Microstructure and Mechanical Characterization of Aluminum Seamless Tubes Produced by Friction Stir Back Extrusion

Abstract

Friction stir back extrusion (FSBE) is emerging as a novel method to produce high strength fine grained metallic tubes. The objective of the present work is to produce aluminum seamless tubes from solid cylindrical bars using FSBE and to report the microstructure and mechanical characterization. A die, tool and fixture were designed to carry out FSBE. A conventional friction stir welding machine was utilized for FSBE. A cylindrical bar of aluminum alloy AA6061-T6 was kept inside the hole in the die and extruded by plunging the rotating tool. The microstructure of the produced tube was studied using optical microscopy. The microstructure was found to be homogeneous along the tube. The microhardness and compressive strength of the tube have been presented in this paper. The results indicated that the FSBE process was capable of producing sound aluminum seamless tubes.