Interchanging blades

I've purchased a very well used scythe last year and have been  using it around our homestead for various cutting of grasses weeds and very small brush. I read in the forum that there is a brush blade available and I'm wondering if all scythes can have interchangeable blades or just some. Also, I've been using the blade that was on the scythe when I bought it for small brush and it seems to do ok with it - but am I going to wreck the blade by using it on brush ? I have no idea how old the scythe is but my best guess is 20 or 30 years old. Any thoughts most appreciated.

Hard to know what to tell you without knowing more about the scythe. Are you able to post pictures?

In general: you can switch out blades and the more robust the material to be cut, the more robust the blade should be to avoid damage.