Processing MMC Tubes Via Friction Stir Backward Extrusion

In the present study, the feasibility of processing of MMC tubes via friction stir backward extrusion (FSBE) technique was investigated. In this regard, an aluminum alloy 1100 bar was utilized as initial raw material. In the FSBE method, the initial material is placed inside a chamber and a rotating punch is fed downward penetrating into the material softened due to the generated frictional heat. Consequently, the material is back extruded around the punch and a cylindrical tube is formed. In order to compare the results, first, a tubular specimen was produced by the FSBE method. Then, several through holes with 1.5 mm diameter were drilled by a super drill machine. These holes were filled with SS 316 powder having micrometric dimensions. The prepared specimens were processed via FSBE technique and MMC tubes were successfully produced. The distribution of powder particles was investigated by metallographic observations. Furthermore, the mechanical properties of the processed tubes were documented by Vickers hardness measurements and tensile tests. The comparison of the results demonstrates that the MMC tubes have higher strength and lower ductility. The material deformation behavior during FSBE was simulated by a coupled structural-thermal model via DEFORM finite element software.