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Presents a study which examined the substitution of 3d transition elements iron and nickel in the yttrium barium[sub2]copper[sub3]oxygen[sub7-δ]. Experimental details; Results; Discussion and conclusions.

Examines the critical properties of iron (Fe)-substituted YBa[sub2]Cu[sub3]O[sub7-8]. Classes of defects and inhomogeneities that have been considered as possible pinning sites; Role of twin boundaries for the critical currents in the cuprate superconductors; Changes in the microstructure of Fe-substituted samples.

Commercial purity aluminum was deformed by equal channel angular pressing (ECAP) using steel dies producing two different shear strains of either 1.15 or 0.60 in each pass. Two sets of samples were selected for study, of which the first set consists of aluminum billets repeatedly deformed without changing orientation (process A) up to three passes using first die. The second set of samples was equal channel angular pressed (ECAPed) using the second die up to 10 passes adopting process Bc, where samples were rotated by 90 deg between successive passes. The flow patterns were revealed by optical metallography. Tensile strength and hardness were measured. The ECAPed samples were isochronally-annealed and recrystallization behavior was studied by microscopy and Vickers hardness measurements. Refinement of grain size, substructure, and texture was studied by transmission electron microscopy (TEM) and orientation imaging microscopy (OIM). The results show that flow patterns are complex and distinct from simple shear. Strain is higher at the outer surfaces, highest at the bottom surface, and intermediate in the middle of the billet. The work piece strain hardens significantly in first pass with an attendant drop in ductility. The degree of strengthening reduces in subsequent passes. The high defect density introduced during the initial passes leads to grain refinement to an ultrafine level and advantageously the material regains ductility. The refinement in microstructure obtained after two to three passes is stable up to 250 °C. The flow patterns are very similar to those obtained by physical modeling in our earlier studies using plasticine. Equiaxed ultrafine-grained structure (average grain size = 0.53 μm) was obtained after ECAP at an equivalent shear strain of 6.0. [ABSTRACT FROM AUTHOR]

The stability of a lamellar structure consisting of α2 and γ phases in alloys Ti-48Al, Ti-48Al-2Mo, Ti-48Al-4Nb, and Ti-48Al-1Mo-4Nb has been studied as a function of aging time and temperature. The alloys were solution treated (1400 °C, 30 min, and air-cooled (AC)) and aged at 1000 °C and 1100 °C for 1, 4, and 16 hours, respectively. The results indicate that the kinetics of lamellae to equiaxed transformation depends on alloy chemistry, aging time, and temperature. The Nb decreases and Mo increases the kinetics of transformation. The combined effect of Nb and Mo results in the highest volume fraction of equiaxed microstructure at a given aging time and temperature. The results have been discussed in relation to microstructural features and have been compared with those reported in other α2 + γ alloys. [ABSTRACT FROM AUTHOR]

Procedures for preparation of Lauha Bhasma are described in ancient texts of Ayurveda. These procedures also begin with different source material for iron such as Teekshna Lauha and Kanta Lauha etc. In the present study, we have selected different source materials viz. magnetite iron ore for Kanta Lauha and pure (Armco grade) iron turnings for Teekshna Lauha. The standard procedures of preparation of Lauha Bhasma are carried out in identical conditions for these two raw materials. The final product from the Puta are characterized by using X-ray diffraction and X-ray fluorescence spectroscopy to understanding the crystallographic form or forms of iron oxides and their composition at the end of each Puta. The iron content at the end of repeated Putas (18 for Kanta Lauha and 20 for Teekshna Lauha) have shown a decrease in case of Teekshna Lauha since the starting material is pure iron while it showed only marginal decreases in the case of Kanta Lauha because the Fe3O4 of magnetite is undergoing oxidation to Fe2 O3. The trace elements remain within the Bhasma in the form of various oxides of Si, Al, Ca, etc. [ABSTRACT FROM AUTHOR]

Differently prepared samples with the nominal composition Y1.2Ba0.8CuOy are examined via microscopy, energy dispersive x-ray analysis, x-ray diffraction, and measurements of resistivity and susceptibility. Various phases are identified directly. Essentially these are Y2BaCuO5, which forms a matrix with semiconducting and antiferromagnetic properties and YBa2Cu3O7-x, which is present in a dendritic morphology. The dendritic appearance indicates that YBa2Cu3O7-x is formed by nucleation and growth during sintering. Despite the particular growth mechanism of sintered materials a strong analogy exists with dendritic growth during solid-state transformations in metallic alloys. [ABSTRACT FROM AUTHOR]