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Raghavan V.,17 Jaganathan Road
Journal of Phase Equilibria and Diffusion | Year: 2010

A team of researchers investigated the aluminum-copper-iron (Al-Cu-Fe) system at a region of more than 40 at.% Al at 600 °C and carried out a detailed thermodynamic analysis. Investigations revealed that the solid solution γ based on face-centered cubic (fcc) Fe was restricted by a loop in the Fe-Al phase diagram. The solid solution based on the body-centered cubic (bcc) Fe (α) existed in the disordered A2 and ordered B2 and D0 3 formed. The high-temperature phase ε was stable between 1232 and 1102 °C and had the D8 2, Cu 5Zn 8-type cubic structure, with a = 0.89757 nm. There were also three other intermediate phases in the system with restricted ranges of homogeneity, such as FeAl 2(triclinic), Fe 2Al 5(orthorhombic), and FeAl 3 or Fe 4Al 13 (monoclinic). Source


Raghavan V.,17 Jaganathan Road
Journal of Phase Equilibria and Diffusion | Year: 2010

A team of researchers carried out a revised thermodynamic analysis of the aluminum-iron-nickel (Al-Fe-Ni) system, combining new calorimetric measurements of thermodynamic properties, first-principles calculations, and the CALPHAD approach. The Al-Fe phase diagram showed that the face-centered cubic (fcc) solid solution based on Fe was restricted by a γ loop. The body-centered cubic (bcc) solid solution existed in the disordered A2 form, along with the ordered B2 and D0 3 formed. The Fe-Ni phase diagram was characterized by a very narrow solidification range with a peritectic reaction at 1514 °C that yielded the Fe-based fcc solid solution. It was observed that a continuous fcc solid solution γ was stable over a wide range of temperature and that an ordered phase FeNi 3 formed congruently from it at 517 °C. Source


Raghavan V.,17 Jaganathan Road
Journal of Phase Equilibria and Diffusion | Year: 2010

Researchers investigated a liquidus projection in the FeO-Fe 2O 3-SiO 2 region, three isothermal sections at 1600, 1200 and 900°C and a reaction sequence. The activities of ZnO in the ZnO-SiO 2 system between 800 and 700°C were determined from emf measurements. The phases were identified with x-ray powder diffraction and the phase compositions were measured with electron probe microanalyzer (EPMA). The activities of FeO and ZnO in the four-phase equilibrium of FeO + Fe 2SiO 4 + Zn 2SiO 4 + (Fe) were found to be 0.93 and 0.53 respectively. Another experiment investigated pelletized powder mixtures of Fe 2O 3, SiO 2 and ZnO, annealed them in air between 1450 and 1200°C, followed by quenching in iced water. The microstructures were examined with optical and scanning electron microscopy. Source


Raghavan V.,17 Jaganathan Road
Journal of Phase Equilibria and Diffusion | Year: 2010

Fe-Ni-O (Iron-Nickel-Oxygen) ternary system was reviewed by several researchers. In the Fe-Ni phase diagram, a continuous face-centered cubic (fcc) solid solution forms between γFe and Ni and is stable over a wide range of temperature. Scientists prepared pellets under pressure with starting powders of 99.98% Fe 2O 3, 99.99% NiO, 99.99% Fe, and 99.8% Ni. Two methods of equilibration were used, gas/oxide equilibrated in open systems at fixed oxygen partial pressures, which were obtained by flowing known proportions of CO/CO 2 gas mixtures through the tube furnace, and oxide/alloy mixtures equilibrated in closed systems. Microstructures were examined with optical and scanning electron microscopes. The phase compositions were measured by an electron probe microanalyzer and listed. Factsage software was used to calculate the phase equilibria for comparison with the experimental results. It was observed that the non-stoichiometry of the spinel phase increases with temperature. Source


Raghavan V.,17 Jaganathan Road
Journal of Phase Equilibria and Diffusion | Year: 2010

A study was conducted to investigate the formation of the aluminum-magnesium-manganese (Al-Mg-Mn) compound. The Al-Mn phase diagram depicted a number of intermediate phases. A diffusion couple of Mn with a 55Mg-45Al master alloy and the four ternary alloys were annealed at 400 °C for 446 or 672 h and quenched in water. The annealing experiments revealed tie-lines between (Mg) and (βMn) (Mg) and (βMn) and between (Mg) and Al 11Mn 4(LT), but not between (Mg) and the intervening Al-Mn phase Al 8Mn 5. This was attributed to the very slow formation of Al 8Mn 5 and included this phase in the isothermal section. Source

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