During isothermal forging, the dies are heated to the same temperature as the forged part. This allows shaping at any rate without the forged part cooling down. This process sometimes also takes place in an inert gas or vacuum. This complex technical procedure keeps the shaping forces low and ensures an even, fine-grain microstructure with the resulting outstanding performance characteristics.
However, it calls for a lot of know-how and special machinery. Materials that cannot be forged conventionally such as titanium aluminides or powder metals can now be shaped by this process. Special tool systems of nickel-based or molybdenum materials are used for this purpose. Leistritz has been using this method for many years to forge aircraft engine disks of titanium and nickel alloys, and more recently to forge turbine blades of titanium aluminides, too.