Originally Posted by
cyccommute
That has not been my experience with any aluminum frame or part failure. I've broken two aluminum frames and many aluminum wheels. None of them "fractured catastrophically". If you think about the material it's fairly easy to see that aluminum is unlikely to fail by "shattering" as well. Aluminum is soft and not brittle at all. It generally tears rather than experiences fracture. Aluminum also makes a lot of creaking noise after it cracks just like rseeker's bike did. I've often found that my bike "creaking" is due to some broken part that I just failed to understand was broken.
The aluminum alloys used for bike frames and rims are by their composition and heat treatment chosen to be strong at the sacrifice of ductility. My experience is that aluminum does fail rather suddenly and, if the OP is already seeing crack, they will propagate rather quickly.