(1.中南工业大学材料科学与工程系，长沙410083；
2.西南铝加工厂，重庆631326)
摘 要: 通过微观组织分析，研究了LY12挤压棒材在固溶处理前进行足够的冷拔变形可消除其粗晶环的现象。足够的冷变形增加了再结晶的形核率，改变了第二相粒子、残余应力的大小和分布，从而获得了均匀的细晶组织，消除了粗晶环。由此还分析了LY12CZ挤压棒粗晶环形成的原因，即挤压过程中棒材边部剧烈的剪切变形使其具有很大的畸变能，促使第二相粒子聚集长大而失去对再结晶的抑制作用，在随后的淬火加热过程中发生一次再结晶而聚集长大形成粗晶环。
关键字: LY12铝合金 粗晶环 冷拉拔
COARSE-GRAIN RECRYSTALLIZATION ANNULUS OF
EXTRUDED BARS OF LY12CZ ALUMINIUM ALLOY
（1．Department of Materials Science and Engineering,
Central South University of Technology, Changsha 410083
2.Southwestern Aluminium Fabrication Plant, Chongqing631326）
Abstract:It has been studied by analyzing the microstructure that the coarse-grain recrystallization annulus in directly extruded LY12 aluminium alloy bars can be eliminated by sufficient cold drawing reduction before solid solution. The nucleation of recrystallization increases by certain cold drawing reduction.Cold drawing results in more homogeneous distribution of residual stress so that the elimination of coarse grain annulus and homogeneous fine grain structure can be achieved.The mechanism of the formation of the annulus in LY12CZ bars was discussed as well.It is concluded that the formation of the annulus can be essentially attributed to the violent shear deformation during hot extruding. Large shear strain brings large distortion energy to the outer layer of the products, thus facilitating the gathering of the particles containing manganese, and making them lose the retardation to recrystallization grain growth. Consequently, the nuclei formed by subgrain coalescence grow up accumulatively to form coarse recrystallization annulus during subsequent reheating and soaking processes before quenching.
Key words: LY12 aluminium alloy coarse-grain recrystallization annulus cold drawing
