Dynamic materials Modelling and finite element simulation of titanium alloy turbine disc forging

Titanium alloy turbine discs for aeroengines are normally produced by forging to near net shape at high temperature followed by machining. Since titanium alloys exhibit limited workability and the microstructural development during forging is highly sensitive to the processing temperature and strain rate, the selection of the processing conditions becomes very important. In this study, a processing map for Ti alloy 685 is developed using dynamic materials modelling (DMM), which suggests good workability in the α–β phase field at 960°C and at strain rates less than 10–2 s–1. In addition, a large deformation finite element analysis (FEA) of isothermal disc forging is carried out, to design the die profile that renders streamlined flow during forging. The computed distribution of strain and strain rate in the deforming billet integrated with the results of DMM aids in designing the forging scheme to achieve uniform microstructure in the final component. In this context, the importance of upsetting prior to forging is also discussed. The paper includes experimental validation of the FEA–DMM integrated approach