Effect of zirconium addition on the recrystallization behaviour of a commercial Al-Cu-Mg alloy

It is well known that the second phase particles have an effect on recrystallization and grain growth behaviour of an alloy. Particularly the bimodal distribution of second phase particles has an effect which is opposite in sense where coarse second phase particles (> 1 μm) stimulate nucleation while fine particles exhibit Zener drag. In the literature, the effect of zirconium addition to aluminium alloys has been well documented in order to produce superplasticity by giving ultra fine grain size to the alloy. Addition of zirconium produces Al 3 Zr particles which pin the grain boundaries during recrystallization and grain growth. In the present work, zirconium was added to a commercial Al-Cu-Mg alloy and by heat treatment Al 3 Zr particles were precipitated and after forging, the grain size was an order of magnitude lower than the alloy without zirconium. Transmission electron microscopy was employed to characterize the second phase particles, i.e. Al 3 Zr particles and found to be rod shaped and identified to be cubic ordered L 1 2 phase with a lattice parameter of 0.408 nm. Further, it was observed that fine (100 nm) Al 3 Zr particles promote only continuous recrystallization which is polygonization of subgrains and subgrain growth. It was found that the fine dispersion of Al 3 Zr particles inhibits both recrystallization and grain growth in the commercial Al-Cu-Mg alloy.