Molecular Dynamics Study On Plastic Deformation Mechanism Of Titanium Crystal

The metal titanium is one of the most important structural materials in 21st century, due to its excellent performance and has been widely used in various fields. The plastic deformation mechanism of titanium has been a focus for researchers. In this paper, through the method of molecular dynamics, the plastic deformation mechanism of single crystal titanium has been investigated.With an embedded atomic potential (EAM) and molecular dynamic (MD)method, deformation model of shear, tensile and compression have been established and plastic deformation behaviour have been investigated on titanium through different loading style. The influence of temperature, size and tensile speed on the properties of titanium has been analyzed. The main conclusions are as follow: An embedded atomic potential (EAM) was selected and used to simulated the melting point, the formation energy of vacancy of titanium to check its accuracy and efficacy. The calculated melt point temperature and the formation energy of a vacancy are 1920K and 1.469 eV, respectively. These values are very close to the experimental findings, providing strong evidence that this EAM could be used to simulate the plastic deformations of titanium.MD model of shear deformation along (0001)[2110] and (1010)[2110] have been established and the influence of shearing direction on deformation behaviour have been compared. The result shows that the initial stress and strain of plastic deformation are 0.27GPa, 0.05 and 0.57GPa, 0.18 respectively for shearing along (0001)[2110] and (1010)[2110], with deforming speed 0.01nm/ps, 300K. Shear deformation along basal plane is easier than prismatic plane.Model of tensile deformation with tensile direction along [0001] and [ 0110] have been established. The results show that tensile process of both two directions contains four stages, ie, elastic deformation, uniform plastic deformation, necking and fracture. The slip system is few and the orientation deviates from the soft orientation when tension applied along [0001]. The yielding stress and strain are 3.55GPa and 0.095 respectively while the fracture strain is 0.55. For [ 0110] tension, the slip system is more and the orientation is close to soft orientation. The yielding stress and strain are 2.41GPa and 0.067 respectively while the fracture strain is 1.28. The plastic deformation along [0110] tension is easier as well as the plasticity is better.Model of compression deformation with compress applied along [0110] has been established and the process of deformation has been investigated. The result shows that curve of stress vs strain implies three deforming stages, ie, elastic, yielding, and hardening. The slip system is close to soft orientation. The yielding stress and strain are 2.42GPa, 0.04 respectively, with the same yielding stress as [0110] tension.