there is a very good chance that the replica sword is made from a relatively cheap stainless steel with uniform hardness through the blade. While the excerpt below is about cheap replica katanas it can apply to any such replica blade:

https://en.wikipedia.org/wiki/Japanese_swordsmithing

"Most cheap reproductions are made from inexpensive stainless steels such as 440A (often just termed "440").[45] With a normal Rockwell hardness of 56 and up to 60, stainless steel is much harder than the back of a differentially hardened katana (HR50), and is therefore much more prone to breaking, especially when used to make long blades. Stainless steel is also much softer at the edge (a traditional katana is usually more than HR60 at the edge)."

So, i'd not risk using such replica sword against a real world sword :) On the other side one can imagine how a modern sword can be made - say carbon fiber core inside titanium monocrystal envelope with fused, like laser sintered, ceramic/nano-diamond skin and edge. And resorting to cold weapons may be a reasonable alternative to guns in the future conflicts inside space stations and planetary bases.