喷射沉积含Nd镁合金挤压坯中第二相孪生与LPSO结构相形成

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

摘要:

采用喷射沉积技术制备Mg-9Al-3Zn-1Mn-9Ca-1Nd合金沉积坯,对其进行挤压预变形(挤压温度为340 ℃,挤压比为25:1)。利用SEM,TEM和XRD研究镁合金第二相上孪生、Mg-Nd-Zn型LPSO结构相的形成以及LSPO结构相与第二相孪生之间的关系。结果表明：在Al₂(Ca,Nd)型C15相上形成了6H-LPSO结构相,C15粒子周围应力高度集中使分切应力提高且C15粒子周围形成的位错缠结区是C15粒子发生孪生的主要原因；纳米级C15粒子钉扎位错、抑制再结晶晶粒长大是(0002)基面织构及柱面(100)和锥面(101)织构形成的主要原因；当平均尺寸较小的C15粒子内Nd含量较高时C15粒子易形成LPSO结构相,而平均尺寸较大的C15粒子内Nd含量较低时C15粒子易发生孪生。

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.