I have a titanium wedding ring, machined by an aerospace shop outside of Seattle from scrap left over from a NOAA ultra-deep submersible.

Ti tends to propagate cracks more easily that Fe alloys, so after some experimentation by F1 teams for suspension parts, it was rapidly phased out. However, its stability at high temperatures makes it pretty popular in high-heat applications like rocket or jet engine parts. We used to see pieces of thin-walled Ti tubing at Boeing's surplus store Kent, WA that looked about the right size for exhaust systems but when we went looking for advice about how to fabricate it, we got shut down. Assuming you can get the parts built, it seems like it would be awesome. It also doesn't rot like steel.

K