Sb变质对原位Mg2Si/AZ91复合材料组织的影响  

Effect of Sb Metamorphism on Microstructure of In-Situ Mg2Si/AZ91 Composites

作　　者：杨莎莎 高义民[1,2] 肖鹏 徐飞行[1,2] 李烨飞 YANG Shasha;GAO Yimin;XIAO Peng;XU Feixing;LI Yefei(State Key Laboratory for Mechanical Behavior of Materials,Xi’an Jiaotong University,Xi’an 710049,China;Institute of Foundry Technology and Wear Resistant Materials,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学金属材料强度国家重点实验室,西安710049 [2]西安交通大学铸造及耐磨材料研究所,西安710049

出　　处：《西安交通大学学报》2019年第10期48-56,共9页Journal of Xi'an Jiaotong University

基　　金：广东省科技计划资助项目（21015B010122003）;广州市科技计划资助项目（201604046009）;陕西省自然科学基金资助项目（2018JM5002）

摘　　要：Mg2Si颗粒增强镁基复合材料中Mg2Si是粗大的长条状,严重降低其力学性能。加入微量Sb元素可细化Mg2Si增强相,但是Sb在Mg2Si/AZ91复合材料中的细化机理尚不明确。为此,采用原位铸造的方法研究了不同Sb含量对Mg2Si/AZ91复合材料微观组织的影响。通过光学显微镜、扫描电子显微镜和电子探针显微分析仪观测了不同Sb含量的Mg2Si/AZ91复合材料中Mg2Si的尺寸和形貌,并探究Sb元素细化Mg2Si的机理。采用Image-Pro Plus软件统计了Mg2Si颗粒的平均尺寸以及形状因子的变化。实验结果表明:添加Sb后基体中汉字状的共晶Mg2Si消失,且初生Mg2Si的平均尺寸不断降低,当Sb的质量分数为2%时,初生Mg2Si颗粒尺寸细化至13.8μm(降低80.1%),分布更均匀;随着Sb含量增加,Mg2Si形状因子越来越趋向于1,形貌由粗大的树突状、长条状转变成细小的多边形;在凝固过程中,Sb富集在Mg2Si固液生长界面前沿,降低了初生Mg2Si的实际析出温度和Mg2Si与熔体的界面张力,提高了过冷度,增大了Mg2Si的形核率。同时,富集在Mg2Si表面的Sb毒化了Mg2Si的生长步骤,Mg2Si各向同性生长,形貌得到改善。Large Mg2Si particles in in-situ Mg2Si particulate reinforced magnesium matrix composites seriously reduce its mechanical properties.The addition of tiny amounts of Sb can refine the Mg2Si reinforcements,but the refinement mechanism of Sb element in Mg2Si/AZ91 composites is not clarified yet.Effects of different Sb content on the microstructure of Mg2Si/AZ91 composites prepared by in situ casting are studied.The size and morphology of Mg2Si in Mg2Si/AZ91 composites with different Sb contents are observed by optical microscope,scanning electron microscope and electron microprobe micro-analysis,and the mechanism of Mg2Si refinement by Sb element is investigated.The average size and the shape factor of Mg2Si particles are counted by Image-Pro Plus software.Experimental results show that with the addition of Sb,the Chinese characters-like eutectic Mg2Si is no longer formed in the matrix and the size of primary Mg2Si keeps decreasing.When the mass fraction of Sb is 2%,the particle size of primary Mg2Si is refined to 13.8μm(a 80.1%reduction),with a more uniform distribution.With the increase of Sb content,the shape factor of Mg2Si tends to 1,and the morphology of primary Mg2Si is changed from the coarse dendritic and long strip shape to small polygon.On the one hand,Sb is enriched at the front of Mg2Si solid-liquid growth interface during the solidification,which reduces the actual precipitation temperature of primary Mg2Si and the interfacial tension between Mg2Si and the melt,improves the degree of undercooling and thus increases the nucleation rate of Mg2Si.On the other hand,a large amount of Sb enriched on the surface of Mg2Si poisons the growth step of Mg2Si,leading to isotopic growth and better morphology.

关 键 词：Mg2Si/AZ91复合材料 Sb元素 Mg2Si细化机理 微观组织 

分 类 号：TG292[金属学及工艺—铸造]