Modification of Mechanical Properties of Aluminum Alloy Rods via Friction-Extrusion Method.

Anna Wójcicka,Krzysztof Mroczka,Jerzy Morgiel

doi:10.3390/ma13225224

Abstract

The elaboration of a modified friction-extrusion method aimed at obtaining 2017A aluminum rods of gradient microstructure is described. This was achieved by cutting spiral grooves on the face of the stamp used for alloy extrusion. The experiments were carried out at a constant material feed (~10 mm/min) and a range of tool rotation speeds (80 to 315 rpm). The microstructure observations were carried out using light microscopy (LM) and both scanning and transmission electron microscopy (SEM and TEM). The mechanical properties were assessed through hardness measurements and static tensile tests. The performed investigations show that material simultaneous radial and longitudinal flow, enforced by friction of the rotating tool head and extrusion, results in the formation of two zones of very different microstructures. At the perpendicular section, the outer zone stands out from the core due to circumferential elongation of strings of particles, while in the inner zone the particles are arranged in a more uniform way. Simultaneously, the grain size of the outer zone is refined by two to four times as compared with the inner one. The transfer from the outer zone to the core area is of gradient type. The hardness of the outer zone was found to be ~10% to ~20% higher than that of the core.

Highlights

Plastic deformation (PD) of metals and alloys—realized in a number of ways—can be very effective in controlling the shape, microstructure and mechanical properties of the final products.Some limitations of this approach were found to be a low number of easy crystallographic slip systems in some metallic materials, or their unfavorable shape, such as in the case of aluminum scrap
The preliminary friction extrusion tests showed that only those performed at higher rotation
Pressing the punch with a spiral groove cut at the outside of its face and a hole at center allows the obtainment of rods, whose outer zone is the subject of a much higher level of plastic the center allows the obtainment of rods, whose outer zone is the subject of a much higher level of deformation than that of the core

Summary

Introduction

Plastic deformation (PD) of metals and alloys—realized in a number of ways—can be very effective in controlling the shape, microstructure and mechanical properties of the final products Some limitations of this approach were found to be a low number of easy crystallographic slip systems in some metallic materials, or their unfavorable shape, such as in the case of aluminum scrap. The approach borrowed from friction steer welding (FSW) [6,7,8] is especially useful in such applications as it is capable of locally varied strong microstructure refinement. Previous experiments used this idea in such a way that spiral grooves covered all of the face of an extrusion die [4,5]. The ease of joining E and FS processes offers the possibility of experimenting with them, especially as concerns the parts controlling

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