Hello,  My question is regarding GTAW welding of Grade 9 Titanium seamless tubing .039"-.045" wall thickness.  I've read and heard conflicting recommendations on the proper alloy filler rod to use when welding Gr.9.
I've read in a few places to use Gr.9/Gr.9ELI. But another person who welds this material has told me to use Gr.5, a 6-4 alloy.  He explained to me that when the 3/2.5 titanium cools from a molten state the grain structure changes and loses strength, therefore he recommends the stronger Gr.5 alloy filler.  Are both these OK or is one of these improper?
Thank you.