NdDyFeBSn永磁合金显微组织的高分辨分析

用透射电镜研究了烧结NdDyFeB和NdDyFeBSn合金的显微组织 .添加Sn的合金 ,晶界富Nd相与基体 2∶1 4∶1相润湿性良好 .合金的主要相仍然是硬磁相Φ(2∶1 4∶1相 )、富硼相 η(Nd1 εFe4B4)和fcc结构的富Nd相 .高分辨分析表明 ,NdDyFeBSn合金的晶粒内出现非共格的粒状沉淀 ,尺寸 2～ 1 0nm .选区电子衍射分析表明 ,该缺陷相结构同于α Fe .X射线衍射分析也肯定 ,在含Sn合金中有α Fe析出 .而在NdDyFeB合金中观察不到α Fe衍射 ,合金晶粒内也几乎无缺陷     

HDDR工艺对Nd_2Fe_(14)B基磁粉磁性能的影响

氢化 歧化 脱氢 再复合(简称HDDR)工艺是生产Nd2Fe14B基永磁粉的一种特殊方法·研究了HDDR工艺制造高性能Nd Fe B磁粉时,不同HD温度和不同DR温度对磁粉性能的影响规律·利用XRD方法分析了不同工艺条件下样品的相组成·结果发现,Nd Fe B磁粉的磁性能对HD温度和DR温度敏感,合金元素Ga,Al的添加可改善磁粉的磁性能·有害相α Fe的消除可提高磁粉的剩磁,但均匀化处理不能将α Fe完全消除·HD过程中,主相Nd2Fe14B分解为NdH2,α Fe和Fe2B三相,DR过程后,主相晶粒得到细化·计算表明,主相晶粒尺寸大约为0 28μm·     

烧结NdFeB系永磁材料的TEM观察

利用透射电镜对经过机械性能测试的烧结 Nd Fe B系永磁材料进行了微观组织结构的观察和分析 .结果表明 ,合金元素对 Nd Fe B的组织影响不大 ,主要都包括基体相 Nd2 Fe14B和富 Nd相 ,还有少量富 B相 ,含 Nd的样品中出现了棒状沉淀相粒子 .但是 ,在各种样品中都发现基体相中存在位错 ,这是和其他研究者的结果完全不同的 .     

NdFeCoBZrGa合金各向异性磁粉的制备

HDDR(氢化-歧化-脱氢-再结合)工艺是一种用于生产各向异性Nd2Fe14B基磁粉的有效方法.主要研究了真空HDDR工艺(即合金在真空中以较快速率加热到820℃左右,然后在一定的氢气压力下吸氢歧化)及添加合金元素Ga对Nd13Fe64.4-yCo16B6.5Zr0.1Gay(y=0.1,0.3,0.5,1.0)合金磁性能的影响规律.结果表明,真空HDDR工艺的吸氢歧化阶段是促使材料产生磁各向异性的关键,脱氢阶段采用低真空高温制度是材料获得高各向异性的保证;合金元素Ga有助于细化主相晶粒,提高材料的综合磁性能,其最佳原子分数添加量为0.5%;成分为Nd13Fe63.9Co16B6.5Zr0.1...     

Zr和Nb掺杂对Nd2Fe14B/α-Fe纳米复合永磁薄带显微组织和磁性能的影响

比较了Zr,Nb掺杂对Nd8.60Fe80.80Cu0.3Zr2-xNbxB8.30(x=0,1,2)交换耦合纳米复合永磁薄带相组成、显微结构和磁性能的影响. 结果表明:Zr和Nb均能有效地抑制晶粒的长大. Zr与B结合生成ZrB2,消耗了合金中部分B元素,导致合金中硬磁性相N2Fe14B含量的减少. 与Zr相比,Nb能更有效地抑制晶粒长大,提高样品磁滞回线的方形度. 仅掺杂Nb的晶化样品Nd8.60Fe8 0.80Cu0.3Nb2B8.30具有最佳的磁性能:Br=0.89T,H ci=479.1kA·m-1,(BH)max=107.4kJ·m-3.     

