Originally Posted by
FBinNY
Ductile failure isn't an inherrent property of either material, its a sign of good engineering. Whether working with steel, aluminum, or titanium, parts can be designed and materials spec'ed with consideration to the mode of failure. Ductile failure over time, even a fairly short time, is preferable to sudden unannounced catastrophic failure, and good designers build that in whenever possible.
Where it isn't built in, knowledgeable consumers can select parts with that in mind. It's one reason that, despite lighter stronger alloys being used today, I still ride with 2000 series aluminum handlebars.
While good engineering may be necessary to have ductile vs. brittle failure, you also need a ductile material. Most steels allow ductile failure and most aluminums do not... not enough elongation or deformation can happen before breaking.
Anyhoo, failure is failure is failure. After a frame has failed it should no longer be ridden. I am constantly frustrated by advice on here by people who do not undestand what 'failure' really is - there are many reccomendations to continue riding bikes with mangled steel frame because they think there will be some further 'warning' before failure... well guess what? The bending is the 'warning' and the next step is snapping in half and leaving your face spread down the pavement.
I am happy to report that noone in this thread gave the OP this dangerous advice, and when his frame finally finishes snapping in half he will have noone but himself to blame and help him get around in his wheelchair.