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ε =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(ε =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{100}<0001>及锥面织构{102}全面启动的主要原因.
Mg alloys have been applied widely as structural materials over the past decades, with low density, 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 deposition 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 (C15 Laves phase ). All of basal texture (0002), prismatic texture {100}<0001>, and pyramidal texture {102} were activated, with pole density 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 C15 phase impeding dislocation movement and sub-cells inducing the process of recrystallization.
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