High coercivity Nd-Ce-Fe-B nanostructured ribbons prepared from melt spinning technique

The Ce-substituted(Nd_(1-x)Ce_x)_(12.2) Fe_(81.6) B_(6.2)(x=0.0, 0.2, 0.4, 0.6) nanocrystalline ribbons were prepared by annealing amorphous ribbons from melt spinning. It is found that all ribbons are in a multiphase state consisting of a-Fe phase, Nd(Ce)-rich phases and RE_2 Fe_(14) B(RE = Nd, Ce) phases. However, the coercivity of all annealed ribbons can reach a considerably high value without doping any heavy rare earth or other coercivity enhanced elements. A strong intergranular exchange coupling appears in these nanocrystalline ribbons. The Nd_(12.2) Fe_(81.6) B_(6.2) ribbons with multiphase have a coercivity of about 11.3 k Oe, and the coercivity decreases slightly with increasing Ce content. A coercivity of 7.5 kOe can be obtained when60 at% of Nd is replaced by Ce(x = 0.6) due to the grain refinement and the strong intergranular exchange coupling. This provides a practical approach of fabricating high coercivity Ce-substituted Nd-Fe-B materials.     

Influence of Melt-Spinning Parameters on the Structure and Soft Magnetic Properties of (Fe0.65Co0.35)88Zr7B4Cu1 Alloy

Melt-spun ribbons of (Fe_0.65Co_0.35)₈₈Zr₇B₄Cu₁ alloy have been prepared at different wheel speeds, namely, 47, 39, 34, and 17 m/s, and subsequently annealed at 773 K (500 °C) under controlled atmosphere. Structural and soft magnetic properties have been evaluated using X-ray diffraction, differential scanning calorimetry, transmission electron microscopy, and vibrating sample magnetometer. The structure of as-spun ribbons changes from fully amorphous to partially amorphous/nanocrystalline to fully nanocrystalline (bcc α-Fe(Co) + Fe₂Zr) on decreasing the wheel speed. Annealing of amorphous ribbons leads to the precipitation of nanocrystalline bcc α-Fe(Co) phase. The Curie temperature (T _c ) of the amorphous phase is found to increase with decreasing wheel speed possibly due to the effect of exchange field penetration of nanocrystals present in the amorphous matrix. The saturation magnetization (4πM _s ) of as-spun ribbons having partially nanocrystalline bcc α-Fe(Co) phase is high as compared to the ribbons with completely amorphous phase, and it remains almost the same even after annealing. The lowest coercivity has been achieved in the ribbons that are fully amorphous, and the coercivity was found to increase with decreasing wheel speed.     

Effect of Multiple Alloying Elements on Microstructure and Magnetic Properties of Nanocomposite Nd2Fe14B／α-Fe Magnets

TheappearanceofnanocompositemagnetsbroketheremanencelimitpredictedbyStoner Wolhfarthmodethattheremanenceofisotropicmagnetwouldnotexceedhalfofitssaturationmagnetization[1] .Accord ingtoSkomski′scalculation[2 ] ,highmaximalenergyproduct (BH) maxof 80 0kJ·m-3 couldbeachievedinNd2 Fe14 B α FenanocompositewhentheaveragegrainsizeofNd2 Fe14 Bisrefinedtoabout 2 0nmandthatofα Fetoabout 10nm ,becauseoftheeffectofrema nenceenhancement (Mr Ms >0 .5 ) .Unfortunately ,thereported (BH) max(185kJ·…     

Microstructure and electrochemical properties of melt-spun Nd_(0.8)Mg_(0.2)(Ni_(0.8)Co_(0.2))_(3.8) hydrogen storage alloy

The effects of rapid solidification on the microstructure and electrochemical properties of Nd0.8Mg0.2(Ni0.8Co0.2)3.8 alloy were systematically investigated.The microstructure of alloys was characterized by scanning electron microscopy(SEM),X-ray diffractometer(XRD) and transmission electron microscopy(TEM).It was found that the melt-spun Nd0.8Mg0.2(Ni0.8Co0.2)3.8 ribbons became thinner and the average grain size of the ribbons became smaller with increasing wheel speed.A fraction of amorphous phase was observed for the ribbons melt-spun at high wheel speed(≥20 m/s).Microstructural characterization revealed that two phases:(Nd,Mg)2(Ni,Co)7 main phase(Ce2Ni7 type structure) and NdNi5 second phase(CaCu5 type structure),existed in the samples in cast state and melt-spun.The cycle stability of the melt-spun alloys was significantly enhanced as compared with cast alloy,and the sample prepared at wheel speed of 20 m/s exhibited good comprehensive electrochemical properties.     

