Effects of Welding Chamber Height on Properties of Porthole Die Extrudates Made of 0.5 Wt.% Gnps/Al Composite

Abstract

In this study, porthole die extrusion was performed on a 0.5 wt.% graphene-nanoplatelet-reinforced aluminium matrix composite by using welding chambers having heights of 10, 15, and 20 mm. The effects of the welding chamber height on the microstructure and mechanical properties of the composite in the welding zone were studied. The results showed that the mechanical properties of the composite along the 90° direction improved with an increasing welding chamber height. When the welding chamber height was 20 mm, the comprehensive mechanical properties of the composite along the extrusion direction and the vertical direction were the best. This was mainly because a higher hydrostatic pressure and shear force in the welding chamber with the height of 20 mm increased the recrystallisation degree of the composite, resulting in smaller sizes and an even distribution of the graphene and alumina nanoparticles inside the grain, which played positive role in hindering the dislocation slip. Further, the interface between graphene and the matrix was also enhanced. The presence of graphene hindered the closure of micro-holes in the weld, and an increase in the welding chamber height effectively reduced the size of micro-holes, thereby improving the welding quality.

Keywords: 0.5 wt.% GNPs/Al composite, porthole die extrusion, welding chamber height, welding quality, mechanical properties