Band 46, Heft 12

Kurzfassung Die Ausbildung des Gussgefüges hat einen signifikanten Einfluss auf die mechanischen Eigenschaften von Gussteilen. Durch eine gezielte Einstellung der Abkühlgeschwindigkeit wie z.B. durch die Wahl des Gießverfahrens und durch Schmelzebehandlungsmaßnahmen lassen sich positive Effekte erreichen. Die vorliegende Arbeit gibt einen Überblick über die Gefügeausbildung von Aluminium-Silicium-Gusslegierungen und über den Einfluss verschiedener Parameter wie Abkühlgeschwindigkeit, Gießverfahren, Veredelung und Kornfeinung.

The development of the oil and gas industry in Brazil in the last decades has led to petroleum extraction in deeper water and extremely corrosive environments, associated to the presence of H 2 S, CO 2 and chlorides, as well as mechanical loads caused by the wave's movement and sea streams. In these adverse conditions the search for new materials with adequate properties for this kind of application is intense. In the present work a study is carried out on the microstructure and mechanical properties of the super alloy Inconel 718 subjected to different temperatures and times of solution and aging heat treatments. This material, usually used in the fabrication of aircraft motor and energy generation turbines, in the present case is proposed for the fabrication of bolts used in the fixation of submarine pipes for oil extraction. The use of techniques like optical microscopy, automatic image analysis, scanning electron microscopy (SEM) and hardness and tensile tests, allowed the identification of the ideal conditions for heat treating this material for this kind of application.

Rapidly solidified ribbons of Cu-0.7 at.% Zr alloy have been produced by the melt spinning process. An overall assessment of the ribbons shows that the microstructure consists of two morphological zones: a zone with columnar grains at the wheel side and a zone with fine equiaxed grains at the top side of the ribbons. The columnar zone consists of fine Cu-Zr intermetallic particles inside the grains, while in the equiaxed zone we have fine precipitates inside the grains and coarser ones at their boundaries. Transmission electron microscopy was carried out to quantify the coarsening process of the particles. Analysis of particle size showed that the grain boundary particles coarsened noticeably faster than the particles within the copper grains, which coarsened in both morphological zones by bulk diffusion, controlled by the diffusivity of zirconium, and r 3 —t relationship was obtained at all temperatures of the experiment.