Aerospace Material Specification 4773 is silver alloy BAg-18 in welding wire, welding rod, powder, and paste. Typically used for joining ferrous metals requiring high joint strength at moderate temperatures. Particularly useful for brazing with hydrogen or inert atmosphere.
Ag: 60% | Cu: 30% | Sn: 10%
Further reading: BAg-21 brazing filler metal.
Further reading: WT 92.5 AMS 4767 silver alloy.