(1. 華南理工大學(xué) 機(jī)械與汽車工程學(xué)院，廣州 510640；
2. 華南理工大學(xué) 國家金屬材料近凈成形工程技術(shù)研究中心，廣州 510640)
摘 要: 采用劇塑性變形工藝(等通道轉(zhuǎn)角擠壓和軋制)以及隨后的短時間退火制備高性能Mg-Li合金，通過顯微組織觀察、掃描電鏡分析、X射線衍射儀測試和室溫拉伸測試等研究變形前后合金組織、力學(xué)性能及強(qiáng)化機(jī)制。結(jié)果表明：合金鑄態(tài)晶粒粗大，主相為β相，α相分布于β相的晶界以及晶內(nèi)；同時，晶內(nèi)存在大量Al2Y和AlLi析出相。由于動態(tài)回復(fù)作用顯著，合金變形時并未發(fā)生明顯的動態(tài)再結(jié)晶現(xiàn)象；經(jīng)短時間退火后，合金組織發(fā)生完全再結(jié)晶，其晶粒細(xì)化至27.1 μm(12pra工藝，即等通道轉(zhuǎn)角擠壓、軋制及退火)。鑄態(tài)合金的抗拉強(qiáng)度和伸長率分別為131.1 MPa和47.1%；經(jīng)12pr(等通道轉(zhuǎn)角擠壓及軋制)變形后，合金的伸長率達(dá)到90.5%，而抗拉強(qiáng)度稍有提高，這主要受位錯協(xié)調(diào)變形及動態(tài)回復(fù)作用的影響；退火后合金的伸長率顯著降低而強(qiáng)度提高至237.6 MPa (12pra)，出現(xiàn)退火致強(qiáng)化現(xiàn)象，其主要的機(jī)制是有限位錯源強(qiáng)化及晶界強(qiáng)化。
關(guān)鍵字: Mg-Li合金；等通道轉(zhuǎn)角擠壓；軋制；退火；顯微組織；力學(xué)性能
（1. School of Mechanical and Automotive Engineering, South China University of Technology,
Guangzhou 510640, China;
2. National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials,
South China University of Technology, Guangzhou 510640, China）
Abstract:The microstructure, mechanical properties and strengthening mechanism of Mg-Li alloys processed by severe plastic deformation (equal channel angular pressing (ECAP) and rolling) and subsequent annealing were analyzed by OM, SEM, XRD and tensile testing. The results show that the initial grains of the as-cast alloy are coarse and β phase occupies the main position, while α phase distributes inside or in the boundary. Meanwhile, there are lots of precipitate phases Al2Y and AlLi in the grain. Obvious dynamic recrystallization (DRX) does not occur during the deformation due to the significant effect of dynamic recovery (DR). After a short time annealing, the alloy is completely recrystallized with grain size refined to 27.1 μm (process of 12pra: ECAP, rolling and annealing). The tensile strength and elongation of the as-cast alloy are 131.1 MPa and 47.1%, respectively. After the process of 12pr (ECAP and rolling), the elongation of the alloy reaches 90.5%, while the tensile strength is improved slightly. This can be explained based on the effect of DR and dislocation-coordinated deformation. Subsequent annealing treatment results in an increase in tensile strength (12pra: 237.6 MPa) and a significant decrease in elongation because of the dislocation source-limited hardening and grain boundary strengthening mechanism.
Key words: Mg-Li alloy; equal channel angular pressing; rolling; annealing; microstructure; mechanical property
