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We have synthesized a series of nanocrystalline ferrite samples with the composition Mnx Cu1-x Fe2O4 (x = 0.2, 0.4, 0.6, 0.8) by an advanced sol-gel auto-combustion method. The X-ray diffraction patterns confirm the existence of single-phase cubic spinel crystal structure of ferrites with lattice parameter ranges from 8.395 Å to 8.45 Å .We report the equilibrium radii for tetrahedral and octahedral sites in the unit cells and the estimated cation distribution over the two sites of nanocrystalline Mnx Cu1-x Fe2O4.We also estimate the oxygen positional parameter as 0.389. The positron annihilation life time spectroscopic studies were carried out for all the samples and analyzed the variation of life time parameters T1; I1, T2; I2 and the mean life time Tm to elucidate the defect structure of the nanocrystalline MnxCu1-xFe2O4. We found that the overall vacant type defects fill up as the Mn2+ ion concentration, x, increases. The value of T1 varies from 150 ps to 170 ps and that of T2 varies from 295 ps to 335 ps, which are the characteristic values for nanocrystalline samples, indicating the presence of intergranular as well as surface-diffused vacancies in the crystal structure. [ABSTRACT FROM AUTHOR]

Microstructural control through thermo-mechanical simulation has been attempted in aluminum-killed low carbon-manganese boron containing steel. The results from dilatometric studies were used to explain austenite decomposition characteristics under different soaking temperatures and cooling rates. A significant lowering in Ar3 temperature was observed when the steel was soaked at 1200°C followed by rapid cooling (20°C/sec). On the contrary, no appreciable change in Ar3 temperature was noticed when soaking temperature was brought down to 950°C. Hot rolling simulations were carried out both in austenitic and ferritic regions to understand microstructural evolution. Ferritic hot rolling at 750°C followed by coiling at 650°C exhibited formation of coarse recrystallized ferrite grains of 30 micron, which is ideally suited for cold forming and reducing applications. [ABSTRACT FROM AUTHOR]

Ferrite grain sizes of the order of 1 to 2 pm were obtained by optimizing the strain, strain rate, the stage of cooling, as well as the cooling rate during hot rolling of 0.15C-0.92Mn-0.01Si-0.036S-0.04P-0.013Nb steel. It was found that in single-pass rolling of a 10 mm plate to a thickness of 3.5 mm with an entry temperature of 800 °C, and early-stage water cooling, very fine grains of ferrite (1-2 µm) were formed at the surface and in subsurface regions. It was also found that the threshold level of reduction during rolling, which is required for the refinement of ferrite grains, is >50 %. The 3.5 mm thermomechanically processed plate was found to possess very attractive mechanical properties in terms of the yield strength (485 MPa), the ultimate tensile strength (UTS) (763 MPa), and particularly the yield strength to ultimate tensile strength (YS/UTS) ratio (0.63). This combination of properties can be explained on the basis of the composite microstructure consisting of ferrite and bainite that was obtained as a result of the thermomechanical processing. [ABSTRACT FROM AUTHOR]