Classiccomponents–Duralumin
It is argued by some that knowledge of wrought aluminium alloys is the aero industry’s preserve. A viewpoint – but there are many examples of their use in motorcycle engineering including duralumin, now in the International Alloy Designation Scheme’s 2000
Cast aluminium is an example of a material which can be melted, often by furnace, poured into a mould to shape it, then allowed to cool and set into a solid form. Wrought metals including aluminium and aluminium alloys are metals which have been worked in the solid form into the desired shape, such as plate, rod, tube, block etc.
To produce wrought aluminium alloy, smelt pure aluminium and the specific alloying elements and cast into billets, slabs or other. Then shape into plates, rods, angles, girders and much more, using a range of processes, including extruding, forging and rolling.
Wrought aluminium alloys generally have lower percentages of alloying elements than cast aluminium alloys, which typically have a lower tensile strength compared with wrought materials, often due to the problems of eliminating casting defects when casting in moulds.
Naming scheme
There have been and are a number of naming schemes with the most accepted being the International Alloy Designation System (IADS), which gives each alloy a four digit code.
Identifies major alloying elements
0 = no variation of alloying elements indicated by first digit
1 = 9 identifying variations of alloying elements indicated by first digit Identifies the specific alloy
Example: duralumin
Duralumin (aka duraluminium, duraluminum, duralum, duralium, dural etc) is a trade name derived from DURAble aLUMINium. This name is seldom used today except by ageing hooligans like me who bought proprietary Duralumin engine plates and the like when attempting to build specials. It hardens with age and is in the IADS 2000 series, a series of aluminium/copper alloys, and, apart for its use for motorcycles, was the main material for early aero airframes. It is liable to stress cracks/fractures. Superseded by aluminium alloys in the 7000 series.
German metallurgist Alfred Wilm developed Duralumin c1903 and it was first commercially used in the aero industry for the Junkers J3, and later the framework structures of airships. It became favoured for cycle parts and frame sets in the early 1930s. At the same time, it was used for prototype and limited production motorcycle frames and then for motorcycle parts including engine/gearbox plates and aluminium alloy rivets for box section motorcycle frames.
Other aluminium alloys in the IADS 2000 series are often also known as Duralumin which serves as our example of the huge number of aluminium alloys available.
IADS series
1000 series, pure aluminium or with less than 1% alloying elements, work hardens.
2000 series, alloying element is copper with others to a lesser degree, precipitation hardens.
3000 series, alloyed with manganese, work hardens.
4000 series, (aka silumin) alloyed with silicon, (casting siliconaluminium alloys aren’t included in this group).
5000 series, alloyed with magnesium and often manganese, resists corrosion well and group members have highest strength of nonheat treated aluminium alloys.
6000 series alloyed with magnesium and silicon, machines and welds well, can be precipitation hardened.
7000 series, alloyed with zinc and often copper, if precipitation hardened its has the most strength of all aluminium alloys.
8000 series, alloyed with others elements such as lithium.