纳米晶交换耦合稀土粘结永磁体磁性能与制备工艺参数间关系的研究

本文利用熔体快淬工艺将成分为Ｎｄ８．１６Ｄｙ１Ｆｅ８５．２６Ｎｂ１Ｂ４．５８的合金在三种不同淬速（１２．２５、１６．３３、２８．６ｍ／ｓ）下制备成非晶快淬条带,并在热处理后经快速淬火而制得纳米永磁体。利用ＴＥＭ和ＸＲＤ方法,对晶化后的稀土永磁粉进行了微结构分析与表征,初步探讨了淬速及晶化条件（包括晶化温度和时间）对稀土粘结永磁体磁性能的影响规律,获得了较高矫顽力的纳米交换耦合稀土粘结永磁体。     

An investigation of hydrogen storage kinetics of melt-spun nanocrystalline and amorphous MgeNi-type alloys

The nanocrystalline and amorphous Mg2Ni-type Mg2–xLaxNi (x=0,0.2) hydrogen storage alloys were synthesized by melt-spinning technique.The as-spun alloy ribbons were obtained.The microstructures of the as-spun ribbons were characterized by X-ray diffraction (XRD),high resolution transmission electronic microscopy (HRTEM) and electron diffraction (ED).The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus,and their electrochemical kinetics were tested by an automatic galvanostatic system.The electrochemical impedance spectrums (EIS) were plotted by an electrochemical workstation (PARSTAT 2273).The hydrogen diffusion coefficients in the alloys were calculated by virtue of potential-step method.The obtained results showed that no amorphous phase was detected in the as-spun La-free alloy,but the as-spun alloys substituted by La held a major amorphous phase,con-firming that the substitution of La for Mg markedly intensified the glass forming ability of the Mg2Ni-type alloy.The substitution of La for Mg notably improved the electrochemical hydrogen storage kinetics of the Mg2Ni-type alloy.Furthermore,the hydrogen storage kinetics of the experimental alloys was evidently ameliorated with the spinning rate growing.     

Investigation of Structure and Magnetic Properties of Rare Earth-Leaned Pr2(Fe,Co)14(C,B)-Type Nanocomposites

The phase evolution and magnetic properties of Pr_xFe_82-x-yTi_yCo₁₀B₄C₄ (x=9–10.5; y=0, 2) melt-spun ribbons have been investigated. The effects of wheel speed and annealing on the crystallization and magnetic properties of the ribbons were emphatically discussed. It was found that Ti substitution enhances the glass forming ability of the Pr₂(Fe,Co)₁₄(C,B)-type ribbons. For the high wheel speed V_s (18 m/s), the Ti-substitution ribbons consist of significant amorphous phase, and show a typical two-step magnetic behavior, while most of Ti-free ribbons are mainly composed of the crystallized 2:14:1, α-(Fe, Co) and 2:17 phases. With decrease in wheel speed, all these composition of ribbons are crystallized, and more magnetically hard 2:14:1 phase is formed in the ribbons. The content of metastable 2:17 phase in the ribbons decreases with increasing Pr and Ti substitution. A B_r of 9.5 kG, _iH_c of 9.8 kOe, and (BH)_max of 16.0 MGOe were obtained in the as-spun Ti-substitution Pr_10.5Fe_69.5Ti₂Co₁₀B₄C4 ribbon prepared at V_s=15 m/s. For all the as-spun Ti-free ribbons prepared at different wheel speed V_s, the (BH)_max is lower than 10 MGOe owing to poor demagnetization-curve shape. Ti substitution also helps suppressing the grain growth of 2:17 phase during annealing process, and simultaneously, gently promoting the growth of magnetically hard 2:14:1 phase. Annealing treatment significantly improves the magnetic properties of the Ti-substitution ribbons with higher Pr content. No obvious promotion of magnetic properties was found in the Ti-free ribbons after annealing.     

Y取代对Pr-Nd-Fe-B合金微观结构和磁性能的影响

基于熔体快淬技术，研究了不同Y取代量对[（Pr_0.25Nd_0.75）_1-xY_x]_13.9Fe_80.1B₆合金物相组成、磁性能、晶间磁相互作用和微观结构的影响.结果表明，适量Y替代Pr、Nd元素，可以抑制Fe₃B相的形成，且合金矫顽力温度稳定性增强.当Y取代Pr、Nd元素的量为30 %时，居里温度仅轻微从307 ℃下降至302 ℃. Y取代具有一定程度的晶粒细化作用，有助于改善合金的微观结构.此外，Y取代还可以增强主相晶粒间的交换耦合作用.      

