(1. 兰州理工大学 材料科学与工程学院 省部共建有色金属先进加工与再利用国家重点实验室，兰州 730050； 2. 兰石铸造有限公司，兰州 730050)
摘 要: 采用X射线衍射仪、金相显微镜、扫描电镜、透射电镜及显微硬度计等研究挤压Mg-2Dy-0.5Cu(摩尔分数，%)合金板材的显微组织及时效硬化行为。结果表明：铸态合金主要由α-Mg枝晶、分布在枝晶间片层状的18R-LPSO相以及少量不规则的MgDy3颗粒相组成。挤压后，合金发生动态再结晶，粗大的LPSO相碎化并沿挤压方向排列，少量细小片层状的14H-LPSO相在再结晶的α-Mg晶粒内析出。随着时效时间的增加，14H-LPSO相的体积分数逐渐增加并粗化，合金的硬度增加且在72 h达到峰值。合金峰值硬度的产生主要归结为高体积分数14H-LPSO相的析出强化。
关键字: Mg-Dy-Cu合金板材；LPSO相；显微组织；时效行为
（1. State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China; 2. Lanshi Foundry Co., Ltd., Lanzhou 730050, China）
Abstract:The microstructure and age-hardening behavior of an extruded Mg-2Dy-0.5Cu (mole fraction, %) alloy sheet were investigated by X-ray diffractometer, optical microscopy, scanning electron microscopy, transmission electron microscopy and microlardness tester. The microstructures of the as-cast alloy mainly consist of α-Mg dendrites, the 18R-long period stacking ordered (LPSO) phase distributes among α-Mg dendrites and a small number of MgDy3 particle phases. After extrusion, dynamic recrystallization (DRX) occurs and fine microstructure is obtained during extrusion. Some coarse 18R-LPSO phases are crushed and distributed along the hot extrusion direction. Moreover, few fine lamellar 14H-LPSO phases precipitate in DRX α-Mg grains. With the increase of aging time, the volume fraction of 14H-LPSO phase gradually increases and the phases coarsen, the hardness of the alloy increases and reaches a peak at 72 h, which is mainly attributed to the precipitation strengthening of the high volume fraction of 14H-LPSO phase.
Key words: Mg-Dy-Cu alloy sheet; LPSO phase, microstructure; aging behavior
