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.     

Structural State and Magnetic Properties of Nd2Fe14B-Type Rapidly Quenched Alloys

Using the X-ray, elastic neutron diffraction (END) and small angular neutron scattering (SANS) methods (Diffractometers D2 and D3 respectively), transmitting electronic microscopy (JEOL JEM-200CX) and magnetometry technique (vibrating sample magnetometer - VSM) the structure and magnetic properties of the rapidly quenched (RQ) alloys of the following compositions: A) Nd₁₄Fe₇₈B₈; B) Y₁₂Fe₈₂B₆; C) Nd_13.3Co_6.6Fe_72.6Ge_0.9B_6.6; D)Nd₉Fe₈₅B₆; E) Nd₉Fe₇₉B₁₂; F) Nd₉Fe₇₄Ti₄CB₁₂ have been studied. At some quenching conditions or after consequent heat treatments of these alloys the nanoscale state of the main 2–14–1 phase and α-Fe grains can be formed. Their size depends on the sample-preparation conditions and lies in the interval of 10–200 nm. Their influence on magnetic properties of alloys under study is discussed.     

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·…     

Nd2Fe14B/α-Fe和Pr2Fe14B/α-Fe型纳米晶永磁合金工艺与性能的对比研究

对快淬法制备的Nd2Fe14B/α-Fe和Pr2Fe14B/α-Fe型双相纳米晶永磁在快淬条件和晶化过程中的软、硬磁相之间晶粒的形核长大行为作了对比,发现PrFeB系更容易得到较好磁性能。     

Effect of Gallium Addition on Magnetic Properties of Nd2Fe14B-Based/α-Fe Nanocomposite Magnets

The influence of Ga addition on the crystallization behavior and the magnetic properties of nanocomposite Nd2Fe14B-based/α-Fe magnets was investigated. It was found that the addition of 0.2% did not change the crystallization temperature of amorphous alloy, but the magnetic properties were improved significantly because of the strong exchange coupling interaction between the hard and soft magnetic phases. The optimum magnetic properties with iHc=600.3 kA·m-1, Br＝0.75 T, and (BH)max=88.03 kJ·m-3 were obtained in bonded Nd9.5(FeCoZr)83.8Ga0.2B6.5 magnet with 15 m·s-1 wheel speed and 670 ℃ annealing treatment. The apparent improvement of magnetic properties originates from the grain refinement calculated using the Scherrer formula from corresponding XRD patterns and the excellent rectangularity of the demagnetization curve.     

Effect of Heating Rate on Microstructure Evolution and Magnetic Properties of Cold Rolled Non-Oriented Electrical Steel

The effects of heating rate (ranging from 50 to 300 ℃/s) during the final annealing process on microstructure evolution and magnetic properties of cold rolled non-oriented electrical steel were investigated. It was found that increasing heating rate increased the nucleation temperature and complete recrystallization temperature. At the same time, heating rate increasing could cause the substantially refined structures for the recrystallization grains and this grain refinement would decline when the heating rate was beyond 50 ℃/s. The recrystallization texture exhibited pronounced improvement with heating rate, such as the intensity decrease of 111ND (normal direction) fiber and the intensity increase of {110}001 Goss texture component. The texture improvement and grain size refinement caused by heating rate increasing resulted in complicated variation of the magnetic properties. The magnetic induction (B50) keeps increasing while heating rate increases from 15 to 300 ℃/s which is due to the recrystallized texture optimization caused by rapid heating. The core losses (P1.5/50) decrease while heating rate increases from 15 to 100 ℃/s; however, the core losses would increase when heating rate is higher than 100 ℃/s, which is caused by the mean grain size refinement after rapid heating annealing. The results indicate that recrystallization texture and the magnetic properties of the non-oriented electrical steel can be improved definitely by rapid heating during the final annealing treatment.     