Effect of high pressure on microstructure of crystallizing amorphous Nd9Fe85B6 alloy

The effect of high pressure on the microstructure of annealed amorphous Nd9Fe85B6 alloy was studied. It was found that application of high pressure made the microstructure of the crystallized alloy much more homogeneous. The average grain size of the Nd2Fe14B phase decreased with the increase of pressure, whereas, the size of the α-Fe first increased when a pressure of 1 GPa was applied and then decreased with further increase of pressure. Pressure-induced （410） texture of the Nd2Fe14B phase was also observed. The present study suggested an effective route for controlling the microstructure in a nanoscale solid.     

Microstructure,crystallization, and coercivity of rare earth-iron-boron amorphous alloy ribbons

Amorphous alloys of rare earth-iron-boron develop high coercivity when crystallized around 650 °C to 700 °C. These alloys are located in the iron-rich corner of the ternary system, and the alloys contain 10 to 15 at. pct rare earth (R). In the amorphous state, isomorphous substitution of different rare earth atoms occurs. The short-range Fe-Fe and R-Fe environments in amorphous ribbons are similar to those in Fe₃B and R₆Fe₂₃ (within 6 Å), respectively. Beyond 6 Å, the R-Fe environment appears similar to R₂Fe₁₄B. On nonisothermal heating of these alloy ribbons, a stress-relieving process occurs around 460 °C. The crystallization of α-Fe and R₂Fe₁₄B occurs at around 520 °C and near 600 °C, respectively. The Fe₃B and R₆Fe₂₃ phases crystallize next. Depending on the alloy composition, the Fe₃B crystallizes between 600 °C and 650 °C, and R₆Fe₂₃ crystallizes between 650 °C and 680 °C. The presence of rare earth atoms, 10 to 15 at. pct, significantly raises the crystallization temperatures of a-Fe and Fe₃B. The favorable short-range Fe-Fe and R-Fe environments may be responsible for the nucleation and growth (crystallization) of Fe₃B and R₆Fe₂₃ in the ternary alloys. The high coercivity of the annealed ribbons containing 10 at. pct Tb, Dy, and Ho is related to the single magnetic domain nature of the small crystallized grains of Fe₃B and R₆Fe₂₃. For the annealed alloy ribbons with 12 to 15 at. pct rare earth, the high coercivity is related to the ternary hard phase, R₂Fe₁₄B.     

Development of rapidly solidified 6.5 wt% silicon steel for magnetic applications

The 6.5wt% Silicon steel has always a technological importance owing to its soft magnetic properties and low core losses. In this research, this steel is prepared in the form of continuous ribbons of 25 mm width and 35 mm thickness by rapid solidification technique using melt spinner. The as-cast ribbons show single phase of α-FeSi as observed from x-ray diffraction. By transmission electron microscopy (TEM), the alloy shows disordered A2 structure in as-cast ribbon while B2 ordered phase forms from the A2 matrix at annealed condition. Two magnetization temperatures are observed at 670 and 760°C due to the phase transformation of B2 and A2 structures, respectively. The alloy showed enhancement in the soft magnetic properties with reduction in coercivity from 1.90Oe in the as-cast state to 0.58Oe when annealed at 850°C. The lowering of coercivity is due to the formation of ordered B2 phase during annealing.     

Constitution of melt-spun NdFeB-magnets studied by analytical field ion microscopy

An analytical field ion microscope was applied to melt-spun NdFeB magnets with various cobalt substitutions. The microstructure of melt-spun NdFeB magnets consists of three phases. Whereas the Nd₂Fe₁₄B- and the metastable Nd₇Fe₃-phase determine the magnetic properties of optimally quenched specimens the Nd_1.1Fe₄B₄-phase additionally influences the magnetic behaviour of overquenched and annealed material. With Co substitution the Nd-rich phase transforms via the metastable Nd₂₃(Fe_1−xCo_x)₇₅B₂ intermediate stage of optimally quenched specimens to the stable Nd(Fe_1−xCo_x)₂-phase in over-quenched and annealed ribbons. From our experimental data we conclude that a nucleation model of coercivity is consistent with the magnetic measurements.     

