( Tb,Dy) Fe2合金表面离子注入渗氮改性及抗腐蚀性能研究

采用离子注入技术在(Tb,Dy)Fe2稀土超磁致伸缩材料表面引入氮离子进行改性处理,研究了加速电压对材料表面相结构、微观形貌、表面硬度、抗酸碱腐蚀性能及磁致伸缩性能的影响.结果表明:离子注入渗氮后,(Tb,Dy)Fe2合金表面的REFb相分解,生成了REN,α-Fe和Fe8N新相,材料表面微观形貌发生了明显变化,表面硬度明显提高.通过测试极化曲线研究了渗氮前后(Tb,Dy)Fe2合金在不同PH值NaCl溶液中的抗酸碱腐蚀性能,发现pH值相同条件下渗氮处理后(Tb,Dy) Fe2合金的自腐蚀电位Ecorr较渗氮前明显正移且有钝化现象发生.在加速电压140 kV,离子注入剂量5.0×1017 ion.cm -2条件下渗氮处理的(Tb,Dy)F合金,处于20℃,3.5％ NaCl溶液环境中,pH=4时,△Ecorr=0.23413 V; pH =7时,△Ecorr =0.18992 V; pH=10时,△Ecorr =0.01268 V,渗氮处理后(Tb,Dy)Fe2合金的抗酸腐蚀性能明显增强,抗碱腐蚀性能变化不明显.随着pH值的增大,渗氮与未渗氮(Tb,Dy) Fe2合金的抗腐蚀性能均变差.由于离子注入表面渗氮的渗氮层很薄,渗氮温度很低,渗氮处理没有破坏材料的内部基体结构,因此渗氮后材料渗氮处理没有破坏材料的内部基体结构,其磁致伸缩性能几乎未受影响.研究表明离子注入渗氮是(Tb,Dy)Fe2磁致伸缩材料表面改性的一种有效方法.     

Influence of gadolinium on microstructure and magnetic properties of sintered NdGdFeB magnets

The effect of Gd content on microstructure and magnetic properties of sintered Nd33.03-xGdxFe65.65B1.32 (x=0-2) was studied in this paper to improve the thermal stability of NdFeB and to reduce the raw material cost. The results showed that better magnet performance could be obtained by adding Gd (0-1.5 wt.%) with partial substitution of Nd in Nd33.03-xGdxFe65.65B1.32. It was also found that the Nd33.03-xGdxFe65.65B1.32 magnets showed the best performance when Gd addition increased to 1.0 wt.%. The temperature coefficient Br (α) could be improved from -0.15%/oC to -0.063%/oC (maximum work temperature 120 oC) and the Curie temperature could be improved from 315 oC to 323 oC because the Gd2Fe14B had positive temperature coefficient Br (α) and higher Curie temperature than that of Nd2Fe14B. The coercivity could be improved from 10.2 to 11.48 kOe and the microstructure was close to ideal microstructure. The magnetic performance decreased sharply by adding Gd (above 2 wt.%) with partial substitution of Nd in Nd33.03-xGdxFe65.65B1.32 because the Gd element concen-trated in the grain boundaries.     

Fe-Ga磁致伸缩材料研究进展

Fe-Ga合金是人们在新型高性能磁致伸缩材料探索中的一个重要发现,具有高应力灵敏度、良好的热-机械性能和磁致伸缩性能,填补了传统磁致伸缩材料和稀土超磁致伸缩材料之间的空白,在超声领域和微位移器等方面有较大的潜在应用价值,应用前景广阔。本文从Ga含量及相结构、第三组元、制备方法、压力和温度四个部分阐述Fe-Ga磁致伸缩材料的研究进展及研发趋势,总结了Ga含量及相结构、第三组元对Fe-Ga合金的磁致伸缩性能的影响,Fe-Ga合金的磁致伸缩性能与Ga含量密切相关,不同的第三组元对合金磁致伸缩性能的影响也不同;Fe-Ga合金的制备方法主要有定向凝固法、甩带急冷法、轧制法、拉丝法等方法,比较了各种制备方法对材料性能的影响;阐述了应力场和温度对Fe-Ga合金的磁致伸缩性能的影响,其中应力场对Fe-Ga合金的磁致伸缩性能有积极影响,但Fe-Ga合金磁致伸缩的温度依赖性比较复杂,磁致伸缩随温度变化的幅度与趋势都取决于合金结构。     

Structure and permanent magnetic properties of SmFex （x=3-8） melt spun ribbons during heat treatment

Compounds with the composition SmFex（x=3–8） were prepared by melt spun method at a velocity of 40 m/s and subsequent annealing at temperature between 600–1000 ℃. The crystal structures of the as-quenched and as annealed powders were investigated by XRD methods with following Rietveld analysis. The glass forming ability could be enhanced by the increase of Sm content to x≤5.Metastable Sm5Fe17-type structure existed when 3≤x≤5 and temperature was lower than 800 ℃. SmFe2-type structure could be stable up to 1000 ℃ when x〉3 and temperature was under 800 ℃. The content of SmFe2-type decreased with the increase of x value and increased with temperature lower than 800 ℃, from which SmFe2-type started to bring the transition to SmFe3-type. As for Sm5Fe17-type compounds with x=3.4, the highest coercivity of 33.6 kOe could be obtained under a velocity of 30 m/s and heat treated under 700 ℃×1h.     

