Optimization of Aluminum Alloy AA5083 for Superplastic and Quick Plastic Forming

The high temperature formability of Al-4.6 wt pct Mg alloys with 0.5-1.5 wt pct Mn and 0.05-0.27 wt pct Fe has been evaluated by uni-axial tensile testing at 698.15 K to 798.15 K (425 °C to 525 °C) with strain rates from 2 × 10⁻⁵ to 8.75 × 10⁻² s⁻¹. The effects of Mn and Fe on the intermetallic phase, grain structure and cavitation were investigated and correlated to the superplastic behaviors. The superplasticity was found to be very dependent on the density, size and volume fraction of the Al₆(Mn, Fe) particles. The increasing Mn and decreasing Fe not only refine and stabilize the grain structure, but also reduce the nucleation rate of cavities. Consequently, the grain boundary sliding is enhanced and the premature failure due to cavitation is retarded, resulting in a significant improvement of superplasticity. With optimized chemistry containing very high Mn, e.g., 1.7-1.9 wt pct, and very low Fe, e.g., below 0.1-0.15 wt pct, the maximum superplasticity could be achieved at 698.15 K to 773.15 K (425 °C to 500 °C) with strain rates from 10⁻⁴ to 10⁻² s⁻¹.