Molecular dynamics simulation of dislocation network formation and tensile properties of graphene/TiAl-layered composites

Abstract

Alternating stacked graphene/TiAl (Gr/TiAl) composites exhibit excellent mechanical properties because of their high strength, high Young's modulus, and the two-dimensional atomic structure of graphene. Herein, a molecular dynamics approach was used to investigate the uniaxial tensile properties of Gr/TiAl composites after rapid solidification. The results of the simulation show that after rapid solidification, the composites were more crystallizable and were accompanied predominantly by a Shockley type dislocation network, with large periodic hexagonal superlattices (also known as the Moiré pattern) of ∼12.519 and 10.092 Å. Increasing the tensile load activates dislocation emission, which enhances the interaction between dislocations and numerous dislocations, forming a large number of entangled dislocation nodes. This increases resistance to the motion of the remaining dislocations and creating a strengthening effect. The spacing between graphene layers has a substantial effect on the tensile strength and Young's modulus of the Gr/TiAl composites. The composites with smaller layer spacing exhibited better performance than those with larger layer spacing. Because of the dislocation-blocking mechanism between Gr/TiAl interfaces, graphene blocks the propagation of dislocations and takes up most of the load, yielding composites with high Young's modulus, tensile strength, and breaking strain than pure TiAl.