本文選題：Mg-4Al合金　切入點：混合稀土　出處：《長春工業(yè)大學》2015年碩士論文　論文類型：學位論文

【摘要】：面對日益嚴峻的能源危機以及人們對良好的生活環(huán)境的迫切需求,作為常用金屬結(jié)構(gòu)材料中最輕的鎂合金的實際需要迅速增加,對其具有良好性能的期望也與日俱增。實際生產(chǎn)中,Mg-4Al合金是目前用途較廣的鑄造鎂合金,組織中的β-Mg17Al12相以及澆注過程熔液產(chǎn)生的氧化雜物是影響其鑄造流動性的關(guān)鍵因素,限制了其在需要良好充型能力汽車配件的產(chǎn)品或其它精密器件中的應(yīng)用。本文以添加混合稀土(Ce-La-Nd-Pr)后的Mg-4Al-RE為研究對象,參照未處理的Mg-4Al合金,利用三螺旋砂型模具,研究和探討了混合稀土的添加對Mg-4Al的鑄造流動性及其組織性能的影響；另一方面,利用砂型階梯模具,研究了冷卻速度對Mg-4Al-RE合金的組織和性能影響；通過電化學實驗的塔菲爾線外推法,來表征混合稀土RE對Mg-4Al合金耐腐蝕性能的影響,實驗結(jié)果顯示,在Mg-4Al中添加混合稀土,能夠使該合金的鑄造流動長度平均提高1/3(最高增加45.7%,最低增加16%)。RE優(yōu)先與鎂合金熔體里Mn元素反應(yīng),并形成中間相,以上中間相的生成可細化其的鑄態(tài)組織,有效的抑制了β-Mg17Al12相的形成。本論文中,稀土元素形成Al11Ce3、 Al11La3和Al10(Ce,La)2Mn7相促進了形核率,產(chǎn)生析出強化,提升Mg-4Al硬度和耐蝕性。增加冷卻速度,可細化晶粒,進而提高Mg-4Al合金的硬度及其耐蝕性。因此,添加混合稀土(Ce-La-Nd-Pr)可以有效的提高Mg-4Al合金的鑄造流動性能和耐蝕性能。增加冷卻速度,有助于細化Mg-4Al的晶粒,并提升其腐蝕性能和硬度。
[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.
【學位授予單位】：長春工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG146.22;TG292

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本文編號：1600132