Molecular dynamics study on mechanical behaviors of Ti/Ni nanolaminate with a pre-existing void

Abstract

Metallic nanolaminated materials possess excellent mechanical properties due to their unique modulation structures and interfacial properties. However, how microdefects affect their mechanical properties is still uncertain. To evaluate the influences of void location (in the crystalline layer and the Ti/Ni interface), void diameter (d) and thickness of the intermediate layer (h) on overall tensile behaviors, various types of defective Ti/Ni nanolaminates with pre-existing void are established by the molecular dynamics method in this work. The results indicate that the strength and plastic deformation mechanisms are strongly dependent on those determinants. Yield stresses of Ti/Ni nanolaminates decrease distinctly with increasing void diameter, while peak stresses with a void in the crystalline layer decrease with increasing d/h. Different void locations lead eventually to disparate initial plastic deformation carriers around the void, and various evolutions in the microstructure of the defective Ti/Ni nanolaminates. The Ti/Ni interface plays a significant role in the tensile process. The semi-coherent interface impedes new grains and lattice dislocations from passing across the interface, while the incoherent interface facilitates dislocations generating and sliding along the interface, and absorbs the dislocations moving to the interface. The results also indicate that the strain rate significantly affects the evolution of the microstructure and the tensile properties of defective Ti/Ni nanolaminates.

Keywords

• Defective Ti/Ni nanolaminate
• Pre-existing void
• Interface
• Tensile behaviors
• Molecular dynamics