Abstract:High-resolution transmission electron microscopy (TEM), X-ray diffractometry (XRD), energy dispersive spectroscopy (EDS) and hardness test were used to study the re-dissolution and re-precipitation behavior of nano-precipitates of the spray-formed fine-grained Al-Cu-Mg alloy during rapid cold stamping deformation. Results show that the extruded Al-Cu-Mg alloy undergoes obvious re-dissolution and re-precipitation during the rapid cold-stamping deformation process. The plastic θ′ phase has a slower re-dissolution rate than the brittle S′ phase. The long strip-shaped S′ phases and the acicular θ′ phases in Al-Cu-Mg alloy after three passes of cold stamping basically re-dissolved to form a supersaturated solid solution. A large number of fine granular balance θ phases precipitate after four passes of rapid cold-stamping deformation. Rapid cold stamping deformation causes the S′ phase and θ′ phase to break and promote the nano-precipitate phases to re-dissolve. The high distortion free energy of the matrix promotes the precipitation of the equilibrium θ phase, and the hardness of the alloy obviously increases from HB 55 to HB 125 after the rapid cold stamping process.

Key words: Al-Cu-Mg alloy; rapid cold stamping; nano-precipitate; re-dissolution; re-precipitation