Nd2Fe14B/Fe3B基纳米复合粘结磁体的磁特性

通过实验研究了Nd2Fe14B／Fe3B双相纳米复合磁粉分别与几种不同性能的磁粉复合成粘结磁体后磁性能的变化。通过对复合磁体的理论分析得知，由Nd2Fe14B／Fe3B与RE2Fe14B或铁氧体磁粉复合成的粘结磁体中，成分间并未发生化学反应。以Nd2Fe14B／Fe3B铁氧体复合粘结磁体为例，根据理论分析推出的剩磁Br-成分含量关系曲线与实际曲线吻合得很好，表明剩磁与成分含量间存在着近似的线性关系，从而可通过数学手段建立磁性能参数与成分含量的函数关系式，用于简化混粉工艺。另外，添加铁氧体可对该复合磁体较差的热稳定性起到补偿作用，并减少了磁不可逆损失。     

液相扩散对钕铁硼磁体性能和组织结构的影响

用双合金工艺在Nd13.05Dy0.23Fe80.12B6.5铸片主合金中分别添加质量分数为3％～20％的富稀土铸锭辅合金Nd38.2Cc11.8Fe44.88Al4.12B,研究在钕铁硼永磁体中用Ce部分地取代Nd时对永磁体的磁性能的变化规律.实验结果表明,在一定的烧结及热处理工艺条件下,辅合金加入量介于8％ ～ 12％(质量分数)时,磁体的内禀矫顽力和磁能积相对较高,对剩磁的影响不大.显微成分分析表明,采用双合金法,使组织中细小的颗粒状富稀土相增多,形成了更多的对矫顽力有贡献的富稀土相,并且富稀土相分布于晶界上.     

Magnetic Phase Transition and Magnetic Entropy Change in La0.8Pr0.2Fe11.4Si1.6 Compound

The magnetic properties and the phase transformation of the partial substitution of Pr for La in LaFe11.4Si1.6 have been investigated by the means of X-ray diffraction (XRD) and vibrating sample magnetic (VSM). The results indicated that the single phase NaZn13-type cubic structure is stabilized for the compound La0.8Pr0.2Fe11.4Si1.6 and large values of the isothermal magnetic entropy change △SM around the curie temperature Tc~194 K in relative low magnetic fields. The maximum value |△SM|max~37.07J/kg·K-1 under a field of 1.5 T. Such large MCEs are attributed to the sharp change of the magnetization at the Curie temperature, the field-induced IEM transition and a strong temperature dependence of the critical field BC.     

Influence of Fe Content on Microstructure and Magnetic Properties of Melt-Spun SmCo-Based Alloy Ribbons

The microstructure and magnetic properties of melt-spun Sm(Co_0.88-xFe_xCu_0.10Zr_0.02)_7.5 (x = 0.1 and 0.2) alloy ribbons have been studied. The results showed that the as-spun ribbons were in a single phase, SmCo₇, with the Cu₇Tb structure. When aged in the temperature range from 720 to 900 °C, the SmCo₇ phase transformed into Sm₂Co₁₇, SmCo₅, and CoFe(Zr) phases with a minor Sm₂Co₃ phase. For the x = 0.1 alloy, a large coercivity, H_c = 8.7 kOe, was observed although the soft magnetic CoFe(Zr) phase was present in the alloy. The volume fraction of the CoFe(Zr) phase increased when the ageing temperature increased from 720 to 760 °C. At higher ageing temperature, the CoFe(Zr) phase was partially re-dissolved. With an increase in the Fe content in the alloy, the CoFe(Zr) phase increased significantly, causing the coercivity to decrease.     

Pr2Fe17-xAlx系列化合物的结构与磁熵变

采用熔炼法制备了Pr2Fe17-xAlx系列化合物。利用X射线衍射和MPMSXL-7型磁强计对样品相结构和磁熵变进行了研究。结果表明：Pr2Fe17-xAlx系化合物保持了Th2Zn17型菱方结构，其居里温度可通过成分微调达到室温附近；Pr2Fe17-xAlx系化合物在居里点附近发生的相变属于二级相变，并在较宽温区范围内保持了较大的磁熵变。该化合物在2．0T外场下的最大磁熵变达到纯金属Gd的60％左右，且其化学性质稳定，制冷温区宽，价格低，是一类具有较大应用潜力的新型室温磁制冷工质材料。     

