On the modelling of the interaction of materials softening and ductile damage during hot working of Alloy 80A

Ductile fracture at high temperatures was investigated by means of continuum damage mechanics. An enhanced model of the effective stresses considering crack closure effects by splitting the Cauchy stress tensor into a compressive and tensile part is combined with a damage evolution law that has been derived from the potential of dissipation and depends on the damage strain energy release rate. Additionally, a semi-empirical grain structure model had been coupled to describe the materials softening by dynamic recrystallisation. It can be demonstrated that with the onset of recrystallisation the accumulated deformation, i.e. the effective plastic strain, is reduced by recrystallisation and hence the initiation of damage is retarded. EBSD analyses of hot deformed samples were performed in order to validate the model and to investigate the interaction of crack initiation as well as of crack progress with dynamic recrystallisation.