( 1. 郑州大学 材料科学与工程学院，郑州 450002；
2. 清华大学 材料科学与工程系， 北京 100084)
摘 要: 研究了Al3Ti4B中间合金对Mg-7Al-0.4Zn-0.2Mn合金的显微组织、 力学性能及耐腐蚀性能的影响。 结果表明： 当Al3Ti4B加入量小于0.3%(质量分数)时， 合金的平均晶粒尺寸显著减小； 当Al3Ti4B加入量为0.3%时， 合金组织显著细化， 平均晶粒尺寸由未变质合金的135 μm细化到30 μm， 合金拉伸力学性能和耐腐蚀性能最好; 当加入量超过0.3%时， 晶粒粗化； 具有密排六方结构的高熔点化合物TiB2(θm=2 980 ℃)和AlB2(θm=980 ℃)均可作为α-Mg的异质核心， 大量异质结晶核心的存在是导致α-Mg晶粒细化的主要原因。
关键字: Mg-7Al-0.4Zn-0.2Mn合金； Al3Ti4B； 晶粒细化； 异质形核
Mg-7Al-0.4Zn-0.2Mn alloys
（ 1. College of Materials Science and Engineering,
Zhengzhou University, Zhengzhou 450002, China;
2. Department of Materials Science and Engineering,
Tsinghua University, Beijing 100084, China）
Abstract: The effects of Al3Ti4B master alloy on microstructure, mechanical and corrosion resisting properties of Mg-7Al-0.4Zn-0.2Mn alloys were studied. The results show that the average grain size of alloy decreases when the addition of Al3Ti4B is less than 0.3%(mass fraction). The microstructure is refined remarkably when adding 0.3% Al3Ti4B, the average grain size decreases from 135 to 30 μm. When the Al3Ti4B addition is more than 0.3%, the grain size increases with the increase of Al3Ti4B. The mechanical properties and corrosion resisting properties of alloys with 0.3%Al3Ti4B are the best. High melting point compounds (TiB2 and AlB2) with hexagonal closed-packed(HCP) crystal structure can serve as the nucleating sites of α-Mg during solidification, and heterogeneous nucleation is the main reason of the grain refinement of α-Mg grains.
Key words: Mg-7Al-0.4Zn-0.2Mn alloy; Al3Ti4B; grain refinement; heterogeneous nucleation