Nb对快淬Nd10Fe84B6合金微观组织和磁性能的影响

研究了添加Nb对快淬Nd10Fe84B6合金磁性能、微观组织和晶化温度的影响.结果表明:添加Nb可以提高快淬态合金中非晶相的热稳定性,减小最佳退火温度和晶化起始温度之间的温度差,抑制热处理时α-Fe和Nd2Fe14B晶粒的预先析出和长大,有效细化了晶粒,提高磁性能.快淬Nd10Fe83Nb1B6合金经过715℃热处理10 min,磁性能达到Br=0.90 T,iHc=750 kA/m,(BH)max=120 kJ/m3,较之Nd10Fe84B6合金,内禀矫顽力提高了25%,最大磁能积提高了14%.     

廉价R-Fe-B系烧结永磁材料的制备

为了综合利用我国稀土资源,降低Nd—Fe—B永磁合金的成本,研究了廉价(Nd、Pr)—Fe—B和(Ce、Nd、Pr)—Fe—B永磁材料的化学成分,制造工艺与磁性能的关系及其变化规律。添加Al可以大幅度提高合金的矫顽力。(Nd、Pr)—Fe—B合金最佳磁性能:Br=1.25T,M_Hc=714.3kA/m,(BH)_(max)=297.5kJ/m~3。(Nd、Pr)_(1-y)Ce_y—Fe—B合金的磁性能随Ce含量增加而降低。研究测定了合金的居里温度609～590K,剩磁可逆温度系数-0.094～-0.119％/K。观察分析了合金的显微组织,并测定了合金的密度,硬度及电阻率。     

热处理气氛对Nd10Fe79Zr1Co4B6合金相组成和磁性能的影响

研究了热处理气氛对快淬Nd10Fe79Zr1Co4B6合金相组成和磁性能的影响.结果表明:Nd10Fe79Zr1Co4B6快淬合金薄带在热处理时通入氮气会发生吸氮反应,相结构由纯氩气热处理时的Nd2Fe14B和α-Fe两相组织转变为Nd2Fe14B、NdBN2和α-Fe三相组织,且随着氮气分压的提高,热处理后样品中α-Fe相和NdBN2相的体积分数逐渐增多.Nd10Fe79Zr1Co4B6样品的剩磁Br、内禀矫顽力iHc和最大磁能积(BH)m ax随着热处理时氮气分压的提高而下降.     

Nd（10-x）Fe81.2B8Cu0.8Wx合金的结构及磁性研究

利用机械合金化法制备了Nd(10-x)Fe81.2B8Cu0.8Wx系列合金.采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和振动样品磁强计(VSM)对不同球磨时间制备的样品的显微结构及其磁性能进行了研究.结果表明,适量的添加W能够促进硬磁相Nd2Fe14B的析出,并且提高磁体的抗氧化性.W的质量分数为1%时样品综合磁性能最佳.     

Nd-Fe-B包晶合金的定向凝固组织及相选择

对Nd11.76Fe82.36B5.88包晶成分和Nd13.5Fe79.75B6.75过包晶成分合金进行了高梯度定向凝固和激光快速定向凝固实验,研究了Nd-Fe-B合金组织形成及相选择与凝固参量(温度梯度G,生长速度V,合金成分C0)之间的对应关系.针对包晶相为无固溶度的化学计量比结构的Nd-Fe-B合金体系,讨论计算了合金定向凝固过程γ-Fe及包晶T1相的界面温度随生长速率的变化,获得了Nd-Fe-B合金定向凝固相/组织选择图,确定了合金凝固中各相及生长形态转化的条件.Bridgman定向凝固实验中,随着抽拉速率的增加,T1相由平面/小平面向枝晶形貌转变;Nd13.5Fe79.75B6.75合金的激光实验中,凝固速率由4.4~5.0mm/s时,领先析出的组织由γ-Fe枝晶转变为T1相枝晶.实验结果与理论计算给出的相/组织选择图吻合较好.     

