Yes, I've made swords. But it was about 42 years ago. . . and they just had to produce a suitable "CLANG!" when struck together, so the nature of the steel was of little importance. They were for my college drama department. They needed about 40. I cut them out of 1 1/4" x 3/16" x 36" steel bar stock, added welded on 1/2" x 6" x 1/8" cross guard to each side 6" from the bottom, added a weded on 1 1/4" round button pommel, glued on wooden grips, wrapped that with black duct tape, ground the end to a dull point — voilà! Fairly safe stage Swords with suitable "CLANG!" It took me about a week to turn out 40 of them. We bought some fancier ones for the principal actors.
I studied a lot about the physics and chemistry of metals in college. But that was also 40 years ago and mostly theoretical. Now I work for an implant dentist who was an aerospace engineer. He is very much into materials science and knows quite a bit about these liquid metals. He developed many of the modern techniques used in dental implantology and is always looking for lighter, stronger cartable metals for such uses.
Getting back to swords, and sword making, I've also collected edged weaponry and studied their manufacture and know quite a bit about steel and the trade offs between strength, spring, hardness, the ability to hold an edge, etc. Read about the construction of Japanese swords sometimes and the folding of the metal in the various layers that goes into a katana and the qualities each part of the interior and exterior metals of the sword provides to the overall finished product. Created through empirical trial and error over centuries of sword making, the results of fine Samurai blade technology still challenge the efforts of modern metallurgy to duplicate.
Like the challenge of the pyramids, the issue for modern technology is not one of possibility but instead practicality. Modern technology would not attack the problem in the same way as the Samurai sword makers did. Yet they attacked the problem in a novel way that made the best use of the willingness to expend time and resources available to create a superior product.
Steels are capable of incredible properties, as you pointed out in the issue of precipitation hardening of the 17-4 Stainless. Ultimately, this all comes down to structure. Steel is a conglomerate of soft iron and hard iron carbide in some form. Stainless Steels have enough alloy that they may still transition into ferrite or not and stay austinitic, yet the strength of this material still depends on the grain structure, and the placement of the carbides. Trace elements like vanadium increase the hardenability of the steel by stabilizing the carbides at higher temperatures. Ultimately strength and ductility typically go in opposite directions but the fineness of the grain and carbide precipitates increases the ductility. Steel achieves its strength from the hard bits and its ductility from the soft. Like butter filled with sand becomes hard but can be shattered with a small blow. The ferrite stretches and holds the structure together like rubber bands and yields when the forces become too high.
When a metal is quenched so fast that the hard brittle structure called martinsite cannot form from the austinite, it transitions to a very fine but brittle structure called bainite. Heat treated properly, this structure yields the finest structure of ferrite and cementite and thus the best properties possible for steel. However, it is difficult to quench plain carbon steel this fast and the hardening alloys such as vanadium, chromium, and others make this possible as they are increased and at some point make this possible even in a relatively slow oil quench.
The samurai sword masters achieve this very same sort of fine grain with their folding work, and overlay this with a very highly directional structure that provides the equivalent of modern composite structures in that the impurities and such are turned into a structural element that provides additional stability to the blade in its intended axis of loading by aligning them parallel with the flat surface of the blade. The risk being that the blade if the laminations are not broken up sufficiently can be vulnerable to splitting. Yet for most blows, these flaws are not stressed appreciably and instead the full strength of the material is available.
Engineers who deal with steel professional start seeing it like wood. Thinking of grain and the failings of grain like it fails in wood. Materials such as tools and highly worked and heat treated steel items do not suffer this effect as much because the grain size and configuration is more controlled. Quenching to martinsite or bainite prevents grain formation and thus the structures formed are very very fine after heat treatment releases the enormous internal stresses that the transformation causes and precipitates the carbides into a fine matrix of cementite among very small grains of ferrite.
Anyway, the cost of processing is the main deterrent to folks attempting to replicate the swords of the old masters. Other than proving a point, there isn't much demand for genuine swords of these characteristics. As you say, most swords now are good enough if they just "clang" well. LOL.