Microstructure and strain in protrusions formed during severe plastic deformation of aluminum

•Protrusions occurring during severe plastic deformation of aluminum are characterized.•Strain is estimated in the protrusions analytically and a value of about 5.0 is found.•The same plastic strain is obtained using the disorientation distribution functions.•The protrusions present shear textures in twist extrusion.

The protrusions formed during twist extrusion of commercially pure aluminum were characterized in terms of microstructure, texture, strain and Vickers-hardness. Ultra-fine-grained structure was found with grain sizes down to 610 nm. The texture was identified as a shear texture with oblique shear plane with respect to the plane of the protrusion. The amount of strain was estimated theoretically and was also obtained by comparing the disorientation distribution in the protrusion with that observed in high pressure tube twisting.