Volume 55, Issue 2

Composites with a interpenetrated copper-ceramic microstructure can be customized for highest demands such as a high thermal conductivity in combination with a small thermal expansion. This article reports on the synthesis of near-net shape Cu-Al 2 O 3 composites via gas pressure infiltration. Open-porous Al 2 O 3 preforms are infiltrated with Cu using Si 3 N 4 permanent molds. The infiltration quality as well as the porosity distribution within the materials are described qualitatively and quantitatively. The effects of the manufacturing process and cooling rate on the composites will be looked at.

What is left of bronze age copper production and processing is predominantly the slags which were not processed any further and which archaeologists have found at various archaeological sites. It would be of particular interest to establish a correlation between the different types of slag and specific copper ores and stages of the copper production process. It proves rather difficult, however, to deduce the entire set of relevant initial parameters from the final product, the “slag”. The investigative results of three very different types of slag reveal the distribution of slag and that of the source materials quartz, copper ore and iron ore. In the slag areas, different distributions of its constituents olivine, wüstite and vitreous phase (wollastonite) were observed. From element analysis and plottings in the FeO-SiO 2 -CaO phase diagram, some first conclusions may be drawn as to the formation conditions with regard to the different types of slag.

During a minor inspection of a heavy-duty gas turbine engine, the hexagonal head of a bolt used for fixing a metal plate in the air intake was found on the floor of the air intake casing [1, 2]. The respective washer was not found. It is believed to have been ingested into the engine, having caused moderate compressor damage. The inspection was started after 83.500 operating hours. Only one fractured bolt was found. The subject bolt fractured due to stress corrosion cracking (SCC), induced by pitting corrosion and possibly assisted by crevice corrosion.