Stabilization of the open-die forging process of TiAl alloys by using a close-loop control in the finite element simulation in case of unexpected disturbances

High-strength Titanium Aluminide (TiAl) alloys hold great potential for future applications in lightweight turbine blades. Their success depends on reliably achieving a consistent transformation from the initial cast microstructure to a globular target microstructure throughout all critical areas of the blade. The exclusive use of a multi-stage closed-die forging process means that TiAl alloys cannot be reliably formed into turbine blades. The process chain must therefore be extended by a multi-stroke open-die forging process in order to integrate further degrees of freedom into the process. During the open-die forging of TiAl alloys, however, unexpected process disturbances often occur, e.g. in the form of a fluctuation in temperature or forming speed, which has an unwanted effect on the microstructure. For the simulations within the present work, a finite element model of the considered process is included, which is extended by a corresponding material model to describe the globularization state of the material and a closedloop control. The exponentially damping controller developed in the research project is intended to regulate disturbance variables as quickly as possible to achieve a minimum deviation from the target microstructure state. The function of the controller is simulatively tested, discussed and evaluated as part of the work.