Interface microstructure and strengthening mechanisms of multilayer graphene reinforced titanium alloy matrix nanocomposites with network architectures

Discontinuously reinforced 3D network structured Ti6Al4V (TC4) matrix composites with multilayer graphene (MLG) were fabricated via 3D dynamic mixing and spark plasma sintering (SPS) at high pressures (250-500 MPa). The interface microstructure, mechanical properties and strengthening mechanisms were systematically studied with various MLG contents. Experimental results exhibited that MLG can be relative uniformly dispersed onto the surface of TC4 powders by the 3D dynamic mixing method, SPS parameter of 700 degrees C-500 MPa caused weak interface bonding between MLG and Ti matrix, and 900 degrees C-250 MPa was determined as the optimal sintering condition. Appropriate ratio of in-situ generated TiC phase with approximately 30 vol% retained MLG at the interface was beneficial to the interface bonding. The compressive strength of the composites was remarkably enhanced with excellent compressive ductility. Superior mechanical properties with the highest strengthening efficiency (65.5%) and tensile strength, acceptable tensile ductility (9.0%) and higher Vickers microhardness were achieved in the 0.15 wt% MLG composites due to its better interface microstructure. The network interface strengthening mechanism by the TiC phase and residue MLG is proposed to be the dominant mechanism with a few contributions from C solid solution and fine-grain strengthening. (c) 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).