轧制变形对喷射沉积含Nd镁合金织构及LPSO相的影响

EFFECTS OF ROLLING DEFORMATION ON TEXTURE AND LPSO PHASE OF SPRAY-DEPOSITED MAGNESIUM ALLOYS CONTAINING Nd

采用喷射沉积技术制备Mg-9Al-3Zn-1Mn-6Ca-2Nd合金沉积坯,对其进行挤压预变形和轧制变形(温度T=350℃;道次压下率e=20%,25%,30%).利用SEM,TEM和XRD研究二次变形对尺寸不对称挤压坯中织构演变及LPSO相形成的影响.结果表明:镁合金板坯经350℃和道次压下率为20%轧制后,在(Ca,Nd)Al2结构C15型Laves相基体形成24R结构Mg-Nd-Zn型LPSO相;随着轧制变形程度增大(e=20%,25%,30%)实现了形变织构的随机化,纳米级C15粒子钉扎位错与亚晶引起的再结晶的共同作用是导致基面织构(0002),柱面织构{1010}<0001>及锥面织构{1012}全面启动的主要原因.

Mg alloys have been applied widely as structural materials over the past decades, with low densi- ty, high specific strength, stiffness, specific elastic modulus, and high recycling rate. However, their features of poor ductility and formability at room temperature have limited their application due to hexagonal close-packed crystal structure with less independent slip systems. Grain refinement and texture randomization are two means to activate other slip systems. In this work, the billets of Mg-9Al-3Zn-1Mn-6Ca-2Nd alloy produced by spraying de- position method （the Osprey process） were studied in order to analyze the effect of rolling deformation at 350 ℃ and pass reduction ε=20%, 25% and 30% on texture and microstructure evolution of an extruded size-asymmetry Mg alloy by SEM, TEM and XRD. The results show that under the condition of reduction of ε=20% at 350 ℃, a long-period stacking ordered phase with 24R structure was formed in （Ca, Nd）Al2 phase （C 15 Laves phase ）. All of basal texture （0002）, prismatic texture { 1010 } 〈0001 〉, and pyramidal texture { 1012 } were activated, with pole den- sity level weakened while pass reduction increased （ε=20%, 25% and 30% ）, namely, texture randomization achieved in Mg alloy, with main causes of nanometer-sized dispersed C 15 phase impeding dislocation movementand sub-cells inducing the process of recrystallization.