Twin recrystallization mechanisms and exceptional contribution to texture evolution during annealing in a magnesium alloy

Abstract

The formability and mechanical properties of Mg alloys are strongly related to the crystallographic basal texture. Deformation twins form extensively after mechanical processing. Recrystallized grains originating from twins usually randomize the texture and therefore weaken the strong deformed texture. It is crucial to understand different recrystallization mechanisms as a function of twin type and therefore their corresponding contribution to texture modification. This work shows that the recrystallization volume fraction formed within twins has been completely underestimated. Specifically, recrystallized grains originating from double twins make the main contribution to texture modification, which contrasts to the opposite view that has been reported in the past decades. The preferential nucleation site, subsequent grain growth and evolution of recrystallization texture in double twins has been tracked in individual twins through the whole annealing process for the first time. After annealing for 378 min at 490 C, the volume fraction of total recrystallization was ~75.7%, while the recrystallized volume fraction originating from double twins and double twin-grain boundary intersections was ~52.9%, which represents ~69.9% of the total volume fraction recrystallization. Recrystallization mechanisms related to various twin types, twin variants, twin-twin and twin-grain boundaries intersections are precisely determined. These findings could lead new insight to design new wrought alloys and improve formability of commercial alloys.