Big-data analysis of phase-formation rules in high-entropy alloys

Big-data analysis of phase-formation rules of high-entropy alloys (HEAs) was conducted and a phase for-mation rule from a dynamic view was deduced.It was indicated in literatures that cooling rate has a strong influence on the phase formation of HEAs.Higher cooling rate may promote the generation of amorphous phase, and accordingly suppress the formation of intermetallics.Meanwhile, it was also shown that cool-ing rate had little impact on the formation of solid-solution phase.To demonstrate this rule, a series of Fe-CoNi(AlSiB)x HEAs ribbons were fabricated by a melt-spinning technique, and the microstructure, me-chanical, and magnetic properties were also investigated.The results show that all ribbons exhibit disor-dered solid-solution structure.The addition of boron changes the alloy from ductility to brittleness, but without evident change of magnetic properties.The alloy in the nominal composition of FeCoNi(AlSi)0.2 has the best combination of mechanical and magnetic properties.A distinct feature of HEAs in magnetiza-tion was noticed and explained.     

Effects of cobalt addition on microstructure and magnetic properties of PrNdFeB/Fe_7Co_3 nanocomposite

The permanent magnetic nanocomposite PrNdFeB/Fe_7Co_3 ribbons were prepared by directly quenching, and the microstructure and magnetic influence of composite materials with Co substitution were studied. The phase identification and the magnetic properties were measured by X-ray diffraction(XRD) and vibrating sample magnetometry(VSM). Microstructure observation was performed using scanning electron microscopy(SEM). The crystallization temperatures of the hard magnetic phase and the soft magnetic phase were measured using differential scanning calorimetry(DSC). The experimental results showed that Co addition improved the Curie temperature of magnets. When the ribbons were melt-spun at 35 m/s, the added content of Co was 4 at.%, and the magnetic properties were the best, which were remanence(Br) of 0.379 T, coercivity(Hci) of 344.4 kA/m, the maximum magnetic energy product(BH)max of 32.6 kJ/m~3. Besides, the activation energy of each phase was calculated by Kissinger equation, which was 310.4 kJ/mol of Fe_7Co_3 phase and 510.2 kJ/mol of 2:14:1 phase, respectively.     

稀土钇对4.5％Si无取向硅钢成品板组织和磁性能的影响

采用4种不同稀土钇（Y）质量分数(0、0.006 %、0.012 %、0.016 %)的无取向4.5 %Si钢,探究了稀土Y对4.5 %Si钢成品板微观组织和磁性能的影响。研究表明,稀土Y可以将纳米级方形TiN、Al2O3夹杂物有效变质为球状TiO2、Al2O3、Y2O2S复合夹杂物,粗化夹杂物的尺寸,减少0~500 nm弥散细小的夹杂物的数量,因此添加适量Y可以使得4.5 %Si钢成品板晶粒长大速率加快,晶界迁移激活能减少,磁畴与晶界和夹杂物的相互作用的损耗减少,铁损降低。但过量Y会使细小夹杂物继续增多,晶界钉轧作用增强,成品板晶粒尺寸降低。在退火过程中,由于{111}取向晶粒易在微细夹杂物附近优先形核长大,稀土的添加降低了夹杂物密度,且稀土在晶界的富集减小了{111}晶粒在晶界的形核优势,因此稀土Y的添加削弱了γ织构的强度。结果表明,含0.012 %Y的试样的B50最高为1.655 T,在各频率下的铁损最低,分别为P1.0/50=1.41W/kg、P1.0/400=19.28 W/kg、P1.0/1000=77.69 W/kg。     

Mg-TM-Ln型镁基纳米结构材料研究

讨论了Mg-Cu-Y、Mg-Ni-Y和Mg-Zn-Y等三种重要的Mg-TM-Ln型的多组元Mg基纳米结构材料的成分构成、制备过程、微观结构和力学性能以及它们的形成机制。其中,制备方法涉及非晶部分晶化法、机械合金化/粉末冶金法(MA/PM法)和快速凝固(原子雾化)/粉末冶金法(RS/PM法)。结果表明,在Mg-Cu-Y系合金中,分布于非晶相基体之上的纳米晶体相使非晶合金的断裂应力增加。而不同成分的旋淬Mg-Cu-Y非晶条带弯曲断裂韧性的不同,很可能是由于存在于它们之中的纳米晶颗粒的性质有别而造成;在Mg-Ni-Y系合金中,Y部分地置换Ni将严重地影响其晶化行为,使得Mg-Ni-Y三元非晶合金中的纳米晶体相颗粒变得更加细小,而合金晶化行为的改变则导致了其杨氏模量的明显变化;在所有的金属合金中,RS/PMMg97Zn1Y2合金的比强度是最高的。而在所有的Mg基合金中,RS/PMMg-Zn-Y合金具有最佳的综合性能。     

