First-Principles Investigation of Point Defects on the Thermal Conductivity and Mechanical Properties of Aluminum at Room Temperature

The effects of point defects on the mechanical and thermal conductivity of aluminum at room temperature have been investigated based on the first-principles calculations combined with the Boltzmann equation and the Debye model. The calculated results showed the equilibrium lattice constants a0 of all REAl are larger than that of Al, and the defective formation energy Ef of all REAl is lower than that of VAl. Both a0 and Ef increase from Sc to La and then decrease linearly to Lu. The effects of solute atoms on the mechanical properties of the Al matrix were further calculated, and compared with Al, it is found that the REAl defects decrease the elastic constant Cij, Cauchy pressure C12–C44, bulk modulus B, shear modulus G, Young’s modulus E, B/G and Poisson’s ratio ν of Al, except for C44 of REAl (RE = La-Nd). With the increase of atomic number, the C11 and E of Al-containing REAl decrease from Sc to La and then slowly increase to Lu, whereas C12, C44, B, and G have little change. Meanwhile, the values of C12–C44 and B/G of Al-containing REAl increase from Sc to Ce, and it slightly change after Ce, while ν is nearly unchanged. All defects containing Al present nonuniform and ductility. Finally, the effects of rare earth (RE) atoms on the thermal conductivity (TC) of Al alloys have been investigated based on the first-principles calculations. The reduction of TC of Al alloys by RE solute atoms REAl is much greater than that by the L12 Al3RE phase with the same concentration of RE, which is in good agreement with the experiments. With the RE atomic number increasing, the total TC κ of the Al-RE solid solution decreases from Sc to La firstly and then increases linearly to Lu. Moreover, the decrement of TC Δκ of the Al matrix by early REAl (RE = La-Sm) is larger than that by VAl, while the later REAl (RE = Gd-Lu) shows the opposite influence.