Re: Katana metals
You should never - NEVER - block anything harder than tofu with a katana - no matter what material it's made of. Deflect if need be but never block.
Many good things can come from practicing with an iaito (usually a cast blade made from a zinc/berylium alloy). The sword is cheaper than a forged katana, you are less likely to hurt yourself (or someone else) and you can learn a lot from a good iaito.
Later when you know what you are doing you can 'upgrade' to a real sword. Usually they wil run you about 9K USD and up if you want one from a certified japanese blacksmith. You can get cheaper katanas from f.eks. Paul Chen but I wouldn't recommend it for a beginner.
Just my 2 cents.