本文選題：晶界添加MgO　切入點(diǎn)：優(yōu)化晶界顯微組織　出處：《太原科技大學(xué)》2014年碩士論文

【摘要】：釹鐵硼永磁材料應(yīng)用于我國的各個領(lǐng)域，大到我國的航天工程，小到人們的日常生活，隨著更多基于釹鐵硼功能器件的開發(fā)，將會有更多的商品出現(xiàn)在我們周圍。我國稀土資源儲備豐富，釹鐵硼產(chǎn)業(yè)有很好的基礎(chǔ)，發(fā)展前途光明。但是目前我國釹鐵硼產(chǎn)業(yè)的自主知識產(chǎn)權(quán)還比較少，高端產(chǎn)品落于美國和日本，加大對它的研究勢在必行。 本文制備的磁體在真空燒結(jié)爐內(nèi)燒結(jié)而成，與雙合金法相似，基體的成分為：(PrNd)30Gd3Al0.8B1.03Fe余。在真空手套箱里將MgO按不同比例與制備的基體磁粉混合，并用球磨機(jī)球磨，然后將混合粉壓制成圓柱形并磁化，采用制定的燒結(jié)工藝在真空燒結(jié)爐中燒結(jié)。用NIM-10000H磁性能測量裝置測試各個樣品的磁性能、用高溫高壓反應(yīng)釜和CS電化學(xué)工作站測試各個樣品在濕熱和電化學(xué)環(huán)境中的的耐腐蝕性。通過XRD、SEM、EDS分析手段系統(tǒng)的研究MgO的添加對磁體的晶界相成份、晶界顯微組織的影響，找到磁性能與它們之間的內(nèi)在聯(lián)系。 研究結(jié)果表明：適量的MgO摻入可以使NdFeB合金磁性能和耐腐蝕性能在原有的基礎(chǔ)上有所提高。添加0.2%MgO時磁體的密度較原來增加了0.527g·cm-3，剩磁較原來增加了0.179T，磁能積增加了74KJ·m-3，過量則會導(dǎo)致磁性能逐漸降低，添加1%、1.2%MgO時磁體出現(xiàn)了燒結(jié)不完全現(xiàn)象，有大量微小孔隙。添加0.4%MgO磁體矯頑力最大，矯頑力相比于沒有添加MgO的磁體，增加了120KA·m-1。磁體的失重量則與之不同，在腐蝕24h時，未添加MgO的磁體腐蝕失重最小，添加0.2%MgO磁體腐蝕失重最大，腐蝕時間為48h時，添加0.4%MgO的磁體失重量最小，比未添加的磁體降低了6.2mg·cm-2，這說明腐蝕時間的對腐蝕有較大影響。 通過XRD分析，添加0.2%MgO的磁體主晶粒(006)晶向晶粒發(fā)育良好，晶粒取向度較好。通過SEM觀察材料顯微組織發(fā)現(xiàn)，添加MgO磁體中有新相的生成，對磁疇有強(qiáng)烈的釘扎作用，利于于矯頑力的提高；添加0.4%MgO磁體晶界明朗，有薄層富釹相，主晶粒細(xì)化。通過EDS發(fā)現(xiàn)添加的MgO僅存在于晶界相當(dāng)中，沒有進(jìn)入主相，富釹相的氧含量隨MgO的添加而逐漸增大，富釹相結(jié)構(gòu)也發(fā)生了的轉(zhuǎn)變。適量添加可以細(xì)化主相晶粒，防止大晶粒的產(chǎn)生，優(yōu)化了晶粒生長取向和晶界相，增加了磁粉的濕潤性提高了磁體密度，這是材料磁性能增強(qiáng)的主要原因，而過量添加，則會導(dǎo)致相反的效果，如添加1%、1.5%的MgO。通過高溫高壓加速氧化實(shí)驗和電化學(xué)腐蝕實(shí)驗，我們用磁體的失重量和電極化曲線的電極位表征磁體的抗腐蝕性，實(shí)驗數(shù)據(jù)結(jié)果表明，MgO的添加增強(qiáng)了磁體在電化學(xué)環(huán)境中的耐腐蝕性，，不僅提高了磁腐蝕電位，降低了腐蝕電流密度而且還保護(hù)了磁體原有的鈍化膜；失重實(shí)驗也表明適量添加MgO增強(qiáng)了磁體在濕熱環(huán)境下的抗腐蝕性能，從顯微組織觀察到磁體的腐蝕坑明顯減少，生成了化學(xué)性質(zhì)穩(wěn)定的化合物，隔斷了腐蝕介質(zhì)的擴(kuò)散，這對晶界穩(wěn)定大有裨益。
[Abstract]:NdFeB permanent magnetic materials are applied in every field of our country, from the space engineering of our country to the daily life of people. With the development of more NdFeB functional devices, more commodities will appear around us.China is rich in rare earth resources, NdFeB industry has a good foundation, bright future.However, the independent intellectual property rights of NdFeB industry in China are still relatively small, high-end products fall behind in the United States and Japan, so it is imperative to increase the research on NdFeB industry.The magnets prepared in this paper are sintered in a vacuum sintering furnace, similar to the double alloy method. The composition of the matrix is more than 30 Gd3Al0.8B1.03Fe.In the vacuum glove box, the MgO was mixed with the prepared magnetic powder in different proportions, then the mixed powder was milled by ball mill, then pressed into a cylindrical shape and magnetized. The sintering process was established and sintered in the vacuum sintering furnace.The magnetic properties of each sample were tested by NIM-10000H magnetic property measuring device, and the corrosion resistance of each sample was tested by high temperature and high pressure reactor and CS electrochemical workstation.The effect of the addition of MgO on the grain boundary phase composition and grain boundary microstructure of magnets was systematically studied by means of XRDX SEMS-EDS analysis, and the intrinsic relationship between magnetic properties and them was found.The results show that the magnetic properties and corrosion resistance of NdFeB alloys can be improved by proper addition of MgO.The density of magnets increased 0.527g cm-3, the remanent magnets increased 0.179T, the magnetic energy product increased 74KJ m-3s, and the magnetic properties decreased gradually when the magnets were added with 0.2%MgO. The magnets were not sintered completely and there were a lot of tiny pores when the magnets were added with 0.2%MgO.The coercivity of the magnets added with 0.4%MgO was the largest, and the coercivity was increased by 120KA m -1 compared with the magnets without MgO.The weight loss of magnets is different from that of magnets. When the corrosion time is 24 h, the weight loss of magnets without MgO is the least, and that of magnets added with 0.2%MgO is the largest, and that of magnets added with 0.4%MgO is the smallest when the corrosion time is 48 h.The 6.2mg cm-2 is lower than that of the unadded magnets, which indicates that the corrosion time has a great influence on the corrosion.By XRD analysis, the main grain orientation of the magnets added with 0.2%MgO is well developed and the orientation degree of the grains is better.The microstructure of the material observed by SEM shows that the new phase is formed in the added MgO magnet, which has strong pinning effect on the magnetic domain, which is beneficial to the increase of the coercivity, and the crystal boundary of the added 0.4%MgO magnet is clear, there is a thin layer of neodymium rich phase, and the main grain is fine.It is found by EDS that the added MgO exists only in the grain boundary and does not enter the main phase. The oxygen content of the neodymium rich phase increases with the addition of MgO, and the structure of the neodymium rich phase also changes.The addition of proper amount can refine the main phase grain, prevent the production of large grain, optimize the grain growth orientation and grain boundary phase, increase the wettability of magnetic powder and increase the density of magnets, which is the main reason for the enhancement of the magnetic properties of the material.Will result in the opposite effect, such as adding 1% of MgO 1.5%.Through accelerated oxidation and electrochemical corrosion experiments at high temperature and high pressure, the corrosion resistance of magnets is characterized by the loss of weight of the magnets and the electrode position of the polarization curves.The experimental results show that the addition of MgO enhances the corrosion resistance of magnets in electrochemical environment, not only increases the magnetic corrosion potential, reduces the corrosion current density, but also protects the original passivation film of the magnets.The weightlessness experiment also showed that the proper addition of MgO enhanced the corrosion resistance of magnets in humid and hot environment. From the microstructure, the corrosion pits of the magnets were obviously reduced, resulting in the formation of compounds with stable chemical properties, which separated the diffusion of corrosion media.This is of great benefit to the stability of the grain boundary.
【學(xué)位授予單位】：太原科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM273

