【作者】 赵全友；

【导师】 韩伟；

【作者基本信息】 哈尔滨工程大学 ， 应用化学， 2009， 硕士

【摘要】 Mg-Li系合金具有低密度、高比强度、高比刚度、阻尼性能好以及抗高能粒子穿透能力强等一系列优点,因而在航空航天、电子工业及通讯行业备受关注,以前所未有的速度向前发展。然而二元Mg-Li合金由于强度较低、抗腐蚀能力差在应用上受到很大的限制。加入稀土元素能显著提高Mg-Li合金的高温强度和抗蠕变性能。Mg-Li-RE合金的制备一般采用对掺法,该法是先制备金属镁、金属锂和稀土,之后将金属镁、金属锂和稀土混合,但该法存在着诸如流程长、金属锂和稀土的严重偏析等缺点,鉴于对掺法的缺点,本文提出全部采用金属化合物为原料,通过熔盐电解共电沉积一步直接制备Mg-Li-RE合金的新方法。本论文在620℃的LiCl-KCl-MgCl2-HoCl3-(KF)熔盐体系中采用熔盐电解共电沉积制备Mg-Li-Ho合金,研究了金属锂、镁和钬的电沉积过程,并对Mg-Li-Ho合金的电解工艺进行优化,研究合金成分可控性；并进一步探讨稀土钬对Mg-Li合金组织结构和性能的影响。采用循环伏安法在LiCl-KCl-MgCl2-HoCl3熔盐体系中研究Li+、Mg2+和Ho3+分别在钼电极的电化学还原过程。研究结果表明,在熔盐体系的温度为620℃时,金属Li和Ho的欠电位沉积发生在预先沉积在钼电极的二次Mg电极上,形成富含钬的a(Mg)固熔体合金和包含α(Mg)、β(Li)和Mg2Ho相的液态Mg-Li-Ho合金。在低温620℃熔盐LiCl-KCl-MgCl2-HoCl3-KF体系中制备Mg-Li-Ho合金,研究了电流密度、电解温度和电解时间等电解工艺参数,优化了低温条件下制备镁锂钬合金的最佳工艺条件,并通过控制电解时间及稀土Ho添加量制备α、α+β和β等不同相组成的Mg-Li-Ho合金。研究了稀土Ho在Mg-1.9Li基合金中的作用及机理,结果表明：Ho分布在α(Mg)和α(Mg)晶粒周围,对α(Mg)细化、球化作用明显。适量的Ho对Mg-1.9Li合金具有固溶强化作用,Mg-1.9Li-xHo系合金随Ho含量的增加,硬度增加。研究了稀土Ho在Mg-6.6Li基合金中的作用及机理,结果表明：稀土Ho对α(Mg)有细化、球化作用。适量的Ho对Mg-6.6Li合金具有固溶强化作用,Mg-6.6Li-xHo系合金随Ho含量的增加,硬度增加。研究了稀土Ho在Mg-9.7Li基合金中的作用及机理,结果表明：Ho在Mg-9.7Li合金中,Ho既对Mg-9.7Li合金有细化作用又有固溶强化作用,同时有弥散化合物HoMg2产生,硬度也随Ho含量增加而增大,抗腐蚀性也有所提高。研究了稀土Ho在Mg-11.9Li基合金中的作用及机理,结果表明：Ho在Mg-11.9Li合金中固溶较小,对其有较好的细化效果,硬度的增加与HoMg2的析出有关。更多还原

【Abstract】 The application for Mg-Li alloys in the aircraft, electronics and communication industries has been expanding at a high rate due to their low density, high strength-to-weigh, rigidity-to-weigh ratio, good damping capacity and good electromagnetic shielding properties. However their commercial application has been limited because of low strength and poor corrosion resistance. Added the rare earth elements to magnesium alloy can significantly increase the high temperature strength and anti-creep capacity. Traditional producing methods of Mg-Li-RE as added into the alloy diretly, which have prepared Mg, Li and Ho before producting Mg-Li-RE alloys. This have many disadvantages such as long flow, high energy cost and the severe deflection of Li and RE.In this study, we bring forward"melting salt electrolysis method"to produce Mg-Li-RE alloy.In this thesis, the Mg-Li-Ho alloys were prepared through electro-codeposition method in a molten LiCl-KCl-MgCl2-HoCl3-(KF) system at 620℃. The electrodeposition mechanism of Mg, Li and Ho as well as the formation process of Mg-Li-Ho alloys were both studied. The electrolysis process parameters of Mg-Li-Ho alloys and effect of holmium on microstructure and mechanical properties of Mg-Li alloy were also investigated.The electrochemical behaviour of Mg2+, Li+and Ho3+were studied at the molybdenum electrodes in the molten LiCl-KCl-MgCl2-HoCl3. Cyclic voltammetry was used in order to explore the deposition mechanism of Mg, Li and Ho. The results showed that the electroreduction of Li+, Mg2+and Ho3+ proceeds via a single step at 620℃. The underpotential deposition of lithium and holmium on pre-deposited magnesium leads to the formation of liquid Mg-Li-Ho alloys, which include aMg,βLi and Mg2Ho.Mg-Li-Ho alloys was prepared in the molten LiCl-KCl-MgCl2-HoCl3-KF electrolyte at 620℃.The electrolysis process parameters such as current density, temperature and electrolysis time were optimized. Preparingα,α+βandβMg-Li-Ho alloys by controlling time and Ho contentIn the research about the effects and mechanisms of Ho in Mg-1.9Li alloys, the results show that, Ho was distributed a(Mg) and theα(Mg) grain boundaries. Meanwhile, Ho has the good effects of refinement and spheroidization on the a(Mg) phase, The suitable Ho content in Mg-1.9Li alloy has the effects of solid-solution strenghen, With the increase of Ho content, the hardness increase.In the research about the effects and mechanisms of Ho in Mg-6.6Li alloys, the results show that, Ho has also the effects of refinement and spheroidization on the a(Mg) phase, The suitable Ho content in Mg-6.6Li alloy has the effects of solid-solution strenghen, With the increase of Ho content, the hardness increase.In the research about the effects and mechanisms of Ho in Mg-9.7Li alloys, the results show that, The suitable Ho content in Mg-9.7Li alloy has the effects of solid-solution strenghen, refinement strenghen and the second-phase HoMg2 strenghen. With the increase of Ho content, the hardness increase and the corrosion resistance of the alloy is improved.In the research about the effects and mechanisms of Ho in Mg-11.9Li alloys, the results show that, Ho in the Mg-11.9Li alloy exists in the form of HoMg2. Adequate Ho content has the effects of refining and secondary-phase HoMg2 strengthening for alloys更多还原