Twinning of second phase and formation of LPSO structure in extruded billets containing Nd magnesium alloy by spray deposition

Abstract:

The deposited billets of Mg-9Al-3Zn-1Mn-9Ca-1Nd alloy were prepared by spray deposition technique and pre-deformed by extrusion (extrusion temperature 340℃, extrusion ratio 25:1). The formation of Mg-Nd-Zn type LPSO structure on the second phase of magnesium alloy and the relationship between the LPSO phase and the twinning of the second phase were studied by means of SEM , TEM and XRD. The results show that the 6H-LPSO structure phase was formed on the Al₂ (Ca,Nd)-type C15 phase. The formation of dislocation entanglement around the C15 particles and the high concentration of stress around C15 particles is the main cause of the twinning of the C15 particles. The nano-scale C15 particles, pinning dislocations and inhibition of recrystallization grain growth, is the main reason for the formation of (0002) basal and prismatic (100) and pyramidal (101) textures. However, it is easy to form LPSO structure phase when the Nd content is higher in the smaller C15 particles, and that of twinning when the Nd content is lower in the larger C15 particles.