高性能烧结NdFeB生产关键技术研究

采用薄形结晶器铸锭技术，气流磨窄粒度控制技术，低氧含量控制技术，高取向磁场成型技术等成功地批量生产了磁能积为365kJ/m∧3和磁能积为310kJ/m∧3，矫顽力为1640kA/m的NdFeB磁体。研究表明：获得尺寸细小的片状晶铸锭、平均粒度小于4.0μm的窄粒度分布的粉末，高取向度且晶粒细小组织均匀的烧结体是生产高性能NdFeB的关键。     

Fe含量对快淬SmFe合金结构的影响

在轮速为40 m·s-1快淬制备不同Fe含量的亚稳态快淬SmFe x(x=7.5,8.0,8.5,9.0,9.5,10.0,10.5,11.0,12.0,13.0)合金,经过800℃退火处理60 min,采用XRD分析了快淬SmFe x合金退火前后的相组成和晶体结构,并结合Rietveld结构精修方法分析了TbCu7型SmFe9相的晶体结构。结果表明:快淬SmFe x合金在化学计量数SmFe x(x=7.5~8.0)时,形成Th2Zn17型Sm2Fe17和少量的SmFe2;随着Fe含量增加,在x=8.5~13.0时,由平衡相转变成亚稳TbCu7型SmFe9相,α-Fe含量逐渐增多。随着Fe含量增加,SmFe合金的晶格常数a不断减小,而晶格常数c,c/a不断增大。在TbCu7型SmFe9相中Fe原子分别位于2e,3g,6l晶位,Sm原子自由占据1a晶位。2e晶位哑铃状Fe-Fe原子对的的占位趋于无序。退火后SmFe x合金在化学计量数x=8.5,9.0时,由亚稳相TbCu7型SmFe9转变为平衡Th2Zn17型Sm2Fe17相;在化学计量数SmFe x(x=9.5~13.0)时,保持TbCu7型SmFe9不变。退火使2e晶位哑铃状Fe-Fe原子对有序排列,Sm原子在1a晶位的占位率提高,晶体结构由TbCu7型结构转变成Th2Zn17型结构,但Fe含量超过一定值后,无法继续这种转变。退火SmFe x合金晶体结构的晶胞参数变化规律与淬火态相同,退火SmFe合金中α-Fe含量增多。     

Phase and microstructure of TbCuT-type SmFe melt-spun powders

The SmxZr0.3Fe9.1-xCo0.6(x=0.8,0.9,1.0) powders were prepared by melt-spun method with different quenching velocities.The phase and microstructure were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The Th2Zn17-type structure of the as-cast state changed to TbCu7-type after quenching to a rotating molybdenum roll under certain velocity,and the formation of TbCu7-type phase was strictly depending on the Sm content and roll speed.The SEM morphology showed that the Fe-rich zone was typically fish-bone structure and TEM diffraction pattern indicated the nano-scale crystal size with TbCu7-structure when x=0.9,and FCC type γ-Fe on the basis of α-Fe formed in the non-equilibrium solidification could be detected by selected area electron diffraction(SAED) indexing in the x=0.8 samples.     

Fe-Ga合金磁致伸缩材料的研究进展

与稀土磁致伸缩材料Tefernol-D相比, Fe-Ga合金具有饱和磁场低、磁导率高、强度高、脆性小和温度特性好等特点, 其潜在的应用范围更为广泛, 尤其适用于强震动、大负荷、强腐蚀等较为恶劣的工作环境. 重点介绍了Fe-Ga磁致伸缩材料的制备工艺、合金成分、微观结构及性能等方面的研究进展.     

快冷厚带-氢破碎-磁场成型工艺制备高性能烧结钕铁硼磁体

对比分析了我国与西方国家生产烧结钕铁硼磁体工艺差距，指出了快冷厚带制备工艺是生产烧结钕铁硼磁体关键性工艺、核心技术。分别采用快冷厚带-氢破碎-磁场成型工艺和普通铸锭-氢破碎城场成型工艺制备同一成分的烧结钕铁硼磁体。结果表明：钕铁硼快冷厚带“柱状晶”穿透整个带厚、无等轴晶区、无α—Fe相、三相(主相Nd2Fel4B、富Nd相和富B相)分布均匀、耐腐蚀性能好；氢破碎后沿富Nd相均匀破碎，主相晶粒完整；气流磨后为2．8～3．2μm单晶粉末；快冷厚带可以明显提高磁体的各项性能。     

HDDR各向异性NdFeB研究进展

HDDR工艺目前已经成为了制备各向异性NdFeB磁粉的最主要方法.总结了本世纪以来HDDR法制备各向异性磁粉的各向异性成因、HDDR处理工艺、添加元素等方面取得的进展,以及磁粉粒度、粘结剂选择、成型方法对磁体性能的影响.