Volume 45, Issue 3

The use of iron based materials in building of highly decorated pavilions, rotundas and large constructions reached its zenith in the second half of the 19th century. Over the following century, due to atmospheric corrosion, many of these historical objects disintegrated so badly that they needed urgent attention from conservation. The present study was set up to examine the metallurgical features of two famous buildings — the Palm House in the Botanic Garden in Adelaide, South Australia (S. A.) and the Band Rotunda in Kosice City in Slovakia, allowing some rules for reconstruction to be laid down. In both cases, the ‘iron based’ construction material and ornaments investigated were made in Germany at the end of the 19th century.

Kurzfassung Das Ziel der Untersuchungen bestand in der Erarbeitung grundlegender Erkenntnisse über mikrostrukturelle Veränderungen im technologischen Prozessablauf der Metallschaumherstellung nach dem schmelz-pulvermetal-lurgischen Verfahren. Dazu war eine exakte Gefügecharakterisierung in allen technologischen Stufen notwendig. Übliche metallografische Präparationen waren wegen der leicht flüchtigen Komponenten der Treibmittel sowie der locker gepressten Pulver mit entgegengesetzten Eigenschaften nicht realisierbar. Mit dieser Arbeit wurden Möglichkeiten der Ionenstrahlpräparation erarbeitet, mit denen die Gefüge und insbesondere das Treibmittel in allen technologischen Stufen (Pulvermischung, Blöcke, Stränge, Metallschaum) exakt dargestellt werden konnten.

Aluminum-copper alloy EN AW 2017 (Al-3.9Cu-0.6% Mn-0.7%Mg) based composite powders reinforced with 5 and 15 vol. % SiC particulates were produced by high energy ball milling (HEM) process. The milling times range between 10 min and 6 h. After milling for a certain time, i.e., 2 h, the cellular structure of CuAl 2 intermetallic particles initially present in the matrix and precipitate at the grain boundaries that were destroyed and distributed along the deformation axis. XRD results clearly showed that the X-ray diffraction peaks of CuAl 2 disappear after 2 h milling time suggesting that the submicrometer sized intermetallic CuAl 2 particles dissolved into the aluminum matrix. This was also confirmed by SEM investigation. During subsequent milling of composite blends (2 h and more) the reinforcement particles were heavily fragmented. Thus they exhibited a significant reduction in size. The results indicate that the particle size of SiC and CuAl 2 was refined greatly after 6 h of high energy ball milling. However, it is clear that the particle size distribution even after the longest period of milling, 6 h, showed no significant narrowing. The crystallite size of the composites was reduced to below 45 nm which was confirmed by X-ray line broadening analysis.