Necklace Formation during Dynamic Recrystallization of 5182 Aluminium Alloy under Isothermal Compression

Dynamic recrystallization (DRX) characteristics of an 5182 Al alloy was investigated at temperatures ranging from 673 K-773 K and constant strain rates of 0.01 s-1, 0.1 s-1, 1 s-1, 10 s-1, and 50 s-1. The average grain size of the as-casted alloy was 160 μm and was refined to 20 μm via deformation at 773 K, 50 s-1 to a strain level of 0.5 (40%). The true stress-strain curves were determined and divided into two main groups based on the temperatures and strain rates. The activation energy of the DRX in the examined aluminum alloys was calculated, being 175,87 kJ/mol. During the crystallization process compound phases were crystallized along the border of initial grains due to the great content of Mg, Mn and Fe. It was deduced from the metallography examination that most of the new grains formed via necklacing mechanism from the mentioned borders during the DRX.