Microstructure and mechanical properties of AA6063 aluminum alloy wire fabricated by friction stir back extrusion (FSBE) process

Abstract

In the present work, the friction stir back extrusion (FSBE) process was used as a novel method for the fabrication of AA6063 aluminum alloy wire. Scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), tensile and hardness tests were performed. The FSBE via the rotational speed of 475 r/min resulted in fine equiaxed grains, and the mean grain size decreased from 179.0 µm to 15.5 µm due to the occurrence of dynamic recrystallization (DRX). Heat generated by the FSBE changed the size and volume fraction of the Mg2Si precipitated particles. The minimum particle size and maximum volume fraction obtained in the sample were processed by rotational speeds of 475 and 600 r/min, respectively. The 475-r/min sample had the maximum hardness value due to having the lowest grain size (i.e., 15.5 µm) and the presence of many fine Mg2Si precipitates in the aluminum matrix. With increasing rotational speed up to 600 r/min, the hardness decreased, owing to the growth of both grains and precipitates. The FSBE process with a rotational speed of 475 r/min increased the tensile strength (from 150 to 209 MPa) and ductility (from 21.0% to 30.2%) simultaneously.