Nowadays there are so many different high-tech materials, so I wonder if there is a suitable material for bicycle locks that would be much less heavy than hardened steel. If there isn't one, can somebody explain from the perspective of materials science why?
The only non-steel material used in locks that I could find is Kevlar, but mostly just as a coating around steel, and from various reviews I don't get the impression that they are better or lighter than ordinary steel ones. My understanding is that kevlar has good tensile strength (so gun bullets can't tear kevlar fabric) but it doesn't resist being sawn or cut. Carbon fibres would presumably have similar issues, it's fairly easy to damage carbon frames if you compress them so a potential carbon fibre lock wouldn't resist bolt cutters.
So are there any light materials that would have the correct properties for a bike lock? And if not, why not?