Identify what alloy of metal tool The title is more general than my particular question, in particular I bought a "allen key" and it broke after doing a lot of force with it trying to turn a hard screw.
In order to get a harder tool I need to know the material of this one. Tell me how to test if this allen key is chrome vanadium. If i should weight it, measure volume thus density, and this picture:

broken allen
The other broke like this, it deformed:

deformed allen key, because forcing

I want to be also a little educated on this topics: probably the tool is chrome vanadium but of low quality, or maybe it is extremely expensive or hard to test for me if the new tools I bought are of another material and if it's harder than the broken ones, the new ones are chrome vanadium and "stanley" (a corporation).
You can tell by the dark gray appearance that it is not vanadium chrome, but rather an alloy of hardened steel.  If it were made of vanadium chrome, it would not have broken, and it would also have a silver appearance to it.  Density may help tell if you are close, but with alloys the density does not necessarily conform to the rule of mixtures.