Simultaneously enhancing strength and ductility in graphene nanoplatelets reinforced titanium (GNPs/Ti) composites through a novel three-dimensional interface design

The interface debonding caused by mismatched thermal expansion is a key issue in graphene nanoplatelets/Ti matrix composites (GNPs/TiMCs), which significantly decreases the composites' mechanical properties. In this study, GNPs/Ti composites were fabricated by spark plasma sintering (SPS) followed by heat treatment (HT) routes. A novel strategy that strengthening the GNPs-Ti interface bonding via tailored three-dimensional (3D) interface configuration was proposed for the first time. Characters of interface evolution (before and after HT processes) were discussed detailedly in conjunction with the in-situ formed TiB whiskers (TiBw). The interfacial microstructure displayed that GNPs was used as template for the heteroepitaxial growth of TiBw, then TiBw connected the TiC layer and the adjacent Ti matrix. Tensile tests showed that GNPs-(TiBw)/Ti composites exhibited excellent strength-plasticity compatibility as compared to GNPs/Ti. Ex-situ compression tests of micro-pillars fabricated from the bulk composites revealed that the 3D interface configuration in GNPs-(TiBw)/Ti possessed significantly higher strain accommodation and strain-hardening ability during deformation. This study highlights the importance of interface optimization, which is helpful for developing the interfacial engineering and achieving good properties in GNPs/TiMCs.