I asked my materials science proffesor if forging a cast part (inside a mold to prevent shape change) can increase it's strength to that of a forged part. She told me to find out myself and tell the group next lesson. I googled for a bit on post casting treatment but haven't got a clear answer to my question. Is it possible?
Generally , no. That is more or less cold working , but the die prevents much strain , so very limited strain hardening / cold work. That could be called a "coining" operation. A special case could be a poor casting with gas porosity , shrinkage cracks or hot tears ; wherein the forging partially remedies some of these defects.