Effects of aligned graphene sheets on mechanical properties of ZK61 alloy

Lightweight magnesium (Mg) alloys suffer from their relatively low strength and limited ductility. The addition of graphene can effectively improve the strength and ductility of Mg alloys. However, the mechanism of improving ductility by graphene in Mg alloys has been generally neglected, as evidenced by a lack of studies. To reveal the mechanism, ZK61 alloys reinforced with reduced graphene oxide (rGO) are fabricated by spark plasma sintering (SPS). After compressive tests in the direction of the axial pressure in SPS (Z direction) and the direction perpendicular to the axial pressure (X/Y direction), the rGO/ZK61 composites exhibit high ductility in the Z direction. Transmission electron microscopy (TEM) reveals that some of the aligned rGO sheets are parallel to the X/Y direction. The aligned rGO sheets show a high ability to suppress deformation twinning in the Z direction and provide high strain hardening. This activates the non-basal slip system to improve ductility, thereby leading to highly uniform elongation and good ductility.