RESUMO
The work presents the microstructure characterization of the new (Fe, Ni)-Cu-(P, Si, B) melt-spun glass forming alloys investigated by means of transmission electron microscope. The results are compared with the data obtained by other complementary methods such as XRD and Mössbauer spectroscopy. The phases occurring during the crystallization of the glassy matrix are identified and characterized in terms of a long-range order and a short-range order. The thermal stability of the alloy is characterized by differential scanning calorimetry. The study describes the mechanical and magnetic properties of the new alloys at room temperature as well as characteristics resulting from heating the as-cast melt-spun alloy at elevated temperatures. The changes of the properties of the alloy at elevated temperatures are correlated with the microstructural changes.
RESUMO
The microstructures of the Fe-Cu-based alloys melt-spun from various temperatures are presented. Two compositions, with different Fe and Cu content, revealing liquid miscibility gap, were studied. Nonuniform, large-elongated areas were observed for lower melt-spinning temperatures, indicating liquid/liquid phase separation in the crucible before cooling. An increase of the melt ejection temperature, followed by rapid cooling, brought about precipitation process within homogeneous melt. Studies of the system with higher Fe content proved amorphous nature of the matrix and crystalline structure of the primary formed Cu-rich precipitates. Moreover, generations of the secondary spherical particles, precipitated within the previously formed Cu-rich melt, were observed. The microstructure of the melt-spun alloy with a higher Cu content, on the other hand, consisted of the Fe-rich amorphous spherical particles formed during cooling of the Cu-rich liquid. The precipitation of the secondary Cu-rich particles in the primary formed Fe-rich was also observed.
RESUMO
The crystallization behaviour of Fe(72)Si(9.1)B(14.8)Cr(2.2)C(1.9) alloy was studied. Three forms of the examined alloy were studied: water-atomized powder, as-spun ribbon and fully crystallized ribbon. Transmission electron microscopy studies of the examined alloy in the form of powder revealed partial crystallization of Fe(2)B. The as-spun ribbon was found to be fully amorphous, and no evidence of any crystalline phases was detected. Formation of metastable phases in the fully devitrificated ribbon was observed. The examined alloy, heated to above its crystallization temperature, consisted of alpha-Fe(3)(Si), Fe(23)(C,B)(6), Fe(3)B and Fe(2)B crystalline phases.
