Secondary recrystallisation in magnox AL 80

Exaggerated grain growth observed in the magnesium canning alloy Magnox AL 80 (Al/0.8 wt %, Be/0.004 wt %) is typical of the phenomenon classified by Burgers as "Secondary Becrystallisation". Studies upon alloys of varying composition indicate that the presence of 40 ppm beryllium is of particular importance in promoting the effect. Metallographie observations indicate that both marked equilibrium segregation and precipitation occur at the grain boundaries of the fine-grained alloy. It is suggested that normal grain growth is restricted and the conditions for secondary recrystallisation realised, by the combined pinning action of the precipitates and equilibrium segregates. A rotation of 24 {1}/{2}° or 35 {1}/{2}° about the [0001]axis accompanies secondary recrystallisation, but the exact role of texture in relation to the phenomenon has not been clearly defined.