本文選題：混合稀土　切入點(diǎn)：雙合金　出處：《中國科學(xué)院大學(xué)(中國科學(xué)院物理研究所)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：由于Nd相對低的豐度和高的價(jià)格,使用高豐度和低價(jià)格的La、Ce取代Nd-Fe-B中的部分Nd已經(jīng)成為近幾年稀土永磁材料研究的熱點(diǎn)之一�；旌舷⊥罬M(Mischmetal)是由La、Ce、Pr和Nd按一定比例組成的混合物,是稀土分離過程的中間產(chǎn)物。使用混合稀土取代Nd-Fe-B中的部分Nd,既有利于稀土的平衡和綜合利用又可以降低磁體的成本。本文制備并研究了混合稀土鐵硼、混合稀土鐵硼與釹鐵硼的多主相磁體,并對磁體的基本磁性能和顯微結(jié)構(gòu)等進(jìn)行了分析,主要得到以下結(jié)論:用電弧熔煉方法制備了MM_(14)Fe_(79.9)B_(6.1)(MM=La_(28.0)Ce_(52.0)Pr_(5.1)Nd_(14.7Sm0.20)合金,XRD精修得到樣品的主相為MM_2Fe_(14)B,其晶格常數(shù)a=8.780?,c=12.185?,計(jì)算出理論密度為ρ=7.589 g/cm3,均小于Nd-Fe-B的值。用傳統(tǒng)燒結(jié)方法制備了MM_(14)Fe_(79.9)B_(6.1)磁體,得到磁體的居里溫度約為210 oC,遠(yuǎn)小于Nd-Fe-B磁體的居里溫度。當(dāng)燒結(jié)溫度為1030 oC時(shí),磁體的密度為7.52 g/cm3。經(jīng)過900oC一級回火后,磁體的矯頑力Hcj和最大磁能積(BH)max都有了一定程度的提升。經(jīng)過1010 oC燒結(jié)和900 oC一級回火后,磁體的性能為Hcj=1.08 kOe和(BH)max=7.72 MGOe。當(dāng)燒結(jié)溫度達(dá)到1050 oC時(shí),磁體的晶粒顯著長大,磁性能急劇降低。通過EDS分析結(jié)果表明,La進(jìn)入了主相晶粒中,但進(jìn)入主相的La比混合稀土中La的比例少約7.5 at.%,這可能是由于La不容易形成2:14:1相的原因。用雙合金法制備了不同成分比例的MM_(14)Fe_(79.9)B_(6.1)/Nd_(13.5)Fe_(80.5)B_6多主相磁體。當(dāng)燒結(jié)溫度為1030 oC時(shí),磁體的密度為7.55 g/cm3。當(dāng)混合稀土MM含量占稀土R總量的值(MM/R)大于30.3 at.%時(shí),磁體具有兩個(gè)居里溫度Tc1和Tc2,其中Tc1對應(yīng)的是富LaCe主相的居里溫度,Tc2對應(yīng)的是富Nd主相的居里溫度。當(dāng)MM/R從30.3 at.%增加到50.6 at.%,Tc1則由276.5 oC下降到256.6 oC。磁體的Hcj和(BH)max隨混合稀土MM的增加而下降,當(dāng)MM/R=30.3 at.%,磁體的Hcj=7.11 kOe、(BH)max=41.0 MGOe。當(dāng)MM/R=50.6 at.%時(shí),磁體的Hcj=4.84kOe、(BH)max=34.0 MGOe。隨著混合稀土含量的增加,磁體主相晶粒中La、Ce、Pr和Nd分布的不均勻性增加,這種不均勻性使得晶粒內(nèi)部交換耦合作用增強(qiáng),有利于提高磁體的剩磁。對于多主相磁體,矯頑力機(jī)制為疇壁釘扎機(jī)制。通過微磁學(xué)模擬Ce2Fe14B/Nd_2Fe_(14)B磁體發(fā)現(xiàn),具有“核殼結(jié)構(gòu)”的磁體具有更高的矯頑力,但并不是“殼”的厚度越厚越好,因?yàn)椤皻ぁ焙穸鹊脑黾?會使磁體的不均勻性變差,降低磁體晶粒之間的長程靜磁相互作用,進(jìn)而導(dǎo)致矯頑力的下降。同樣用雙合金法制備了不同成分比例的MM_(14)Fe_(79.9)B_(6.1)/N45N45的成分大約為(Pr,Nd,Dy)30.5Febal(Al,Cu)0.7B1)多主相磁體。在直接二級回火處理時(shí),磁體的矯頑力隨著回火溫度的升高而有略微的下降。經(jīng)過一級回火和二級回火后的磁體的磁性能與直接進(jìn)行二級回火處理的磁體的性能基本相當(dāng)。因此,制備混合稀土鐵硼與釹鐵硼多主相磁體的過程中,可以不用一級回火處理,直接二級回火處理即可。MM/R約為30 at.%磁體的最佳磁性能為Br=13.22 kGs、Hcj=9.55 kOe、(BH)max=40.39 MGOe。
[Abstract]:Because of the abundance of Nd is relatively low and high prices, high abundance and low price La, Ce replace Nd in Nd-Fe-B has become one of the hot spots in recent years, rare earth permanent magnet materials research. Mixed rare earth MM (Mischmetal) is composed of La, Ce, Pr and Nd mixture according to a certain proportion, is the intermediate product of rare earth separation process. The use of mixed rare earth to replace part of the Nd Nd-Fe-B, is conducive to the balanced and comprehensive utilization of rare earth magnet and can reduce the cost. This paper prepared and studied the mixed rare earth iron boron, iron and boron mixed rare earth NdFeB magnets and the main magnetic properties of the magnet, the basic and microstructure were analyzed. The main conclusions are as follows: using arc melting method to prepare MM_ (14) Fe_ (79.9) B_ (6.1) (MM=La_ (28) Ce_ (52) Pr_ (5.1) Nd_ (14.7Sm0.20) alloy, XRD refinement to obtain the sample the main phase is MM_2Fe_ (14) B, the lattice constant of a= 8.780?, c=12.185?, to calculate the density of P =7.589 g/cm3, were less than the value of Nd-Fe-B. With the traditional sintering preparation method of MM_ (14) Fe_ (79.9) B_ (6.1) magnet, magnet can get the Curie temperature is about 210 oC, far less than the Curie temperature of Nd-Fe-B magnet. When the sintering temperature for 1030 oC, the magnet density is 7.52 g/cm3. after 900oC level after tempering, the coercivity of Hcj magnets and the maximum energy product (BH) of Max have a certain degree of improvement. After 1010 oC and 900 oC sintering level after tempering, the magnet performance for Hcj=1.08 kOe and max=7.72 MGOe. (BH) when the sintering temperature reaches 1050 oC, the magnet grains grow up, the magnetic properties decreased sharply. Through the analysis of EDS showed that La entered the main phase grain, but to enter the main phase of La is about 7.5 at.% less than La in rare earth mixture proportion, this may be because the La is not easy to cause the:1 2:14 using the double alloy method. 澶囦簡涓嶅悓鎴愬垎姣斾緥鐨凪M_(14)Fe_(79.9)B_(6.1)/Nd_(13.5)Fe_(80.5)B_6澶氫富鐩哥浣，

本文編號：1581740