Solid solution strengthening mechanism in high pressure die casting Al-Ce-Mg alloys

A series of Al-xCe (x = 2, 4, 6, 8, 10 wt%) and Al-8Ce-yMg (y = 0, 0.10, 0.25, 0.50, 0.75 wt%) alloys were prepared by high-pressure die casting. The introduced cerium element promoted the nucleation of alpha-Al grains. Al11Ce3 phase served as the heterogeneous nucleation substrate of alpha-Al due to the small lattice mismatch of 6.72%. According to the results calculated by Nelson-Riley extrapolation function, the lattice constant of alpha-Al increased from 4.0511 angstrom to 4.0540 angstrom with the increasing of Mg content from 0 wt% to 0.75 wt%. Due to the solid solution strengthening effect of Mg atoms, the yield strength of Al-8Ce-yMg alloys and the hardness of alpha-Al matrix in the Al-8Ce-yMg alloys showed a parabolically increasing tendency, from 92 MPa to 115 MPa and 0.502 GPa-0.575 GPa, respectively. The work hardening capacity of Al-8Ce-yMg alloys was improved by the solid solution of Mg with the work hardening exponent increasing from 0.21 to 0.27. The solid solution of Mg atoms reduced the stacking fault energy of Al-8Ce-yMg alloys and suppressed the dynamic recovery process of the alloys during deformation process, which promoted the formation of dislocation tangles and dislocation networks in the alpha-Al matrix.

Automated summary

The introduction of cerium promoted nucleation of alpha-Al grains and Al11Ce3 phase served as the heterogeneous nucleation substrate of alpha-Al due to small lattice mismatch. The lattice constant of alpha-Al increased with increasing Mg content, enhancing yield strength and hardness due to solid solution strengthening effect. Mg atom solid solution improved work hardening capacity by increasing work hardening exponent and reducing stacking fault energy, promoting dislocation tangles and networks in the alpha-Al matrix.