Interface evolution and superior tensile properties of multi-layer graphene reinforced pure Ti matrix composite

The interfacial structure and mechanical properties of multi-layer graphene (MLG)/pure Ti composites produced by spark plasma sintering (SPS) and subsequent hot-rolling (HR) have been investigated. The hot-rolling temperature has been set at 823 K, 1023 K and 1223 K for composites to obtain various interfacial characteristics and microstructures. (Transmission electron microscopy) TEM observations reveal three types of temperature-dependent interface: Ti carbide nucleation, Ti carbide particles growth and Ti carbide layer formation. Moreover, there exists special crystallographic orientation relation: (1¯01)_TiC//(112¯0)_Ti and (0001)_MLG//(020)_TiC. Tensile test shows the MLG/Ti composite owns outstanding mechanical property. Specially, the 0.2 wt%MLG/Ti exhibits tensile strength of 1050 MPa, nearly two times higher than that of monolithic pure Ti. The relation between interfacial stress and strengthening efficiency has been investigated by using revised shear-lag mode in order to reveal the relation between interfacial microstructure and macro-mechanics. Results show that interfacial Ti carbides on partially reacted MLG led to the great improvement of interfacial strength and consequent enhancement of composites strength. When the HR temperature increased to 1023 K and 1223 K, the volume fraction of Ti carbides was 2.5 and 12.3 times higher than MLG. Ti carbide layer play a key role in further improvement of the tensile property.