHSO3 and gaseous SO2, and the degree of conversion was determined as a function of time from the weight of the sediment, and can be described by Avrami-type equation.
Abstract: Selenium crystallization process from aqueous solutions was investigated at constant temperature of 357 K. Two different reducers were used, namely dissolved NaHSO3 and gaseous SO2. Experiments were conducted for solutions with different initial selenium concentration and different pH. The degree of conversion was determined as a function of time from the weight of the sediment, and can be described by Avrami-type equation of the following form: - ln ( 1 - a) = (6.95 . 10 -3 . t )1.52 valid at constant temperature of 357 K for NaHSO3 reducer, rate constant k = 6.95.10-3 min-1, and t in minutes. When the reduction was carried out in SO2 stream, the rate constant k was found to be strongly dependent on the flow rate. Possible mechanism of the reduction process and the influence of the rate of the reduction on the morphology of the product were suggested.
TL;DR: In this article, the authors applied interstand and afterdeformation cooling of coiled and reinforcing bar steel in the accelerated cooling installations behind the prefinishing and finishing stands of the light-section mill.
Abstract: The work deals with application of interstand and afterdeformation cooling of coiled (∅10, 12 mm) and reinforcing (∅14,16 mm) bar steel in the accelerated cooling installations behind the prefinishing and finishing stands of the light-section mill which provides the formation of the even fine-grained ferrite-perlite structure and reduces grain growth in the mid section of the coil. The application of the roll stock interstand cooling behind the 11 th stand together with the afterdeformation accelerated roll stock cooling to 800-850 0 C enabled us getting reinforcing bar steel diameter ∅14mm with high impact strength..
TL;DR: In this article, the thermodynamic activity of indium in the solid Cu-In alloys was obtained from the EMF measurement of cell: In,In2O3, ZrO2(+11mol%CaO), Cu-IN,In 2O3 for 16 alloys in the temperature range 773 to 900K.
Abstract: The thermodynamic activity of indium in the solid Cu-In alloys was obtained from the EMF measurement of cell: In,In2O3, ZrO2(+11mol%CaO), Cu-In,In2O3 for 16 alloys in the temperature range 773 to 900K. Activity changes with composition at 823K are very large in the and - phase regions. Activity and free energies of formation are derived and compared with the published data.
TL;DR: In this paper, the partial vapour pressure of mercury over liquid Hg-Tl liquid solutions was determined in the temperature range from 450 to 700 K by direct vapor pressure measurements carried out with the quartz gauge.
Abstract: The partial vapour pressure of mercury over liquid Hg-Tl liquid solutions were determined in the temperature range from 450 to 700 K by direct vapour pressure measurements carried out with the quartz gauge. From the measured ln pHg vs.T relationships activities of mercury were determined. Using Redlich-Kister formulas logarithms of the activity coefficients were described with the following equations:
TL;DR: In this article, the influence of temperature and deformation degree on changes in the metal grain growth of drawn copper tubes was observed, and the results showed that after drawing with high cold deformation degrees (96 − 99 %), the annealing leads to the changes in continuous grain growth with increased temperature.
Abstract: This work gives results of influence of temperature and deformation degree on changes in the metal grain growth of drawn copper tubes, because this mutual dependence was observed. Copper tubes samples, chemical content of 99,97 % Cu and 0,024 % P, were exposed to recrystallized annealing after drawing. The annealing was carried out at temperatures of 573, 623, 673, 723, 773, 823 and 873 K, for 60 minutes, in laboratory conditions. Investigation results show that after drawing with high cold deformation degree (96 – 99 %), the annealing leads to the changes in the continuous grain growth with increased temperature. The smaller grain size appears at 823 K in comparison with the lower annealing temperature. Annealing has influence on mechanical characteristics of tested samples and during drawing of copper tubes these characteristics are adequately changed: with regard to the annealing at the 773 K, the characteristics of strength and plasticity increase as a result of decreased grain size. The increase of annealing temperature to 873 K leads to the increased grain size and decreased values of strength and plasticity characteristics.
TL;DR: In this article, the authors used melting point depression method and Zhang-Chou method for Ga-Cd and Cu-Pb binary systems with phase diagrams involving two liquid or solid coexisting phases.
Abstract: Calculations of activities in Ga-Cd and Cu-Pb binary systems were done based on their known phase diagrams, using different calculation methods. First, activities of cadmium at 700 K and copper at 1263 K in Ca - Cd and Cu - Pb systems, respectively, were calculated by melting point depression method and Zhang-Chou method for binary systems with phase diagrams involving two liquid or solid coexisting phases. In order to obtain activity values in the entire composition range, these methods were applied in the definite parts of composition range in both investigating systems. The same procedure was done, using modified Rao- Belton method by Chou, who used Richardson assumption. Activities of the second component in both investigating systems were calculated by use of Gibbs-Duhem equation. All calculated results were compared with literature data and mutual comparison between applied methods was done.
