Energy and electron structure of trace Sc

Zr

respectively

and mixed Sc

Zr adding into Al alloy based on the first-principle pseudopotential plane-wave method were investigated.The results show that the cohesive energies and generation heating of Al-Sc

Al-Mg-Sc

Al

3

Sc

Al-Zr

Al-Mg-Zr

Al

3

Zr

Al-Sc-Zr

Al-Mg-Sc-Zr are higher than those of pure Al and Al-Mg alloy

exhibiting the easy generation and structure stability of these crystal cells in Al-Mg system alloy.Through further analyzing the densities of states （DOS）of the crystal cell

it is found that there are more amounts of bonding electron numbers near the Feimi level of the alloy system with mixed Sc and Zr addition than those of ones with Sc or Zr addition

respectively.The refinement effects of mixed Sc and Zr addition are superior to those of Sc or Zr addition

respectively

which is contributed to more grain as the heterogeneous nucleation sites with mixed Sc and Zr addition during solidification process.