B_2型Fe_3Al金属间化合物的高温氧化行为

研究了Fe3Al、Fe3Al(Cr))两种合金在600℃、750℃、950℃的静态氧化行为及其750℃的周期氧化行为,分析了相应的氧化膜结构和形貌,探讨了氧化膜的成长机理。结果表明,由于高温下Fe3Al基金属间化合物表面形成一层致密的A12O3氧化膜而具有优良的抗氧化性能。在950℃高温时,具有比1Cr13不锈钢好得多的抗氧化性能。2at%Cr的加入有利于稳定的α-Al2O3的形成。750℃以下,Fe3Al(Cr)合金的氧化增重低于Fe3Al,前者的氧化膜为纯α-Al2O3,而后者的还含有少量的γ-Al2     

(Ni,Pd)Al涂层的高温氧化

在M38镍基高温合金上电镀Pd—20mass％Ni合金，采用低压固体粉末包埋渗铝方法制备钯改性铝化物涂层。XRD分析表明，涂层主要由β—(Ni，Pd)Al相组成。利用TGA、SEM等方法，研究了涂层在800℃～l100℃的初期高温氧化行为。结果表明，800℃、900℃和l100℃下，氧化动力学遵循抛物线规律，1000℃则不是；在800℃和900℃中等温度下，(Ni，Pd)Al涂层表面氧化产物除θ—Al2O3和α—Al2O3外，还含有少量的γ—Al2O3；在1000℃下，涂层表面存在θ—Al2O3和α—Al2O3两种氧化物；在l100℃下，涂层表面氧化产物主要是α--Al2O3。另外，在各温度下涂层表面的氧化产物中都含有少量的TiO2，并且随着温度升高，含量增加.     

金属型铸造Fe3Al合金的高温抗氧化行为

采用静态增重法测定了中频感应炉熔炼、金属型冷却制备的Fe3Al合金在700、850、1000℃的高温氧化行为,700、850℃时合金的氧化动力学曲线基本符合抛物线规律,1000℃的则不符合;合金在氧化过程中表现为完全抗氧化级.X射线衍射、扫描电镜和能谱分析表明,700℃×125h的氧化膜主要由FeAl2O4、Cr2O3和少量的Al2O3组成;850、1000℃时氧化膜分为两层,内层主要由FeAl2O4和Fe2O3组成,表层为Al2O3,在实验时间内Al2O3氧化膜没有完全覆盖内层氧化膜;随着氧化温度的升高,氧化时间的延长,合金表层的Al2O3氧化膜将由θ-Al2O3向α-Al2O3转变.     

纳米NixZn1-xFe2O4颗粒的制备及其磁性能

采用水热法制备了不同镍锌比的纳米NixZn1-xFe2O4粉体.采用X射线衍射、透射电镜(TEM)、振动样品磁强计(VSM)等方法对制备的样品进行了表征,物相分析结果表明,在200℃水热5 h可以得到纯的纳米NiFe2O4粉体,在200℃水热5 h制备的Ni0.5Zn0.5Fe2O4中含有γ-Fe2O3,在220℃水热5 h可以得到纯Ni0.5Zn0.5Fe2O4纳米粉体.水热温度为220℃时制备的ZnFe2O4中仍然存在γ-Fe2O3.TEM结果表明,NixZn1-xFe2O4粒子为球形,粒径为10～20nm.磁滞回线结果表明纳米NixZn1-xFe2O4具有较好的磁性能,其中Ni0.5Zn0.5Fe2O4纳米粒子具有最大的饱和磁化强度(Ms),ZnFe2O4具有最大的矫顽力(Hc)值.     

溶胶-凝胶法制备的Al2O3涂层及其对γ-TiAl合金的高温氧化防护

以异丙醇铝(Al(OC3H7)3)为原料,采用溶胶-凝胶法在γ-TiAl基合金表面制备Al2O3涂层.以空白样品做对照,研究涂层的作用机制以及涂层对γ-TiAl基合金1 000 ℃高温氧化行为的影响.结果表明:采用浸涂工艺制备的涂层表面均匀、无裂纹,主要由γ- Al2O3相组成,厚度约为0.8 μm;等温氧化110 h后,空白试样和Al2O3涂层试样的氧化抛物线速率常数分别为4.85×10-12 和 3.31×10-13 g2/(cm4-s),涂层明显提高合金的抗氧化能力及抗循环氧化能力;空白样品上形成的氧化膜出现分层现象,而在涂层样品的Al2O3涂层中存在金红石型TiO2和α-Al2O3混合物.     