TL;DR: In this paper, a model for the mullite formation from kaolinites and the solid-solution range of mullite in the Al2O3-SiO2 system has been evaluated.
Abstract: A model for the mullite formation from kaolinites and the solid-solution range of mullite in the Al2O3-SiO2 system has been evaluated. This rather complicated model implies that both octahedral and tetrahedral coordinated Al3+-ions as well as tetrahedral Si4+-ions participate together with O2-ions and vacant oxygen positions during the rearrangements in the structure during the sintering process at high temperatures.
TL;DR: In this article, the importance of experimentation as an ingredient to CALPHAD assessments is brought out in the case of a number of metallic and oxidic systems, and two types of experimental techniques have been used in the present laboratory for thermodynamic studies.
Abstract: The importance of experimentation as an ingredient to CALPHAD assessments is brought out in the present paper and is illustrated in the case of a number of metallic and oxidic systems. Two types of experimental techniques have been used in the present laboratory for thermodynamic studies, and the details are presented. The results obtained together with the assessed phase diagram in the case of a few selected systems are presented. It was shown that careful experimentation has brought new features in the case of carbide systems involving Mn, and a new 4-phase equilibrium in the case of Ni-W-O system. New data with regard to the thermodynamic activities of FeO-containing slag systems and sulphide capacities of multicomponent slags, obtained by gas equilibration method, are also presented. A thermodynamic software, THERMOSLAG © based on the experimental data has been found to be extremely useful by the steel industries is also discussed.
TL;DR: In this article, the corrosion resistance of Cr - Ni (special steels) specimen is tested by electrochemical methods, numerical method of linear polarization and polarization resistance method in calcium-hypochlorite (Ca(OCl)2) solutions.
Abstract: Corrosion resistance of Cr - Ni (special steels) specimen is tested by electrochemical methods, numerical method of linear polarization and polarization resistance method in calcium-hypochlorite (Ca(OCl)2) solutions. With increasing of Ca(OCl)2 concentration, pH value of the solution increases, as well as active chlorine concentration and corrosion activity of the medium. According to the quantitative method of the corrosion resistance determination it can be concluded that the steels tested in 1 wt % Ca(OCl)2 solution are resistant, in 10 wt % solution constant, and in 50 wt % suspension less resistant. URANUS B6 showed the best corrosion resistance of all tested chromium - nickel steels in all tested corrosion mediums.
TL;DR: In this paper, the thermal behavior of ZnO powder obtained by ultrasonic spray pyrolysis of nitrate solution (c=0.8mol/dm3, D0=2.695µm, Tmax=6000C, FG=1.2dm3/min) was investigated using non-isothermal differential scanning calorimetry (DSC, heating rates 5, 10, 15, 20O/min).
Abstract: The thermal behavior of ZnO powder obtained by ultrasonic spray pyrolysis of nitrate solution (c=0.8mol/dm3, D0=2.695µm, Tmax=6000C, FG=1.2dm3/min) was investigated using non-isothermal differential scanning calorimetry (DSC, heating rates 5, 10, 15, 20O/min). The exothermic heat effects at the temperature range from 350 to 5000C were linked to particles structural data obtained by XRD, SEM and TEM analysis. Produced particles are characterized by uniform submicronic size (D=800nm, BET=4.94m2/g), high phase purity and granular or circular “open” surface due to the presence of primary crystallites (d= 20nm). Observed structural changes during heating of this powder were attributed to simultaneous processes of nucleation and growth of primary crystallites inside the produced particles.
TL;DR: In this article, the shape of potentiodynamic curves depends mainly on the composition of investigated alloys, but also on the electrolyte used in experiments, and it was established a catalytic effect of cupric ions present in electrolyte on oxidation of gold and 18 k gold alloys.
Abstract: The shape of potentiodynamic curves depends mainly on the composition of investigated alloys, but also on the electrolyte used in experiments. In this work investigation were performed for pure gold, and pure silver and copper as alloying metals, then for binary alloys Au-Ag and Au-Cu containing gold as in 18 k gold (i.e. 75 % Au) and Ag-Cu with mass ratio 1:1 and, finally, for three component 18 k gold. It was established a catalytic effect of cupric ions present in electrolyte on oxidation of gold and 18 k gold alloys.
TL;DR: In this article, the authors have presented Computational thermodynamics and informational technologies in the field of computer desing of materials as well as appliance of CALPHAD method on resolution of thermodynamic problems.
Abstract: Computational thermodynamics and informational technologies in the field of computer desing of materials as well as appliance of CALPHAD method on resolution of thermodynamic problems are presented in this paper.