本文選題：Nd-Fe-B + 熱壓/熱流變��； 參考：《鋼鐵研究總院》2017年碩士論文

【摘要】：熱壓/熱流變工藝是制備全密度和納米晶各向異性釹鐵硼永磁材料的有效方法。并且利用熱流變釹鐵硼磁體沿著壓力方向取向的特點(diǎn),可以制備輻向永磁環(huán)。但是納米晶磁體的矯頑力并不高,未能達(dá)到理論的預(yù)期值,若要更進(jìn)一步擴(kuò)大熱流變釹鐵硼永磁體的應(yīng)用范圍,需要對(duì)熱流變磁體的矯頑力機(jī)理及增強(qiáng)矯頑力的方法進(jìn)行研究與探索。本文通過(guò)調(diào)整熱流變過(guò)程的流變溫度、流變速率等工藝參數(shù),并將Nd-Fe-B與Pr-Cu混合粉末進(jìn)行熱壓/熱流變處理,以對(duì)磁體的制備工藝及矯頑力的機(jī)制進(jìn)行研究。同時(shí),通過(guò)改善反向擠壓工藝,最終制備了無(wú)裂紋的各向異性釹鐵硼輻向永磁環(huán)。全文主要結(jié)論如下:(1)熱流變塊狀磁體的磁性能隨著流變速率的增加呈現(xiàn)先增加后減小的趨勢(shì),并在流變速率為0.0050s-1時(shí)達(dá)到最優(yōu)性能。SEM觀察表明,晶粒在流變速率為0.0050s-1時(shí)排布最為規(guī)整。XRD圖譜及沿不同方向的磁化曲線都表明塊狀磁體在流變速率為0.0050s-1時(shí)取向度最好。(2)少量添加Pr-Cu后,磁體的矯頑力提升效果明顯。通過(guò)對(duì)微觀結(jié)構(gòu)TEM的觀察,發(fā)現(xiàn)添加Pr-Cu后,主相片狀晶粒間的富稀土層變厚,晶粒尺寸變小,并有Pr-Cu富集現(xiàn)象。通過(guò)測(cè)量外加磁場(chǎng)與磁體的c軸呈不同夾角時(shí)的磁滯回線,發(fā)現(xiàn)熱流變釹鐵硼磁體的矯頑力機(jī)制由形核機(jī)制及釘扎機(jī)制共同作用,并且在添加Pr-Cu后,形核機(jī)制增強(qiáng),釘扎機(jī)制減弱。(3)通過(guò)調(diào)整反向擠壓工藝,最終制備了厚壁且無(wú)裂紋的輻向磁環(huán)。分析了輻向磁環(huán)的不均勻性的原因,認(rèn)為輻向磁環(huán)的不均勻性可通過(guò)模具設(shè)計(jì)等一系列方法來(lái)加以改進(jìn)。從磁環(huán)的頂部(上端)到底部(下端)位置,磁性能先增加后減小,并在距離磁環(huán)頂部為總高度3/4的位置,磁性能達(dá)到最高。擠壓速率從1.33mm/s變化至1.03mm/s的過(guò)程,在磁環(huán)的相同位置,磁性能都增大。擠壓速率為1.03mm/s時(shí),在距離磁環(huán)頂部為總高度3/4的位置時(shí),磁性能為Br=12.83 kGs,Hcj=16.39kOe,(BH)max=36.09MGOe。SEM 顯示,擠壓速率高時(shí),磁體晶粒排布混亂,不規(guī)則;擠壓速率低時(shí),晶粒排布更為規(guī)則。(4)磁環(huán)沿著直徑(磁環(huán)外表面至內(nèi)表面)方向,越靠近內(nèi)表面,矯頑力越低,剩磁越高,SEM顯示,在貼近內(nèi)表面位置,磁體晶粒排布更為規(guī)則,在貼近外表面,晶粒排布較為混亂。
[Abstract]:Hot pressing / thermal rheological process is an effective method for preparing NdFeB magnets with full density and nanocrystalline anisotropy. The radial permanent magnetic rings can be prepared by using the heat flux NdFeB magnets along the direction of pressure orientation. However, the coercivity of nanocrystalline magnets is not high and fails to reach the expected theoretical value. If we want to further expand the application scope of Nd-Fe-B permanent magnets with heat flux, The coercivity mechanism and the methods to enhance the coercivity of heat flux magnets need to be studied and explored. In this paper, the preparation process and coercivity mechanism of magnets were studied by adjusting the rheological temperature and rheological rate of the heat rheological process, and the mixture of Nd-Fe-B and Pr-Cu powder was treated by hot pressing / hot rheological treatment. At the same time, the crack free anisotropic NdFeB radial permanent magnetic ring was prepared by improving the reverse extrusion process. The main conclusions of this paper are as follows: (1) the magnetic properties of the heat flux bulk magnets increase first and then decrease with the increase of rheological rate, and the optimum properties are obtained when the rheological rate is 0.0050s-1. When the grain flow rate is 0.0050s-1, the most regular .XRD pattern and the magnetization curves along different directions show that the coercivity enhancement effect of bulk magnets is obvious after adding a small amount of Pr-Cu to the bulk magnets with the best orientation when the rheological rate is 0.0050s-1. By observing the microstructure of TEM, it is found that after the addition of Pr-Cu, the rare-earth rich layer between the main photo grains becomes thicker, the grain size becomes smaller and the Pr-Cu is enriched. By measuring the hysteresis loop of the magnetic field at different angles to the c axis of the magnet, it is found that the coercivity mechanism of the heat flux NdFeB magnets is combined with nucleation mechanism and pinning mechanism, and the nucleation mechanism is enhanced after the addition of Pr-Cu. By adjusting the reverse extrusion process, the radial magnetic ring with thick wall and no crack was finally prepared by adjusting the pinning mechanism. The reasons for the inhomogeneity of the radial magnetic ring are analyzed. It is considered that the inhomogeneity of the radial magnetic ring can be improved by a series of methods such as die design and so on. From the top (top end) to the bottom (bottom end) position of the magnetic ring, the magnetic performance first increases and then decreases, and the magnetic performance reaches the highest when the total height is 3 / 4 from the top of the ring. When the extrusion rate changes from 1.33mm/s to 1.03mm/s, the magnetic properties increase at the same position of the magnetic ring. When the extrusion rate is 1.03mm/s, when the total height is 3 / 4 from the top of the magnetic ring, the magnetic property is Br=12.83 kGsSU Hcjn 16.39kOeOEN (Br=12.83) 36.09MGOe.SEM shows that, when the extrusion rate is high, the distribution of the magnets is chaotic and irregular, and when the extrusion rate is low, the magnetic properties of the magnets are irregular, and the results show that when the extrusion rate is high, the magnetic properties of the magnets are irregular. The closer the inner surface, the lower the coercivity, and the higher the remanence, the more regular the distribution of the magnets is, and the closer the outer surface, the more regular the distribution of the magnets is, and the more regular the magnetic grains are, the more regular the magnetic grains are in the direction of the diameter (outer surface to the inner surface) of the magnetic ring, and the lower the coercive force is, the higher the remanence is, The grain distribution is more chaotic.
【學(xué)位授予單位】：鋼鐵研究總院
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM273

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