Nd－Fe－B合金的组织与组成对其腐蚀行为的影响

研究了Ｎｄ－Ｆｅ－Ｂ合金的组织与组成对其腐蚀行为的影响。对Ｎｄ－Ｆｅ－Ｂ合金各主要组成相在纯水和ＮａＣｌ溶液中电位进行了测定，结果表明Ｅ（富Ｎｄ相）＜Ｅ（基体相）＜Ｅ（富Ｂ相）。Ｎｄ－Ｆｅ－Ｂ合金的腐蚀特征是晶界处的富钕相优先腐蚀，然后向晶粒内Ｎｄ２Ｆｅ（１４）Ｂ基体相扩展。环境腐蚀试验结果表明，Ｎｄ－Ｆｅ－Ｂ合金中加入Ｄｙ后，耐蚀性提高；加入Ａｌ后，则耐蚀性有所下降。     

速凝铸造工艺制造高性能烧结Nd-Fe-B磁体

研究了用速凝铸造工艺制造高性能烧结Nd Fe B磁体·同传统的铸锭工艺相比,速凝铸造工艺细化柱状晶,阻止α Fe枝晶相的产生,改善了铸态合金的微观结构·柱状晶宽度基本在5～25μm之间,尺寸较均匀;在制粉过程中容易得到粒度分布较好的磁粉;富Nd相分布较好,所以在较低烧结温度下可得到较高密度的磁体;由于具有细小均匀的微结构,利用速凝铸带工艺烧结出的磁体具有更高的Br,Hci和(BH)max·     

新型Mg-Li-Al-Mn-Si-Ca合金的显微组织和力学性能

向Mg-Li合金中添加微量元素Al,Mn,Ca和Si,研究了合金的显微组织与力学性能.室温下合金具有良好的加工性能,能够轧制成薄板.通过金相观察可知,添加元素能够细化组织中的α相,并生成颗粒状及细条状物质,通过SEM和EDX分析可知,其为不同添加元素之间形成的化合物.室温下拉伸测试结果表明,合金具有较高的强度和延伸率,随着不同元素的逐步添加,合金强度不断提高,最终σ0.2可以提高17.06%,σb可以提高13.16%,而延伸率有所降低,但仍具有较高值,这是添加元素强化的结果.     

Magnetic properties and thermal stability of sintered Nd-Fe-B magnet with Dy-Ni additive

A sintered(Nd_(0.8)Pr_(0.2))_(30.7)FebalB_(0.98)Cu_(0.2) magnet with 3% intergranular Dy_(85)Ni_(15) additive is prepared to study the magnetic properties and thermal stability of the Nd-Fe-B magnet. The results show that the magnet with or without additive obtains its optimum comprehensive magnetic properties at the sintering temperature of 1 030 ℃ and 1 040 ℃, respectively. The maximum coercivity of the magnet with additive reaches 15.16 k Oe, while that of the magnet without additive is just 11.88 k Oe. Further investigation on microstructure indicates that the grains of the magnet with additive form a modified "core shell" structure. Adding Dy_(85)Ni_(15) can significantly enhance the coercivity of Nd-Fe-B magnet and thus decrease its coercivity temperature coefficient.     

Martensitic transformation and magnetic properties of aged Ni-Fe-Ga-Ti shape memory alloy

This article reports the effect of ageing on the microstructure, martensitic transformation, magnetic properties, and mechanical properties of Ni₅₁Fe₁₈Ga₂₇Ti₄ shape memory alloy. There are five specimens of this alloy aged at 573 up to 973 K for 3 h per each. This range of ageing temperature greatly affects the microstructure of the alloy. As the ageing temperature increased from 573 up to 973 K, the microstructure of Ni₅₁Fe₁₈Ga₂₇Ti₄ alloy gradually changed from the entirely martensitic matrix at 573 K to the fully austenitic microstructure at 973 K. The volume fraction of precipitated Ni₃Ti particles increased with the ageing temperature increasing from 573 to 773 K. Further increasing the ageing temperature to 973 K decreased the content of Ni₃Ti in the microstructure. The martensitic transformation temperature was decreased steadily by increasing the ageing temperature. The magnetization saturation, remnant magnetization, and coercivity increased with the ageing temperature increasing up to 773 K. A further increase in ageing temperature decreased these magnetic properties. Moreover, the hardness values were gradually increased at first by increasing the ageing temperature to 773 K, and then dramatically decreased to the lowest value at 973 K.     

