Investigation of Interaction between Dislocation Loop and Coherent Twin Boundary in BCC Ta Film during Nanoindentation

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.

Temperature and Pressure Dependences of the Elastic Properties of Tantalum Single Crystals Under <100> Tensile Loading: A Molecular Dynamics Study

“…Recently, a great deal of effort both in experimental [ 2 , 5 – 7 ] and theoretical [ 8 – 14 ] fields have been put into the high-pressure and high temperature properties of Ta. Dewaele et al [ 5 ] studied the effects of pressure on the yield strength of Ta in a diamond-anvil cell (DAC) up to 93 GPa, and the DAC experiments also presented the BCC structure remained stable up to 135 GPa [ 2 ].…”

Inapparent Strengthening Effect of Twin Interface in Cu/Pd Multilayered Films with a Large Lattice Mismatch

“…According to lattice mismatch parameter on an interface, δ = (a A − a B )/a A , the multilayered films consisting of the constituents (A and B) with the same lattice structure can be divided into three groups, namely, coherent (δ ≤ 5%), semi-coherent (5% ≤ δ ≤ 25%), and non-coherent multilayer (δ ≥ 25%) groups. It is known that molecular dynamics (MD) simulation is an effective method to study the deformation and mechanical behavior of materials [24][25][26][27][28]. For example, with MD simulation, Shao et al studied the relaxation mechanisms and misfit dislocation patterns of semi-coherent interfaces in a FCC/FCC multilayered film [29][30][31][32], where FCC is the abbreviation for Face-Centered Cubic.…”