Abstract: A friction-stir mandrel includes a textured end portion integral with a body portion. The textured end portion is configured to friction-stir process a starting material forced across the textured end portion and through a die in a plasticized state to form a pipe. A pipe can be formed by forcing a starting material across a textured end of the mandrel and through a die in a plasticized state, so that the textured end of the mandrel breaks up existing grains of the starting material. The pipe is formed from material that is forced through the die. The friction-stir mandrel can be used with porthole die friction-stir extrusion, seamless tube friction-stir extrusion, and tube friction-stir drawing processes to provide tubing in which the grains are broken up by the textured portion of the friction-stir mandrel. The textured portion can include features, such as threads, ridges, studs, protrusions, and the like.