Tensile Microstructure Evolution Of [110], [1(?)2], [1(?)(?)] Crystals To Tungsten Nanowires

As the international energy problem more and more seriously, the more eyes has been focused on. Fusion energy is standing out in that it is safe and clear energy, the superior physical and chemical properties of tungsten make tungsten famous in nano-materials investigation.Mechanical properties and micro-structure fracture mechanism of tungsten nanowires with crystal orientations of [110], [1(?)2] and [1(?)(?)] have been investigated with molecular dynamics and embedded atom methods. Simultaneously common neighbor analysis(CNA), center symmetry parameters(CSP) and coordination number(CN) have been employed to analysis the evolution of structure. It is concluded that different crystal orientation nanowires have different characters. The elastic modulus, yield strain, yield strength and the fracture stress decrease in the sequence of [1(?)(?)], [110] and [1(?)2] crystal orientations. It also reveals that all of the stress-strain curves are classified into four stages:elastic stage, damage stage, yielding stage and failure stage. It concluded that crystal orientation has slightly impact on the elastic modulus but has great effect on the tensile strength, yield strength and ductility. Interestingly, hardening stage has been found in tungsten nanowire with crystal orientation of [1(?)2] at yielding stage. That is to say, the strain increases with the increase of stress in the hardening stage, in the end the tensile failure mechanisms of the three nanowires have been summarized.Secondly, the mechanical properties of [1(?)2] and [110] nanowires were studied under the circumstance of uni-axial tension in different strain rate. It shows that there is nothing influence in elastic modulus when change the strain rate and all of the nanowires appear super-ductility in the high strain rate. Fracture mechanisms were proposed in different strain rate in the end. Moreover, the critical point and hardening vacuum area were found in [1(?)2] nanowire.Finally, the mechanical properties of [1(?)2] and [110] nanowire were investigated, it reveals that temperature has no impact on the elastic modulus in low temperature and the elastic modulus is decreasing with the increase of the temperature in [1(?)2] nanowire. Interestingly, the existence of the hardening stage is none of buiseness with the temperature. The secondary defects retain mechanism has been found in 120K and 150K. All of the mechnical properties are decreasing with the increasing of the temperature.