Formation of Dislocations and Twins As a Result of Uniaxial Compression of Magnesium Single Crystals: Molecular Dynamics
- PDF / 2,209,916 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 161 Views
STRUCTURE OF CRYSTALS
Formation of Dislocations and Twins As a Result of Uniaxial Compression of Magnesium Single Crystals: Molecular Dynamics Simulation A. M. Vlasovaa,b,* and A. Yu. Nikonovc a Miheev
Institute of Metal Physics, Ural Branch, Russian Academy of Sciences, Yekaterinburg, 620041 Russia Ural Federal University named after the First President of Russia B.N. Yeltsin, Yekaterinburg, 620002 Russia c Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences, Tomsk, 634021 Russia *e-mail: [email protected] b
Received January 27, 2017
Abstract—An atomistic simulation of the deformation of ideal magnesium crystal along the [1120] crystallographic axis has been performed. The evolution of structural defects under load at T = 300–350 K is considered in detail. It is established that the nucleation of dislocations in an ideal crystal occurs when the stress reaches a level of 0.1G (G is the shear modulus). The acting deformation modes are found to be prismatic slip of a dislocations and {10 13} twinning. The formation of dislocation networks and dislocation sites in the twinning plane is observed. Some reactions are proposed to describe the dislocation evolution in the (3034) plane. DOI: 10.1134/S1063774518030318
INTRODUCTION Currently, molecular dynamics simulation is widely used to imitate various effects on solids, such as synthesis, melting, crystallization, amorphization, phase transitions, and radiation-induced structural changes under nuclear fuel irradiation. The objects of study are both organic and inorganic chemical compounds with different stoichiometries, polymers, metals, alloys, and solid solutions. Qualitative and quantitative characteristics of physical properties, which change under the effect studied, can be calculated. The dislocation structure of metals and alloys has been studied by transmission electron microscopy since the 1960s. In the course of time, the interest of researchers changed from cubic to hexagonal crystals. However, not all lattice-induced phenomena and properties can be predicted and explained proceeding from only the observations of the dislocation structures formed under stress and temperature effects. For example, the deformation characteristics of magnesium, which has a number of unique properties (including superplasticity, temperature anomaly of yield stress, self-blocking of (с + a) dislocations, and good sorption capacity with respect to hydrogen), are not quite clear because of the large number of its deformation modes, which are active at certain stresses and different temperatures. Due to the intense development of computational technologies, a great number of interaction potentials for hexagonal crystals have been investigated in the last
years using different methods, primarily, the embedded-atom method [1]. As a result, one can not only study the dislocation core structure for HCP metals, but also trace the plastic flow at the atomic level, and, therefore, analyze the dynamics of dislocations under applied stress. The
Data Loading...
