(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083；
2. 湖南工學(xué)院 機械工程系，衡陽 421008)
摘 要: 對初始晶粒度為66 μm的軋制板材在不同溫度和不同變形速率下進行超塑性拉伸實驗，研究Mg-Gd-Y-Zr合金粗晶熱軋板材的超塑性行為與微結(jié)構(gòu)特征。在溫度為435 ℃、應(yīng)變速率為5×10−4 s−1的變形條件下獲得的最大伸長率為380%，應(yīng)變速率敏感系數(shù)為0.56。合金的表觀變形激活能高于鎂的晶界擴散激活能或晶格擴散激活能；合金的超塑性變形機制為晶格擴散控制的位錯協(xié)調(diào)晶界滑動機制。微結(jié)構(gòu)分析結(jié)果表明：第二相釘軋晶界，較軟的不規(guī)則塊狀的β相承受了部分塑性變形。
關(guān)鍵字: Mg-Gd-Y-Zr合金；熱軋；第二相；超塑性變形行為；微結(jié)構(gòu)
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Department of Mechanical Engineering, Hunan Institute of Technology, Hengyang 421008, China）
Abstract:The superplastic behavior and microstructural characteristics of coarse-grained Mg-Gd-Y-Zr rolled sheet with initial grain size of 66 µm were investigated systematically, the tensile tests at various temperatures and strain rates were conducted. The results show that the sheet exhibits a maximum elongation of 380% and a sensitivity coefficient of strain rate of 0.56 at 435 ℃ and 5×10−4 s−1. The apparent activation energy of this alloy is larger than the diffusion activation energy of grain bound or lattice diffusion energy of Mg. The superplastic behavior is attributed to grain boundary sliding accommodated by dislocation motion assisted by lattice diffusion. It is suggested from microstructural analysis results that the second phases exhibit significant effect of pinning grain boundaries, and that β phase deforms and the strain partly transfers from the matrix to the β phase.
Key words: Mg-Gd-Y-Zr alloy; hot rolling; second phase; superplastic behavior; microstructure
