Abstract
In this work, the interaction between dislocation loop (DL) and coherent twin boundary (CTB) in a body-centered cubic (BCC) tantalum (Ta) film during nanoindentation was investigated with molecular dynamics (MD) simulation. The formation and propagation of <111> full DLs in the nanotwinned (nt) Ta film during the indentation was observed, and it was found that CTB can strongly affect the stress distribution in the Ta film, and thus change the motion and type of dislocations. There are three kinds of mechanisms for the interaction between DL and CTB in a twinned BCC Ta film: (i) dislocation absorption, (ii) dislocation desorption, and (iii) direct slip transmission. The nucleation of twin boundary dislocations and the formation of the steps in CTB were also observed during the indentation. The mechanisms presented in this work can provide atomic images for understanding the plastic deformation of BCC metals with mirror-symmetry grain boundary structures, and provide available information for the evaluation and design of high-performance nt BCC metallic thin film coatings.
Highlights
Metallic thin film coatings have attracted considerable attention due to their unique physical, mechanical and thermal properties [1,2,3], such as high strength, high hardness and high melting point, etc
Some researchers [8,9,10] performed the nanoindentation on single crystal Ta using molecular dynamics (MD) simulations, in which they found the formation of dislocation loops (DLs) and clarified the plastic deformation of Ta
There are three kinds of mechanisms for the interaction between DL and the coherent twin boundary (CTB) in the body-centered cubic (BCC) Ta film: (i) absorption of incident dislocations by the CTB, (ii) desorption of the dislocations blocked at the CTB, and (iii) direct slip transmission when incident dislocations pass through the CTB
Summary
Metallic thin film coatings have attracted considerable attention due to their unique physical, mechanical and thermal properties [1,2,3], such as high strength, high hardness and high melting point, etc. Some researchers [8,9,10] performed the nanoindentation on single crystal Ta using molecular dynamics (MD) simulations, in which they found the formation of dislocation loops (DLs) and clarified the plastic deformation of Ta. It is known that grain boundaries (GBs) may play a crucial role in the mechanical properties and plastic deformations of nanocrystalline materials.
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