A new wavy cross-sectional torsion extrusion method with an application to improve the mechanical properties of an aluminum matrix composite

Abstract

Torsion extrusion (TE) as a severe plastic deformation (SPD) method has shown promise in effectively improving the mechanical properties of metal matrix composites (MMCs) by means of extreme shear strain. However, the circumferential sliding between the rotating die and the material seriously degrades the shear effects during TE processing. In order to address this challenge, a modified torsion extrusion method, namely wavy cross-sectional TE (W-TE), was proposed to enhance the shear effect. The method applied a rotating die consisting of a deformation cavity followed by a bearing segment with a wavy cross-section. The material is extruded through the rotating die, and the wavy cross-section holds the deformed billet to rotate with the rotating die, so that the relative sliding is prevented. The method was applied to an in-situ TiB2 particle reinforced 2026 Al composite for dispersing the reinforcing particles and refining the microstructures. Numerical simulations indicated that the W-TE processed material undertook larger torsion deformation than the ones processed by the conventional TE, so the shear effect was enhanced. Experiments showed that, compared with the conventional TE, W-TE can efficiently disperse the reinforced particles and refine the microstructure of the extruded materials. Mechanical tests demonstrated that the samples processed by W-TE exhibits a simultaneously increase in the strength and ductility. Furthermore, with the aid of the enhanced shear effect, the extrusion force of W-TE was reduced greatly compared with conventional extrusion or other TEs, thus making the proposed W-TE an efficient way for improving mechanical properties of metal matrix composites.