Crystallization Kinetics of Pr_8Fe_(86-x)Zr_xB_6 Amorphous Alloys

Ｎａｎｏｃｏｍｐｏｓｉｔｅｍａｇｎｅｔｓ ,ｗｈｉｃｈｃｏｎｓｉｓｔｏｆａｔｗｏ ｐｈａｓｅｄｉｓｔｒｉｂｕｔｉｏｎｏｆｈａｒｄ ａｎｄｓｏｆｔ ｍａｇｎｅｔｉｃｇｒａｉｎｓ,ｈａｖｅａｔｔｒａｃｔｅｄｃｏｎｓｉｄｅｒａｂｌｅｉｎｔｅｒｅｓｔｓｓｉｎｃｅｔｈｅｙｃｏｕｌｄ ,ｂｙｅｘｃｈａｎｇｅｃｏｕｐｌｉｎｇ ,ｐｏｔｅｎｔｉａｌｌｙｐｒｏ ｖｉｄｅａｍａｘｉｍｕｍｅｎｅｒｇｙｐｒｏｄｕｃｔ ,(ＢＨ ) ｍａｘ,ｉｎｅｘ ｃｅｓｓｏｆ 10 0ＭＧＯｅ[1] ,ｗｈｉｃｈｉｓｍｕｃｈｌａｒｇｅｒｔｈａｎａｎｙｓｉｎｇｌ…     

Fe81Zr5Nb4B10非晶合金的晶化过程及其磁性研究

采用单辊快淬法制备Fe81Zr5Nb4B10非晶合金带,并在不同温度下对其进行退火处理,利用XRD和振动样品磁强计(VSM)测试了合金自由面和贴辊面的结构及磁性能。结果表明:随着退火温度的增加,淬态合金由完全的非晶态结构转变为非晶与纳米晶的混合结构,晶粒尺寸、晶化体积分数增大,晶粒间的非晶层厚度减小。和自由面相比,贴辊面的晶粒尺寸较大,晶化体积分数较小,晶粒间的非晶层厚度较大。合金的矫顽力和比饱和磁化强度σs随着退火温度的升高逐渐增大。     

射频磁控溅镀掺杂铜对钛酸锌薄膜中相变化及微结构的影响

探讨了ZnTiO₃薄膜掺杂Cu元素对于薄膜性质、相变化与微结构之影响.实验是在一定温度下以射频磁控溅镀系统将铜沉积于ZnTiO₃陶瓷靶上,控制沉积于ZnTiO₃陶瓷靶上铜含量之后,再沉积掺杂铜的钛酸锌薄膜于SiO₂/Si基板上.成长出来的薄膜经由ESCA分析得知铜的质量分数分别为0.84%、2.33%和2.84%.从XRD分析常温下掺杂Cu的ZnTiO₃薄膜为非晶质态,经过600℃退火后,ZnTiO₃薄膜则由非晶质态转变成Zn₂Ti₃O₈结晶相,而未掺杂铜的ZnTiO₃薄膜在600℃退火时并没有结晶相产生.ZnTiO₃薄膜经过900℃退火后,Zn₂Ti₃O₈相分解成Zn₂TiO₄相和TiO₂相,且ZnTiO₃晶格常数因为Cu离子置换至Zn离子的位置有变小的趋势.由TEM分析证实Cu离子与Zn离子的置换,导致晶格应变产生双晶缺陷.经由XRD、SEM和TEM分析得知掺杂太多的铜会抑制TiO₂相的生成,而随着过多的Cu析出,晶体平均晶粒慢慢变小晶格应变也随之降低,以致晶格常数回复往原来晶格常数方向趋近.      

Evolution of crystallographic alignment in Tb-Fe-B melt-spun ribbons

Ternary Tb-Fe-B ribbons were prepared via melt-spun technique under different wheel speeds of 5-25 m/s.Effect of wheel speed on the crystal structure and microstructure of the ribbons was investigated.All the ribbons quenched under different wheel speeds crystallized in single Tb2Fe14B phase with tetragon structure.Different crystallographic alignment evolutions were observed in the free side surface and wheel side surface of the ribbons.On the free-side surface,an in-plane c-axis crystal texture of Tb2Fe14B phase was found in the ribbons quenched at 5 m/s.However,with the increase in the wheel speed,the direction of the c-axis texture turns to perpendicular to the ribbon surface.On the wheel-side surface,a strong c-axis texture perpendicular to the ribbon surface was observed in the ribbons quenched at 5 m/s,and then weakened gradually with the increase in the wheel speed.Further investigation showed that the competition of the two types of temperature gradients during the quench process was responsible for the crystallographic alignment evolution in the ribbons.