混合稀土（Ce-La-Nd-Pr）对Mg-4AI合金铸造流动性及组织性能的影响

发布时间：2018-03-11 22:11

本文选题：Mg-4Al合金　切入点：混合稀土　出处：《长春工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：面对日益严峻的能源危机以及人们对良好的生活环境的迫切需求,作为常用金属结构材料中最轻的镁合金的实际需要迅速增加,对其具有良好性能的期望也与日俱增。实际生产中,Mg-4Al合金是目前用途较广的铸造镁合金,组织中的β-Mg17Al12相以及浇注过程熔液产生的氧化杂物是影响其铸造流动性的关键因素,限制了其在需要良好充型能力汽车配件的产品或其它精密器件中的应用。本文以添加混合稀土(Ce-La-Nd-Pr)后的Mg-4Al-RE为研究对象,参照未处理的Mg-4Al合金,利用三螺旋砂型模具,研究和探讨了混合稀土的添加对Mg-4Al的铸造流动性及其组织性能的影响；另一方面,利用砂型阶梯模具,研究了冷却速度对Mg-4Al-RE合金的组织和性能影响；通过电化学实验的塔菲尔线外推法,来表征混合稀土RE对Mg-4Al合金耐腐蚀性能的影响,实验结果显示,在Mg-4Al中添加混合稀土,能够使该合金的铸造流动长度平均提高1/3(最高增加45.7%,最低增加16%)。RE优先与镁合金熔体里Mn元素反应,并形成中间相,以上中间相的生成可细化其的铸态组织,有效的抑制了β-Mg17Al12相的形成。本论文中,稀土元素形成Al11Ce3、 Al11La3和Al10(Ce,La)2Mn7相促进了形核率,产生析出强化,提升Mg-4Al硬度和耐蚀性。增加冷却速度,可细化晶粒,进而提高Mg-4Al合金的硬度及其耐蚀性。因此,添加混合稀土(Ce-La-Nd-Pr)可以有效的提高Mg-4Al合金的铸造流动性能和耐蚀性能。增加冷却速度,有助于细化Mg-4Al的晶粒,并提升其腐蚀性能和硬度。
[Abstract]:In the face of the increasingly severe energy crisis and the urgent need for a good living environment, the actual needs of magnesium alloys, which are the lightest of the commonly used metal structural materials, have increased rapidly. The expectation of its good properties is also increasing. Mg-4Al alloy is a widely used cast magnesium alloy in actual production. The 尾 -Mg17Al12 phase in the microstructure and the oxidized debris produced by the molten solution in the casting process are the key factors affecting the casting fluidity of the alloy. It limits its application in products or other precision devices that require good filling capacity. In this paper, the Mg-4Al-RE after adding mixed rare earth elements (Ce-La-Nd-Pr) is taken as the research object, referring to the untreated Mg-4Al alloy, the three-helix sand mould is used. The effect of mixed rare earth addition on the casting fluidity, microstructure and properties of Mg-4Al was studied, on the other hand, the effect of cooling rate on the microstructure and properties of Mg-4Al-RE alloy was studied by using the sand die. The effect of RE on the corrosion resistance of Mg-4Al alloy was characterized by the Taffer line extrapolation method of electrochemical experiments. The experimental results showed that the mixed rare earth elements were added to Mg-4Al. The casting flow length of the alloy can be increased by an average of 1 / 3 (the maximum increase is 45.7, and the lowest increase is 16%). RE preferentially reacts with mn element in the magnesium alloy melt and forms the mesophase. The formation of the above mesophase can refine the as-cast structure of the alloy. The formation of 尾 -Mg17Al12 phase was effectively inhibited. In this thesis, the formation of rare earth elements Al11Ce3, Al11La3 and Al10Ce La-2Mn7 promoted nucleation rate, precipitated strengthening, enhanced hardness and corrosion resistance of Mg-4Al, increased cooling rate, and refined grains. Therefore, the casting fluidity and corrosion resistance of Mg-4Al alloy can be improved effectively by adding mixed rare earth elements Ce-La-Nd-Pr. the cooling rate is increased and the grain size of Mg-4Al can be refined. And improve its corrosion performance and hardness.
【学位授予单位】：长春工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.22;TG292

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