An investigation of nitride precipitates in archaeological iron artefacts from Poland.

The paper describes the investigations of nitride precipitates in a spearhead and a sword found in the territory of Poland, in cremation graveyards of the Przeworsk Culture, dated to the Roman Period. Three different techniques of the examination of nitride precipitates were employed: optical microscope, scanning electron microscope (scanning electron microscope with energy dispersive X-ray spectrometer) and transmission electron microscope. Two types of precipitates have been observed, and their plate-like shape was demonstrated. The large precipitate has been confirmed to be gamma'-Fe(4)N, whereas the small one has been identified as alpha''-Fe(16)N(2). The origin of nitride precipitates in archaeological iron artefacts from Poland is probably a result of the manufacturing process or cremation as part of burial rites. An examination of available iron artefacts indicates that nitride precipitates (have only limited effect on mechanical properties) influence the hardness of metal only to a very limited degree.

TEM studies of melt-spun alloys with liquid miscibility gap.

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.

Transmission electron microscopy study of crystallization in Fe-Si-B-Cr-C amorphous alloy.

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.