Microstructure evolution of the 1469 Al–Cu–Li–Sc alloy during homogenization

• The formation of the W phase (AlCuSc) was found in the 1469 Al-Cu–Li–Sc alloy.
• The W phase formed during the homogenization process.
• We model the formation process of the W phase.
• The formation of the W phase consumes lots of Cu and Sc atoms.

The present work aims to clarify the formation of the W phase (AlCuSc) and its formation time in the high Cu content alloy with Sc addition. The microstructure evolution during the two-step homogenization annealing process was investigated in the 1469 Al–Cu–Li–Sc alloy. No evidences of the Al3Sc phase and the W phase were found in the solidification structure. The arrays of the W phases were found to form after homogenization. The AlCu phases with traces of Sc that formed during solidification suppose to be the precursor of the W phases, and then transform into the W phases by consuming the Sc atoms that fixed in the supersaturate solid solution. The formation of the W phase inhibits the precipitation of the Al3Sc phase. A corresponding model of the W phase formation mechanism is proposed.