Deformation paths related to equal channel angular extrusion

Equal channel angular extrusions (ECAE) involve complex loading. The nature and the amplitude of the change of strain path for the different routes are analysed using a scalar parameter. The value of the parameter is related to the activity of the slip systems and permits to distinguish loading modes involving strain reversal, latent hardening or monotonous deformation. The strain path is a function of both the rotation of the billet before reintroduction in the inlet channel and the angle between the channels. It appears that a constant strain path is not achievable during ECA Extrusions: the dislocation glide is either reversed on previously active slip systems (route C) or promoted on latent systems (route B). Depending on the device geometry, route A corresponds either to a reversion of the glide direction or to latent hardening. The room temperature strength of an aluminium alloy for a given strain is shown to increase with the number of extrusions promoting latent hardening.