Question
is it safe to put iron(chaving from a brake lathe) on bermuda grass to green it up

Answer
Mike,
The yellow condition of your bermuda may be due to an alkaline soil, as well as iron deficiency.  There are balanced fertilizers for use on this condition with chelated iron.  But without a lower pH, they will not activate sufficiently to make the iron available.
As far as I know, it should be safe to apply Fe from brake honings.  I would add some elemental S (sulphur) to the mix to lower a potentially high pH.
The safe route would be to conduct a siol analysis and determine how much pH adjustment is necessary, if any.  Then, after correcting the pH, apply iron.
The iron oxide from rusty brake honings may take a while, but they should be effective.
Best of luck,
Tom