Be very aware when machining titanium alloys that it will burn, and can be ignited even in a solid state. It is the only material that will burn in a pure nitrogen atmosphere. In the airplane plants, they keep buckets of a black sand close at hand anywhere that TI is being worked, just in case it ignites. I forget exactly what this substance is, but it is the only thing that will smother and extinguish at titanium fire. Water, dry chemical, Halon, etc will not put it out.
I only saw it happen once. A new guy was trying to drill a hole, not knowing what he was doing. He was almost through when the bit dulled. Instead of getting a new bit, he spun up the drill motor and pushed harder. Before he could be stopped, sparks and then a blinding white glare. The guy next to him covered the area with black sand and put it out. Almost cost several million dollars. New guy got some extra training.