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The Weld
The Steel Eyelet
The Aluminum Rim
Rolling
Rims
References: [1]: How It's Made: Aluminium Bike Wheels. Youtube. Discovery: Science Channel, 4 Dec. 2011. Web. 30 Apr. 2015 5083." [2]: Lyman, Taylor, ed. Metals Handbook. Novelyty: American Society for Metals, OH. Print. Joining Aluminum Alloys, [3]: ., [2]: Yazdipour, A. R., A. Shafie, and Jamshidi Aval. "An
Investigation of the Microstructures and Properties of Metal Inert Gas and Friction Stir Welds in Aluminum Alloy
The most common processing methods for aluminum bike
rims was researched. From the research we concluded
that the mountain biking rim was bent from a long
straight tube of extruded aluminum. Then, the rim wheel
profile tube was formed as a hollow shape using a spider
and die. Additionally, the two ends of the rim are welded
together before being heat treated [1]. The resulting
microstructure is shown above. Fine equiaxed grains are
present along with silicon, iron, and manganese
intermetallics. These impurities within the aluminum
matrix are too expensive to remove.
EDS analysis revealed Ni and Cr within the steel. Ni
stabilizes the austenite and Cr has anti-corrosive
properties. The eyelet material was likely drawn and
then formed as indicated by ghost lines parallel to the
drawing direction. The deformed δ-ferrite stringers are
present within an equiaxed austenitic stainless steel
matrix.
20mm
28mm
A vertical weld line is
present in microstructure.
There are elongated grains
along the weld line from
deformation. These flow
lines hints to some form of
butt-welding, where
solidification occurs under
external pressure. The
aluminum rim was likely
fusion-welded, due to the
presence of a liquid weld
pool [3]. It cannot be
confirmed if it was MIG or
TIG welded due to the
localized deformation at
the weld line.
David Burak and Spencer Fruend
Conclusions 1. The bulk of the rim is composed of 6XXX series aluminum. It was solution strengthened through likely Mg2Si particles. 2. The aluminum rim was extruded and then heat treated, resulting in fine equiaxed grains.
3. The ends of the aluminum rim were welded together, likely under pressure through fusion welding.
4.. The eyelet is composed of stainless steel, and was likely drawn and then formed. Ghost lines are present in the austenitic matrix
Introduction A lightweight high performance DT Swiss EX 5.1D bike rim was investigated.
The bulk aluminum alloy, the weld region of the rim, and the stainless steel
eyelet which houses the spokes were of interest. The rim was sectioned
accordingly, mounted, ground, and polished with standard metallographic
techniques. The aluminum was etched in Weck’s reagent for 12-15 seconds and
the stainless steel eyelet was electrolytically etched in 60% nitric acid for 15
seconds.
The macro photo of the
weld line shows the two
ends of the rim coming
together. The liquefied
metal solidified under
pressure during butt
welding. The solidified
region from the fusion zone
can be seen at the bottom of
the image. The excess
material on the outside of
the rim was machined off.
Weld Line Aluminum Rim
Weld Line
EDS and SEM was performed on the sample and
demonstrated alloying elements of Mg and Si, most
commonly in the form of Mg2Si micron sized particles . .
Magnesium and silicon are the major alloy additions in
6XXX series aluminum. These Mg2Si particles solution
strengthen the aluminum in the heat treated condition by
blocking dislocation motion. The Si enhances the strength
and Mg adds to the corrosive resistance of the rim [2].
2 mm
110 µm
50 µm
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