Super-plasticity Of Nanowires Upon Loading By Molecular Dynamics Simulation

In this paper, molecular dynamics simulations have been performed to investigate tensile stress-strain properties of Cu, CuInSe2and MgO nanowires using the embedded atom method potential and Buckingham potential. The effects of crystallographic orientation of nanowires, strain rate, temperature and nanowire size are studied. The yield strain, yield stress and elastic modulus are calculated. At last, we study the diffusion bonding between Ti-A1and tensile properties of welded joint from molecular dynamics simulations.Nanowire materials are not just the direct shrinkage of their feature sizes, they may differ from corresponding bulk materials, and behave abnormally due to surface effect and surface stress. For these three nanowires, the stress-strain curves and configuration evolution of nanowires upon loading are studied. We find that nanowires exhibit brittle-ductile transition upon axial loading with higher strain rate at room temperature. The elongation of nanowires may exceed100%and exhibit super-plasticity. The nanowires exhibit brittle fracture when the strain rate is lower. The super-plasticity of nanowires is high sensitive to strain rate. For Cu and CuInSe2nanowires, the higher strain rate induced the non-crystallization transition of nanowires and a great amount of energy may be absorbed during this process. This results lead to the super-plastic of nanowires; For MgO nanowires, the energy may also be absorbed along phase transformation process, and it lead to the super-plasticity of nanowires.The diffusion process of Ti atoms and Al atoms are studied at temperature of700K and pressure of50MPa. The effect of different cooling rates is studied, the interfacial region become amorphous at high cooling rate. The effects of surface roughness are also analyzed and find surface roughness play an important factor in the diffusion process. The tensile properties of welded joint at different strain rate are examined, the results indicate that the sample exhibit more excellent properties at higher strain rate. The deformation mechanism is also studied, twin boundaries can be identified in Ti region and slip lines are found in Al region. The yield strength can reach62%of single-crystalline Ti and74%of single-crystalline Al with the same size and direction.