I find it interesting that there is a shiny area on the tear, this material will not do this under normal circumstances, is that really like that or is it just the pic? If there is a void or crack, it could be very tiny and hard to see. I would imagine that this would be close to the leading edge of the blade, as the tear propagates back to the hub, the centrifugal force would make this section rotate as it comes out, the leading edge of the blade would hit the bell mouth forcing the broken section out through the back of the compressor, as you can see in the pic it has the bent back portions on the side . What does the bell mouth and diffusers look like? I imagine there done.
That is a very old style compressor is this what come with a Ram?