(1. 蘭州理工大學(xué) 材料科學(xué)與工程學(xué)院 省部共建有色金屬先進加工與再利用國家重點實驗室，蘭州 730050； 2. 蘭石鑄造有限公司，蘭州 730050)
摘 要: 采用X射線衍射儀、金相顯微鏡、掃描電鏡、透射電鏡及顯微硬度計等研究擠壓Mg-2Dy-0.5Cu(摩爾分數(shù)，%)合金板材的顯微組織及時效硬化行為。結(jié)果表明：鑄態(tài)合金主要由α-Mg枝晶、分布在枝晶間片層狀的18R-LPSO相以及少量不規(guī)則的MgDy3顆粒相組成。擠壓后，合金發(fā)生動態(tài)再結(jié)晶，粗大的LPSO相碎化并沿擠壓方向排列，少量細小片層狀的14H-LPSO相在再結(jié)晶的α-Mg晶粒內(nèi)析出。隨著時效時間的增加，14H-LPSO相的體積分數(shù)逐漸增加并粗化，合金的硬度增加且在72 h達到峰值。合金峰值硬度的產(chǎn)生主要歸結(jié)為高體積分數(shù)14H-LPSO相的析出強化。
關(guān)鍵字: Mg-Dy-Cu合金板材；LPSO相；顯微組織；時效行為
（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
