Papers by Author: M. Spychalski

Abstract: In this study a series of 3D models for curved [100] grain boundaries (GBs) in pure α-iron have been constructed. Each model consisted of a spherical grain, with an initial size of about 9 nm, surrounded by a large single-crystal. Different orientations have been assigned to the grain and the matrix in order to obtain interfaces with misorientation angles in the range of 5-45 degrees in steps of 5 degrees. The molecular dynamics with Embedded Atom Method (EAM) potential have been performed for investigation of the temporal changes in GB migration and grain rotations at temperature of 1000 K. The relationship between GB misorientation and its mobility has been found. It was also discovered that the density of the material decreases with a reduction of GB area. The effect of a triple junction on the interface motion has been also studied by introducing a bi-crystal matrix instead of a singlecrystal one. The results are discussed in terms of grain growth investigations in nanometals.

Abstract: In the present study Finite Element Method (FEM) has been applied for modelling of indentation process in polycrystalline metals. Two different models of the material, with linear and non-linear hardening, have been assumed in calculations. The indentation process has been quantitatively described by load-depth curves. The hardness values were obtained from the unloading part of such curves, which are responsible for plastic deformation of the material during indentation process. In addition, the geometry changes of the indent after deformation have been analyzed. The results show that simulation techniques, used in the present study, are useful in estimation of materials hardness. It has been also found that specific combination of materials properties such as hardening exponent, hardening coefficient, tangent modulus and yield stress may result in sink-in or pile-up phenomenon. These processes may influence the indent geometry and hardness measurements consequently.