Continuous dynamic recrystallization in magnesium alloy

Dynamic process of new grain formation was studied in a coarse-grained Mg-Zn-Zr alloy deformed at elevated temperatures. The samples were mainly compressed in air to strains of 0.1 and 0.25 at a temperature of 523K and at strain rate of 2.8x10(-3) s(-1). Crystal orientations of neighboring grains and subgrains were measured using a conventional Kikuchi-line technique. Hot deformation promotes the formation of a new grain structure and a gradual increase of the misorientations of (sub)grain boundaries up to high angle ones. These results lead that the development of new grains in the magnesium alloy can occur by continuous dynamic recrystallization (CDRX). The fact that CDRX occurred in the Mg alloy with a low stacking fault energy (SFE) may be associated with operation of a specific mechanism of plastic deformation in the zones of enhanced plastic activity at and near original grain and twin boundaries. The formation of new grains can be connected with extensive cross-slip of a dislocations in vicinity of pre-existing high angle boundaries which could provide the formation of subgrain structure and quick misorientation increase by cross-slip of screw a dislocations across subgrains and accumulation into subgrain boundaries. Such behavior is associated with decreased splitting width of a dislocations and growing of SFE of cross-slipped dislocations that is likely to provide the development of the "high SFE metal" type of DRX in magnesium alloy.