Microstructure and Magnetic Properties of Rapidly Quenched Pr9Fe91–xBx (x=4–12) Nanocomposite Magnets

The microstructure and magnetic properties of rapidly quenched nanocomposites Pr₉Fe_91-xB_x (x=4, 5, 6, 7, 8, 8.5, 9, 10.5 and 12) have been studied in this work. The results showed that the phases present in the Pr₉Fe_91–xB_x nanocomposites were strongly dependent on the B content. The samples consist of Pr₂Fe₁₄B and α-Fe phases when the B content was low (4–8 at%), and Pr₂Fe₁₄B, α-Fe and Fe₃B when the B content was sufficiently high (>11 at%). The metastable Pr₂Fe₂₃B₃ phase appears in the intermediate B content (8–10.5 at%) and is associated with poor magnetic performance. It was further found that this metastable phase can be transformed into Pr₂Fe₁₄B, α-Fe and Fe₃B by annealing the sample at temperatures above 750 °C, leading to a more square demagnetization curve. However, the B_r of such nanocomposites decreases slightly due to the excessive grain growth during high-temperature annealing. A comparison of microstructure and magnetic properties between Pr₂Fe₁₄B/α-Fe and Pr₂Fe₁₄B/Fe₃B was also made in this work. It was found that the Pr₂Fe₁₄B/α-Fe exhibited a finer and more uniform microstructure with an average grain size of ∼10 nm, whereas a relatively coarse microstructure (grain size up to 100 nm) was observed in the Pr₂Fe₁₄B/Fe₃B. It was also found that the Pr₂Fe₁₄B/α-Fe yielded higher B_r, (BH)_max and a more square demagnetization loop, although the H_ci was slightly lower. The superior magnetic properties observed in the Pr₂Fe₁₄B/α-Fe can be attributed to the more favorable intrinsic magnetic properties of α-Fe (higher M_s and lower K) and the much finer microstructure which produces stronger inter-grain exchange coupling between the Pr₂Fe₁₄B and α-Fe phases. The results indicate that RE₂Fe₁₄B/α-Fe nanocomposites are more desirable than RE₂Fe₁₄B/Fe₃B for future development of RE-Fe-B nanocomposite magnets.     

Microstructure Evolution and Phase Formation of Fe25Ni25CoxMoy Multi-principal-Component Alloys

Metallurgical and Materials Transactions A - Fe25Ni25CoxMoy multi-principal-component alloys (MPCAs) are designed in this study; the ratio of Co and Mo is changed to study the effect on the...     

Preparation and Magnetic Properties of Melt-Spinning Nd2Fe14B/α-Fe Nanocomposite Magnets

Nd11Fe71Co8V1.5Cr1B7.5 magnet was prepared by melt-spinning and subsequently annealed. The effects of the wheel speed on the magnetic properties and microstructure were studied. The results reveal that fine nanocomposite microstructure consisting of Nd2Fe14B and α-Fe phases can be developed at an optimum wheel speed of about 21 m·s-1. After optimal annealing (640 ℃×4 min), magnetic properties of Br=0.64 T, jHc=903.5 kA·m-1 and (BH)max=71 kJ·m-3 were obtained for the bonded magnets. The addition of Cr element significantly reduces grain size, increasing the intrinsic coercivity and maximum magnetic energy product.     

Computer Simulated Magnetic Properties of Nd2Fe14B/α-Fe Nanocomposite Magnets

Micromagnetic models of assemblies of randomly oriented, exchanged coupled nanocrystals consisting of magnetically hard Nd₂Fe₁₄B and very soft alpha Fe have been simulated. The modeling of two-dimensional chessboard consisted of 50 vol. % hard and 50 vol.% soft nanocrystals with the size varying from 5, 10, 25, to 50 nm. Hysteresis curves of each model system were obtained by solving the Landau-Lifshitz-Gilbert equation by time integration of the stiff differential equations. The simulation was focused on the effect of domain size and distribution in each nano crystal of fixed size. Eventually the simulated results were compared with magnetic properties obtained from experimental results of NdFeNbB based magnetic alloys showing the identical grain sizes to the simulated model. The present study exhibited the important role of soft phase in terms of volume fraction and arrangement of the phase.     

