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magnesium metallurgy 101?(4 posts)

magnesium metallurgy 101?zippi
Jul 6, 2003 4:03 PM
can someone tell me how a soft metal like magnesium be used to make a stiff, reliable bicycle frame, (pinarello dogma)? also, what is the longivity of magnesium and how stiff is it compared to al., carbon, ti, ect?
Is it softer than aluminum?Kerry Irons
Jul 6, 2003 4:40 PM
I don't know the hardness of either metal, though I'm sure you could Google it, but I'm guessing their properties are not that far apart. Mg is just a lot more flammable! Just like Al alloys, you can taylor the properties of Mg alloys, plus you can control a lot of stuff by tube design. Until you see the property profile of the tubes used in the Dogma, be careful of blanket statements. Lifetime is also dictated by the design of the frame and the quality of construction, not typically by the nature of the un-alloyed element metal.
Most metals are relatively softfiltersweep
Jul 6, 2003 7:02 PM
hence the use of alloys. Magnesium is an element- and in its pure form it isn't even very stable.
Dogma MgMycroft
Jul 7, 2003 2:13 AM
The material used in the Pinarello Dogma is, I believe AK 61 tubing which has been sourced and is exclusive to Pinarello for 2 years.

It is an alloy and not the element. Pure elemental Magnesium is highly inflammable with extremely high combustion temperatures - and reported caused a fire (where employees were killed) at Avid that stopped their manufacture of their famous SD Mag V brakes (lightest ever). You will find magnesium alloys in Time Mg Ti Impact pedals as well as most good quality front MTB suspension forks. Many previous magnesium frames (admittedly for MTBs) were sourced out of the old Iron Curtain and had reliability problems because they were brittle. Easton, for example had a hell of a job with their early batches of their Magnesium stems (Mg 60s) corroding despite being painted.

The current issue and the ones that everyone is watching is how corrosion resistant is the Dogma tubing (supposedly sent to Marzocchi [Italian suspension fork manufacturer] for special coating), and another is the weld integrity at structural joints subject to high stress.

Hope this helps.

TC