(Table 1) Chemical analyses of rock samples from low atolls of the Western Indian Ocean

Compositions, structures, and microstructures of different types of phosphorites and poorly phosphatized rocks from low atolls in the near-equatorial part of the Western Indian Ocean are described. The rocks were examined under optical and scanning microscopes using microprobe techniques and etching of selected samples with weak solvents as well as with the help of chemical analyses. It is proved that phosphorites have been formed owing to the uneven phosphatization of primary carbonate rocks; degree of their phosphatization ranges from traces to 40% P2O5. In the phosphorites numerous organic remains were encountered; they included fragments of plankton, debris of tortoise shells, and coccoidal and filamentous bacteria-like formations. It is suggested that the phosphorites formed due to high local biological productivity over the outer edges of coral reefs and are not related to guano accumulation or to endoupwelling.

Synchrotron strain scanning for residual stress measurement in cold-drawn steel rods

Cold-drawn steel rods and wires retain significant residual stresses as a consequence of the manufacturing process. These residual stresses are known to be detrimental for the mechanical properties of the wires and their durability in aggressive environments. Steel makers are aware of the problem and have developed post-drawing processes to try and reduce the residual stresses on the wires. The present authors have studied this problem for a number of years and have performed a detailed characterization of the residual stress state inside cold-drawn rods, including both experimental and numerical techniques. High-energy synchrotron sources have been particularly useful for this research. The results have shown how residual stresses evolve as a consequence of cold-drawing and how they change with subsequent post-drawing treatments. The authors have been able to measure for the first time a complete residual strain profile along the diameter in both phases (ferrite and cementite) of a cold-drawn steel rod.