Effect of minor Sc on the microstructure and mechanical properties of AZ91 Magnesium Alloy

The as-cast and heat-treated microstructures and mechanical properties of the AZ91 magnesium alloys with and without minor Sc addition were investigated and compared in this paper. The results indicated that adding0.15–0.45 wt% Sc to the as-cast AZ91 alloy not only could modify and refine the Mg_(17)Al_(12) phase but also suppress the formation of the Mg_(17)Al_(12) phase. At the same time, the grains of the Sc-containing as-cast AZ91 alloys were also effectively refined. As a result, the mechanical properties at room temperature(RT) for the Sccontaining as-cast AZ91 alloys were effectively improved. In addition, adding 0.15–0.45 wt%Sc to the AZ91 alloy promoted the formation of the continuous precipitates(CP) during the aging treatment in spite of that the formation of the discontinuous precipitates(DP) was simultaneously suppressed. Accordingly, the Sc-containing as-aged AZ91 alloys obtained the relatively higher mechanical properties at RT than the as-aged AZ91 alloy.     

高磁能积低温度系数的铁基永磁合金的磁性能与组织结构

本文研究了Co和Al的添加对NdFeCoAlB永磁合金磁性能与组织结构的影响。获得一种磁能积为278.6～318.4kJ/m~3(35～40MGOe),磁感可逆温度系数α293～373K=-0.06～-0.08％/K的NdFeCoAlB系5元合金。Co主要进入四方相,提高合金的居里点,降低磁感可逆温度系数。当含Co量较高时,在合金中形成了具有MgCu_2型结构的Nd(FeCo)_2相,使合金永磁性能恶化。Al主要进入四方相,使四方相晶粒和富B相块度细化,提高了合金的矫顽力。进一步提高Al含量时,在合金中形成了新相,使合金永磁性能恶化。     

Effect of cooling rate on the magnetic properties of Fe53Nd37Al10 alloy

The effect of cooling rate on the magnetic properties of the Fe₅₃Nd₃₇Al₁₀ alloy prepared by different methods, i.e., suction casting and melt spinning at different rates, was investigated. The Fe₅₃Nd₃₇Al₁₀ ribbon at the wheel speed of 5 m·s^?1 exhibits the highest coercivity in the samples. Two hard magnetic phases are detected from the hysteresis loops of the 5 m·s^?1 ribbon at all temperatures below room temperature. Their appearance is associated with different exchange coupling interactions, which are between the two kinds of hard magnetic phases or between the hard magnetic phase and the soft magnetic phase.     

Morphology and quantitative analysis of O phase during heat treatment of hot-deformed Ti<Subscript>2</Subscript>AlNb-based alloy

A 1040℃-hot-deformed Ti₂AlNb-based alloy solution-treated at 950℃ and aged at different temperatures was quantitatively investigated. The microstructure, size of the phase, and microhardness of the deformed alloys were measured. The results indicated that the microstructure of the deformed Ti₂AlNb-based alloy specimens comprise coarse O lath, fine O lath, equiaxed O/α₂, and acicular O phase. More O phase was generated in the deformed alloy after heat treatment because the acicular O phase was more likely to nucleate and grow along the deformation-induced crystal defects such as dislocations and subgrain boundaries. After deformation and subsequent heat treatment, the acicular O phase of the resultant alloy became finer compared to that of the undeformed alloy, and the acicular O phase became coarser and longer with the elevated aging temperature, while the width of the O lath exhibited unobvious variations. The hot deformation facilitated the dissolution of the O lath but accelerated the precipitation of the acicular O phase. When the 950℃-solution-treated deformed Ti₂AlNb-based alloy was then aged at 750℃ for different periods, the phase content was nearly invariable, O and B2 phases eventually reached equilibrium, and the microstructure became stable and homogeneous.