Molecular dynamics study on temperature and strain rate dependences of mechanical properties of single crystal Al under uniaxial loading

Based on the embedded atomic method potential energy function, the uniaxial tensile and compressive deformation of nanocrystalline Al with different sizes in the crystal orientation ⟨100⟩ is studied by the atomistic molecular dynamics simulation approach at six different temperatures and three different strain rates. The simulation results show that, under the same simulation condition, the stress–strain curves of nanocrystalline Al in the process of uniaxial tension and compression are asymmetric and there exists a significant difference in the late region of elastic deformation. The reason for the asymmetry lies in the difference in the process that the work done by the surroundings converts into the strain energy of nanocrystalline Al in the deformation process. At the same temperature and strain rate, the tensile elastic modulus and yield strength of nanocrystalline Al are greater than those of compression. With the increase in temperature, the elastic modulus and yield strength of tension and compression gradually decrease and the two values tend to be the same with the increase in temperature. The higher the strain rate, the greater the yield strength and the corresponding yield strain of the nanocrystalline Al. Finally, the effects of size on the tensile and compressive properties of nanocrystalline Al are briefly discussed.