本文選題：稀土變形鎂合金 + 稀土氧化物��； 參考：《吉林大學(xué)》2016年博士論文

【摘要】：稀土變形鎂合金的制備一般采用添加鎂-稀土中間合金的方法,因此需要對稀土資源進(jìn)行提純,在這一過程中產(chǎn)生的氟化物等有毒物質(zhì)對環(huán)境的污染十分嚴(yán)重。而稀土氧化物既是稀土的自然存在形式,又是制備稀土金屬和鎂-稀土中間合金的前置產(chǎn)物,提純?nèi)菀浊沂袌鰞r(jià)格十分低廉。因此稀土氧化物直接還原制備稀土變形鎂合金可以減少稀土提純和中間合金的制備,減輕有毒產(chǎn)物對環(huán)境的危害,降低稀土變形鎂合金的制造成本。本文選用AZ31鎂合金為研究載體,按預(yù)先設(shè)計(jì)的正交方案,研究稀土氧化物直接還原制備含稀土AZ31鎂合金,確定了不同參數(shù)下稀土氧化物的還原率。深入探討了稀土氧化物還原反應(yīng)的熱力學(xué)原理及影響稀土氧化物還原率的動力學(xué)因素。比較了稀土氧化物還原制備的含稀土AZ31合金與采用鎂-稀土中間合金制備的相同稀土含量的AZ31合金的組織、抗拉強(qiáng)度、軋制變形能力和抗氧化性,并得到了如下結(jié)論:(1)進(jìn)行了單一CeO_2和La_2O_3及混合稀土氧化物還原制備含稀土AZ31合金的研究,確定了不同參數(shù)下單一CeO_2的還原率最高可達(dá)11.50%,單一La_2O_3的還原率最高可達(dá)26.85%;混合稀土氧化物中CeO_2的最大還原率為9.45%,La_2O_3的最大還原率為21.08%。(2)單一CeO_2的還原反應(yīng)主要以2Mg+CeO_2=Ce+2MgO為主。單一La_2O_3的還原反應(yīng)主要有三種,分別為:a.先發(fā)生反應(yīng):La_2O_3+3CaF_2=2LaF_3+3Ca O,之后進(jìn)行還原反應(yīng):LaF_3+Mg=La+M F_2;b.先發(fā)生絡(luò)合反應(yīng):(La_2O_3)+(F~-)→(LaOF)n~(x-)),之后與Al進(jìn)行還原反應(yīng):(LaOF)n~(x-))+[Al]→[La]+(AlF_6~(3-))or(Al OF);c.先發(fā)生反應(yīng):La_2O_3+3Mg Cl_2=2LaCl_3+3MgO,之后發(fā)生電解:LaCl_3(?) La+Cl_2.�；旌舷⊥裂趸锏倪�原按CeO_2和La_2O_3的還原分別進(jìn)行,二者之間不發(fā)生交互反應(yīng)。(3)影響稀土氧化物還原率的正交因素最優(yōu)水平分析表明:稀土氧化物的添加量攪拌時(shí)間與稀土氧化物的還原率呈正比,而最佳熔煉溫度為710℃。影響單一CeO_2和La_2O_3還原率的最主要因素為攪拌時(shí)間,影響混合稀土氧化物還原率的最主要因素為稀土氧化物添加量。按最小二乘法計(jì)算得到關(guān)于AZ31合金中稀土含量與稀土氧化物添加量、攪拌時(shí)間之間的回歸方程。對單一CeO_2有:Φ_(Ce_=0.093x+0.067y-2.87;對單一La_2O_3有:Φ_(La)=0.24x+0.068y-2.97;對混合稀土氧化物中的CeO_2和La_2O_3分別有:Φ_(Ce)=0.084x+0.001y-0.341和Φ_(La)=0.61x+0.041y-5.698。其中Φ_(Ce)和Φ_(La)為AZ31合金中的Ce和La的含量,x為稀土氧化物的添加量,y為攪拌時(shí)間。(4)實(shí)驗(yàn)表明,稀土氧化物還原制備的AZ31合金隨稀土含量增加,其晶粒尺寸減小,抗拉強(qiáng)度、軋制變形能力和抗氧化性提高。但當(dāng)稀土含量增加至一極值時(shí),晶粒尺寸開始增加,各項(xiàng)性能呈下降趨勢變化。與采用鎂-稀土中間合金制備的AZ31合金相比較,二者在稀土含量相同時(shí)其組織及性能基本相近,因此還原法制備的含稀土AZ31合金具有可替代性。
[Abstract]:Rare earth wrought magnesium alloys are usually prepared by adding magnesium-rare earth master alloys, so it is necessary to purify rare earth resources. The toxic substances such as fluoride produced in this process pollute the environment very seriously. Rare earth oxides are not only the natural forms of rare earths but also the preproducts of preparing rare earth metals and Mg-rare earth master alloys. It is easy to purify and the market price is very low. So the preparation of rare-earth wrought magnesium alloys by direct reduction of rare earth oxides can reduce the purification of rare earths and the preparation of master alloys, reduce the harm of toxic products to the environment, and reduce the manufacturing cost of rare-earth wrought magnesium alloys. In this paper, AZ31 magnesium alloy was selected as the carrier to study the preparation of rare earth containing AZ31 magnesium alloy by direct reduction of rare earth oxide according to the orthogonal scheme designed in advance. The reduction rate of rare earth oxide under different parameters was determined. The thermodynamic principle of rare earth oxide reduction reaction and the kinetic factors affecting the reduction rate of rare earth oxide were discussed. The microstructure, tensile strength, rolling deformation and oxidation resistance of rare earth AZ31 alloy prepared by rare earth oxide reduction and AZ31 alloy with the same rare earth content prepared by magnesium rare earth master alloy were compared. The following conclusions have been obtained: (1) the preparation of rare earth containing AZ31 alloy by single CeO_2 and La_2O_3 and mixed rare earth oxide reduction has been studied. The maximum reduction rate of single CeO_2 is 11.50, that of single La_2O_3 is 26.85, that of CeO_2 in mixed rare earth oxides is 9.45%. The maximum reduction rate of CeO_2 is 21.08% and 21.08% respectively. The main reduction rate of single CeO_2 is 2Mg CeO_2=Ce 2MgO. There are three kinds of reduction reactions of a single La_2O_3, which are respectively: a. There was a reaction of: La _ 2O _ 3 3CaF_2=2LaF_3 3Ca O, and then a reduction reaction: Laf _ 3 Mg=La M _ T _ 2b. First, there is a complexation reaction: 1 / L / L _ 2O _ 3 / F ~ (-) / A / O / F / N / C / C / L / L / L / L / L / L / T / L / L / L / L / L / L / L / L / L / L / L / C / L / L / L / L / C / L / L / L / L / L / L / L / C / L / O / O / C / Al / O / O / C First there was a reaction: La2O3 3Mg Cl_2=2LaCl_3 3MgO, and then there was an electrolytic reaction: LaCl3. La Cl_2.. The reduction of mixed rare earth oxides was carried out according to the reduction of CeO_2 and La_2O_3 respectively. The optimum level analysis of orthogonal factors affecting the reduction rate of rare earth oxides shows that the mixing time of rare earth oxides is proportional to the reduction rate of rare earth oxides, and the optimum melting temperature is 710 鈩，

本文編號：1904323