Originally Posted by HillRider

Yes, I think you are correct that Ti has been used but not Al for skewer shafts.

Also, yes, Ti shafts and an external cams can, theoretically, apply the same force as a steel shaft and internal cam but nearly no one will ever use that much effort to close them. There is a reason frames with horizontal dropouts and/or disc brake forks using qr hubs should always use internal cam steel skewers. We have had numerous threads here reporting slipping rear wheels and disc brake misalignment that were cured by changing the skewer to a steel internal cam type.