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 戴長松,吳宜勇,王殿龍,胡信國;稀土永磁材料釹-鐵-硼的化學(xué)鍍鎳[J];材料保護(hù);1997年07期

2 王建平;釹鐵硼稀土永磁材料及其研究進(jìn)展[J];材料工程;1996年03期

3 高汝偉,王標(biāo),劉漢強(qiáng),韓廣兵,白崗,孫艷,劉濤;高性能燒結(jié)釹鐵硼磁體的研究與開發(fā)(一)[J];磁性材料及器件;2004年06期

4 劉湘漣;周壽增;;Nd-Fe-B磁體燒結(jié)致密化過程與致密化機(jī)制[J];磁性材料及器件;2006年05期

5 羅陽;;全球NdFeB磁體產(chǎn)業(yè)變化與發(fā)展的25年[J];磁性材料及器件;2008年06期

6 謝發(fā)勤，馬宗躍;離子鍍鋁的Nd－Fe－B永磁體性能研究[J];磁性材料及器件;1995年01期

7 梁樹勇,李景宏,孫德成,陳風(fēng)華;采用新工藝生產(chǎn)高性能燒結(jié)NdFeB永磁[J];磁性材料及器件;1999年02期

8 謝發(fā)勤,郜濤,鄒光榮;NdFeB磁體組成相的電化學(xué)腐蝕行為[J];腐蝕科學(xué)與防護(hù)技術(shù);2002年05期

9 謝發(fā)勤,郜濤,馬宗耀,鄒光榮;NdFeB永磁合金電化學(xué)腐蝕行為研究[J];腐蝕與防護(hù);2001年09期

10 張建成,李衛(wèi),李岫梅,高汝偉;晶粒尺寸及取向?qū)︹S鐵硼磁體磁性能的影響[J];金屬功能材料;1999年01期

相關(guān)博士學(xué)位論文 前1條

1 崔熙貴;燒結(jié)Nd-Fe-B永磁材料顯微結(jié)構(gòu)優(yōu)化與性能研究[D];浙江大學(xué);2009年

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