Effect of iron bicrystal orientation on mechanical properties and dislocation density using molecular dynamics simulations of nanoindentation

S. Zahabi, N. Nouri, S. Ziaei-Rad and M.S. Talaei

Mechanics of Advanced Materials and Structures, Volume 29, Issue 9, September 2020, Pages 1243-1256

ABSTRACT

This study concerns the effect of bicrystal spatial orientation on the iron Σ5 boundary under nanoindentation tests. The orientation of the bicrystal is changed relative to the indenter by the parameter “nanoindentation angle” to create dislocation collisions with grain boundary in different directions and to determine the possibility of transmission of these dislocations through the grain boundary. Simulations were carried out for nanoindentation angles between −90° and 90° with a resolution of 18°. Molecular dynamics with EAM atomic potential functions are employed for the simulations. The effect of nanoindentation angle on the crystals Young’s modulus, shear stress, hardness, and Poisson’s ratio were determined. Due to the periodicity which has been observed in all of the aforementioned quantities of the rotated crystal, analytical equations were extracted by adapting the Fourier series expansion on the calculated data. Some explanations were provided for the dislocation behaviors based on the physics of the problem and also by the results reported in the literature. Simultaneous effects of Poisson’s ratio and pile-ups on each other were also investigated and interpreted.

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