In the present study, a thermomechanical simulator (Gleeble 3500) was used to represent the solid–state bonding of aluminium in hollow dies during the extrusion of AA7020 alloy. The variations in strain, strain rate, temperature and pressure reflected those typically encountered during extrusion. The results showed that to form a good bond, strain was the most influential parameter, along with the time of deformation (bonding time). Temperature and pressure were found to be less influential within the parameter ranges investigated. On the basis of the results obtained, the ‘stretching’ of the interface has been proposed to be a critical parameter to quantify the solid–state bonding phenomenon.