Aircraft front fastening plate VHS-497 (2)
Marianne. Senn (EMPA, Dübendorf, Zurich, Switzerland) & Christian. Degrigny (HE-Arc CR, Neuchâtel, Neuchâtel, Switzerland)
Metal fastening plate for the wooden construction of the front of the aeroplane, broken by use (Fig. 1).
Aeroplane part
Dufaux IV aeroplane
Biplane built by Henri and Armand Dufaux in 1909/10
Modern Times
Outdoor to indoor atmosphere
Swiss Museum of Transport, Luzern, Lucerne
Swiss Museum of Transport, Luzern, Lucerne
VHS-497 (2)
Not known
Nothing to report.
Stratigraphic representation: none.
The top part has been cut during sampling (Fig. 2). The more regular right side is the plate surface and the irregular side is the broken edge (Fig. 3). Dimensions: L = 4mm ; W = 4mm.
Al Cu Sn Zn Si Alloy
As-cast
DUF-4
Empa (Marianne Senn)
Swiss Museum of Transport, Luzern, Lucerne
September 2007, metallography and alloy composition
Nothing to report.
Analyses performed:
Metallography (unetched), Vickers hardness testing, SEM/EDS.
The metal is an aluminium alloy containing Cu, Sn, Zn and Si (Table 1). The unetched metal shows an as-cast structure consisting of the aluminium matrix with Sn (not soluble in Al) inclusions (Figs. 5 and 6), intermetallic compounds such as Al2Cu (Fig. 5, red arrows) and clusters of Al,Fe,Cu & Si phases (Fig. 5, black arrows). There are porosities in the metal (Figs. 3 and 5). The average hardness of the metal is HV1 80.
Elements |
Al | Cu | Sn | Zn | Si | Fe | O | Fe | Total |
---|---|---|---|---|---|---|---|---|---|
Metal (average) | 89 | 4.6 | 3 | 1.6 | 1 | < | 0.8 | < | 100 |
Intermetallic compounds | 45 | 55 | < | < | < | < | < | < | 100 |
Al,Fe,Si,Cu phase clusters | 58 | 11 | < | < | 7.5 | 29 | 3.4 | 29 | 109 |
Sn inclusions | < | < | 100 | < | < | < | < | < | 100 |
Table 1: Chemical composition (mass %) of the metal and inclusions (from Fig. 5). Method of analysis: SEM/EDS, Laboratory of Analytical Chemistry, Empa.
Dendritic structure with inclusions
Al
Si, Cu, Zn, Sn
Nothing to report.
No corrosion layer can be seen on the metal surface (Figs. 3 and 7). Under polarized light small white and brown particles are visible on the broken edge (D1, Fig. 8). Their analysis reveals the presence of silica particles surrounded by dirt (Table 2 and Fig. 9). The metal surface is covered by a thin oxygen bearing skin (CP1, Fig. 9).
Elements |
O | Al | Si | Cu | Total |
---|---|---|---|---|---|
Adherent particle (average of 3 similar analyses) | 55 | 0.6 | 50 | 1.1 | 106 |
Table 2: Chemical composition (mass %) of the adhering particles to the metal surface (from Fig. 7). Method of analysis: SEM/EDS, Laboratory of Analytical Chemistry, Empa.
Fig. 7: Micrograph showing the metal - “corrosion products” interface from Fig. 3 (reversed picture, detail), unetched, bright field. We observe in white the metal matrix, in dark-grey Al,Fe, Si & Cu phase and light-grey Al2Cu intermetallic compounds. The micrograph of Fig. 8 is marked by a rectangle,
Passive
None
Nothing to report.
Corrected stratigraphic representation: none.
Although not common at the beginning of the 20th, this Al-Cu-Sn-Zn-Si cast alloy was used on the Dufaux IV plane. No corrosion layer has been found on the metal surface except adherent silica-rich particles and the thin oxidised skin typical of Al alloys. The presence of these materials can be explained by the regular maintenance of the metal, probably using silicon carbide abrasive paper.
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