( 1. 鄭州大學(xué) 材料科學(xué)與工程學(xué)院，鄭州 450002；
2. 清華大學(xué) 材料科學(xué)與工程系， 北京 100084)
摘 要: 研究了Al3Ti4B中間合金對Mg-7Al-0.4Zn-0.2Mn合金的顯微組織、 力學(xué)性能及耐腐蝕性能的影響。 結(jié)果表明： 當(dāng)Al3Ti4B加入量小于0.3%(質(zhì)量分?jǐn)?shù))時， 合金的平均晶粒尺寸顯著減小； 當(dāng)Al3Ti4B加入量為0.3%時， 合金組織顯著細(xì)化， 平均晶粒尺寸由未變質(zhì)合金的135 μm細(xì)化到30 μm， 合金拉伸力學(xué)性能和耐腐蝕性能最好; 當(dāng)加入量超過0.3%時， 晶粒粗化； 具有密排六方結(jié)構(gòu)的高熔點(diǎn)化合物TiB2(θm=2 980 ℃)和AlB2(θm=980 ℃)均可作為α-Mg的異質(zhì)核心， 大量異質(zhì)結(jié)晶核心的存在是導(dǎo)致α-Mg晶粒細(xì)化的主要原因。
關(guān)鍵字: Mg-7Al-0.4Zn-0.2Mn合金； Al3Ti4B； 晶粒細(xì)化； 異質(zhì)形核
Mg-7Al-0.4Zn-0.2Mn alloys
WANG Li-guo1, LI Jian-guo2
（ 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
