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New experimental data are reported relative to the development of banded structures in Mn-segregated Dual Phase steels during the austenite-to-ferrite transformation stage of their final heat treatment. Two types of ferrite are detected to grow simultaneously, i.e. allotriomorph and acicular ferrite, with distinct consequences on the topology of the final (ferrite + martensite) microstructure: allotriomorph ferrite sharpens the banded structure of ferrite and martensite between Mn-poor and Mn-enriched regions, respectively, whereas acicular ferrite favours more isotropic microstructures. Owing to an original image treatment procedure, the sharpness of banded structure is quantitatively analyzed for different heat treatment conditions. Results confirm those of previous works, but we propose to rather explain them by considering that a change in a heat treatment parameter results in a variation in the respective amounts of both ferrite types. [ABSTRACT FROM AUTHOR]

Abstract: The influence of different heat treatments on the magnetic and magnetoelastic properties of highly magnetostrictive CoFe2O4 has been investigated. The first order cubic anisotropy coefficient, coercive field, magnetostriction and high strain sensitivity were observed to decrease as the heat treatment temperature increased. The saturation magnetization of the samples on the other hand increased with increase in heat treatment temperature. These changes were not accompanied by any observable changes in crystal structure or composition and are indicative of migration of Co2+ from the octahedral sites (B-sites) to the tetrahedral sites (A-sites) and Fe3+ from the A-sites to the B-sites of the spinel structure. Different distributions of the cations at the two distinct lattice sites can strongly affect the magnetic and magnetoelastic properties of these materials. [Copyright &y& Elsevier]