Aluminium Design and Construction John Dwight

The first digit in the number indicates the alloy series, which depends
on the main alloying ingredients in the same way as for wrought alloys
(Table 4.1). Thus the AC.4xxxx series covers alloys containing just Si, and
the AC.5xxxx those with substantial Mg. Unlike wrought, the European
numbers for casting alloys do not tally with the American ones.
The symbol or symbols after the hyphen have the same basic meanings
as for wrought material:
F ‘as-manufactured’, i.e. as cast;
T4 solution treated after casting and naturally aged;
T6 solution treated and artificially aged.
4.5.2 Three useful casting alloys
A wide range of casting alloys exists, generally different from those used
for wrought products. Table 4.7 provides data for three selected alloys,
which should form part of a designer’s repertoire. The values quoted in
the table are minimum strengths to be achieved by separately cast tensile
specimens. They do not accurately represent the metal in the actual casting,
the properties of which are unlikely to be uniform. Alternative strength
values are given, depending on whether a sand mould is used or a
permanent one (chill cast), the chill-cast strength being always higher.
AC.44100
This is a non-heat-treatable alloy, available in the as-cast F condition. It
is the most popular casting alloy in aluminium, because of its exceptional
fluidity. It is suitable for intricate shapes and can cope with thicknesses
down to about 2.5 mm. At the other end of the scale, it can be used for
very large castings, up to 3000 kg in sand and 200 kg in permanent
mould. It has good corrosion resistance and is successfully employed in
‘on-deck’ marine applications.
Table 4.7 Three selected casting alloys
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