I assume that the toggle that failed was because of fatigue as a result of long use and many miles. Certainly there was no shock loading involved. The new stainless one is certainly pretty but I am sure it will not stay that way for long. My wife has her PhD in metals and corrosion and we saw some titanium fittings in a store here. She thinks that is the material but the price is ridiculous.
i think that Rich may have it nailed that bronze production has just become too problematic from the environmental and cost perspective. When my boat was built it had a lot of bronze fittings, not so many anymore.
Bronze (like any copper alloy) can 'fatigue' in the sense of work hardening/embrittlement, but good silicon bronze is fairly resistant to fatigue if kept w'in a working limit of, say, 25% breaking strength. I would guess (guess!) that you experienced enuf transient dynamic loads during your recent passages to push the fitting past its limits frequently enuf to cause work hardening. There is also the possibility of galvanic corrosion, tho that's an unlikely place for it.
Stainless also work hardens -- but that's mostly during machining, at the micron-thick cutting interface. In operation, your steel alloys are highly resistant to cold hardening. That's one of the glories of steel. They can also be hot-worked w/out totally messing up their properties, which cannot be said of bronze or aluminum.
Bronze hasn't got so expensive because of environmental concerns -- you can bet the Russians, Chinese, and Chileans aren't exaclty following the Clean Water Act -- but rather because the commodity price of the base metal (copper) tripled around 2004. This was during the peak of the US housing boom and more importantly China's & the UAE's city-building boom, which continues today, albeit slowing. As someone who was wiring a new house and shop at that time, I can tell you what it did to the cost of Romex.
Also, bronze has become very much a specialty or niche product, with fewer smelters or founderies working it. The price is high because it is no longer a common industrial metal, except for certain military or chemical-handling operations where price is no object.
Titanium is an amazing metal with some issues when used for rigging hardware. For straight chainplates, there is perhaps no better material. Bolts and forged fittings, no problem. But there have been a number of documented failures of cold-worked parts, notably tangs and chainplates bent in vices and dies. The alloys seem to exhibit acute work-hardening and embrittlement at the bending angle. Most recent example I know of was a failed Ti mast tang on the cruising cat
Ceilydh.
Ceilydh Set Sail: Some days are like this
Not sure I would trust a random cold-formed toggle made of Ti. It has to be done just right: speed of bend, not bending back, elevating temperature before bending, heat treating afterwards. Cold-working or cold-forging Ti increases its strength, but this benefit comes at the expense of ductility & possible fracture unless the metal is later annealed to relieve stress. It's a tricky metal that requires skilled & knowledgeable people working it. If you just have Charlie bending your tang or toggle in his bench vice w/ a pair of locking pliers, stainless is a much more forgiving material.
It's possible Stumble (of Allied Ti) can set you up with a proper forged or milled or shaped titanium toggle.
http://www.alliedtitanium.com/vupdc_Results.php?S_UDescription=toggle&x=0&y=0