Nb对C-Si-Mn-Cr双相钢相变规律、组织和性能的影响

  根据C Si Mn Cr和C Si Mn Cr Nb实验钢的相变规律,在实验室进行了控轧控冷实验研究,分析了微合金元素Nb对高强度热轧双相钢相变规律、组织和性能的影响。实验结果表明,Nb可显著推迟铁素体和珠光体转变,并显著降低铁素体开始转变温度,但对铁素体终止转变温度和贝氏体转变温度区间基本没有影响。经Nb微合金化后,实验钢的屈服强度和抗拉强度增幅均在100 MPa以上,屈服强度的增幅高于抗拉强度,且在强度大幅度升高的同时,伸长率下降并不明显,表明Nb的细晶强化作用对提高中温卷取热轧双相钢强度级别的效果明显。     

纳米晶Fe_3B/Nd_2Fe_(14)B粘结永磁体的磁性能研究

本文研究了粘结剂含量和温度－时间变化对纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁材料的磁性能影响。结果表明降低粘结剂含量可显著地提高纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁的磁性能；环境温度对纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁的磁性能具有重要影响，在较高的温度下其磁性能将显著下降，因此纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁只能在较低的温度环境下使用     

Microstructure and Magnetic Properties of Ni2(Mn,Fe)Ga Heusler Alloys Rapidly Solidified by Melt Spinning

The microstructure and magnetic properties of Ni₂MnGa base alloys with “Fe” substitution in place of “Mn” are studied. The processing technique used is melt spinning at wheel speeds of 20 m/s and 30 m/s followed by annealing at 1273 K (1000 °C) for 1 hour. Fe content is varied from 2 at. pct to 11 at. pct for alloys of Ni₅₀Mn_(25?x)Fe _x Ga₂₅ with Heusler stoichiometry. Austenite with B2 partial atomic ordering and premartensitic tweed structures were found at room temperature for all the alloys at different wheel speeds. After annealing at 1273 K (1000 °C) for 1 hour, austenite phase with L2₁ Heusler atomic ordering is stabilized in samples of all the processing conditions. Saturation magnetization, martensitic transformation temperature, and Curie temperature are measured. Martensite temperature and Curie temperature increase in proportion to iron content in the alloy. Saturation magnetization is sensitive to the phase content and compositional inhomogeneities.     

15Cr2Ni10MoCo14钢的淬火对时效组织和性能的影响

在７８０～９００℃淬火范围内，淬火态及淬火时效钢的硬度随淬火温度的提高而降低，淬火温度较高时时效的强化作用较小，显微组织中发现的时效过程中析出的渗碳体和Ｍｏ２Ｃ导致钢的强化。     

合金元素对Nd2Fe14B/α-Fe磁性能的影响

通过单一添加 ,研究了C ,Pr,Nb对Nd2 Fe1 4B/α Fe纳米复合永磁体磁性能的影响 ;用少量C取代B ,可以显著提高Nd9Fe85.5Nb1 .0B4 .5-yCy 永磁体的内禀矫顽力iHc,用Pr代替部分Nd可以提高双相快淬薄带的矫顽力并改善退磁曲线的矩形度。当Nb含量控制为 0 .5 %时 ,Nd2 Fe1 4B/α Fe的各项磁性能均有显著提高。采用五因子二水平正交分析方法 ,研究了Ga ,Nb ,Zr,Hf和Pr复合添加对磁性能的作用。Nb是影响剩余磁极化强度Jr 和最大磁能积 (BH) max最为显著的因子 ,而Pr对iHc 的影响最强烈。另外 ,在Nb ,Pr之间 ,Nb ,Hf之间 ,Ga与Pr以及Ga与Hf之间的交互作用也对磁性能有显著影响 ,优化的合金成分为Nd2 .2 5Pr6 .75Fe84 .5Ga1 .5Nb0 .5B4 .5,在 15m·s- 1 带速下获得的最佳磁性能为Jr=1.0 5 3T ,iHc=5 3 0 .9kA·m- 1 ,(BH) max=12 4kJ·m- 3。