低压等离子喷涂NiCoCrAlYTa涂层的氧化动力学

采用低压等离子喷涂技术在镍基单晶高温合金上制备NiCoCrAlYTa涂层,研究涂层在900、1000和1100℃下恒温氧化200h的氧化动力学规律。通过表面XRD和SEM分析,初步探讨了氧化动力学规律与氧化产物的关系。结果表明：900℃时NiCoCrAlYTa涂层的氧化曲线符合对数规律,氧化产物主要为θ-Al2O3相;1000℃时NiCoCrAlYTa涂层的氧化曲线符合抛物线规律,氧化产物主要是θ-Al2O3和α-Al2O3相的混合物;1100℃时NiCoCrAlYTa涂层的氧化符合立方规律,氧化产物主要是α-Al2O3相。根据实验结果经计算得到NiCoCrAlYTa涂层氧化过程中θ-Al2O3的形成激活能为151．78kJ／mol,α—Al2O3的形成激活能为270．25kJ／mol。     

凝露状态下SO2对A3钢腐蚀机理的影响

采用红外光谱、电化学交流阻抗和扫描电镜等方法研究了大气中对金属腐蚀性最强的污染物SO2在凝露状态下对A3钢的腐蚀作用规律.结果表明,A3钢在加SO2试验环境中腐蚀失重随试验时间延长呈正指数变化规律;试样表面呈龟裂状腐蚀形貌,红外光谱的分析结果显示出腐蚀产物为FeSO4@7H2O、Fe2(SO4)3@9H2O和γ-FeOOH,还含有δ-FeOOH及少量的Fe(OH)2和Fe3O4.A3钢在未加SO2试验环境中腐蚀失重随时间呈直线变化规律;腐蚀产物主要为Fe2O3和γ-FeOOH;试样表面未形成连续的腐蚀产物膜.     

纳米γ-Al2O3的溶胶-凝胶法制备及表征

异丙醇铝为先驱体,异丙醇为溶剂,乙酰乙酸乙酯为螯合剂,聚乙二醇(PEG1000)为分散剂,硝酸为胶溶剂,采用溶胶-凝胶法制备了纳米γ-Al2O3.并采用DTA/TG,XRD,TEM等测试技术对纳米γ-Al2O3粉体进行表征.结果表明,通过溶剂、螯合剂、分散剂和胶溶剂的协同效应,在750℃煅烧条件下,γ-Al2O3粒子形貌为针状结构,长度为20～30 nm;在900℃煅烧条件下,γ-Al2O3粒子形貌为颗粒状,平均晶粒尺寸为10 nm左右;纳米γ-Al2O3粒子尺寸均一、分散性良好.     

单分散粒径可控γ-Fe2O3纳米颗粒的制备及表征

采用溶剂热法制备出具有尺寸可调、分散性好和强磁性的纳米γ-Fe2O3颗粒。分别采用XRD、XPS、FESEM、TEM和超导量子干涉仪(SQUID)对其结构、组分、形貌和磁性进行表征,研究氯化铁的浓度,不同的表面活性剂和反应温度对磁性纳米颗粒结构形貌和直径的影响。结果表明:制备得到的产物为反尖晶石结构、具有单分散性的γ-Fe2O3纳米颗粒,粒径在50~400 nm之间可调。反应温度对纳米颗粒的相组成和形貌影响比较显著,在140℃下得到α-Fe2O3相,在160℃下得到γ-Fe2O3相,而在180与200℃下得到Fe3O4相。纳米颗粒尺寸随着氯化铁浓度的增加而增大,随着十二烷基苯磺酸钠(SDBS)的加入而减小。在室温下,γ-Fe2O3纳米颗粒具有较强磁性,当粒径为50 nm时其矫顽力可以达到1.4 kA/m。这将在磁性复合光催化剂和生物医学领域具有潜在的应用价值。     

含铁铜基陶瓷复合材料高温氧化行为与耐磨性研究

在25,250,350和450℃高温摩擦磨损实验条件下,对两种不同铁含量的Cu基摩擦材料进行高温氧化行为及耐磨性研究。结果表明:Fe在Cu基体中的尺寸、分布影响Cu基摩擦材料的高温抗氧化性和耐磨性,随实验温度升高,Cu基摩擦材料试样中Cu氧化产物为Cu2O,Fe从Fe2O3转变为Fe3O4,金属氧化膜厚度逐渐增加;Fe以小尺寸、均匀分布于Cu基体时,更有利于提高Cu基体整体的抗氧化性能,在350~450℃可形成稳定的氧化膜降低粘着磨损,展现出了较好的高温耐磨性能;而Fe以较大尺寸分布在Cu基体中时,则使Cu基体出现氧化不均匀现象,不利于高温耐磨性能的提高。     

Zr对PrFeB非晶合金晶化的影响

采用DTA(差热分析仪）,XRD（X射线衍射）研究添加元素Zr对PrFeB非晶合金的形成,组织结构的影响,结果表明,PrFeB非晶薄带最终晶化为α－Fe和Pr2Fe14B相,晶化过程中析出亚稳相Pr2Fe23B3,非晶合金中添加1、2at%zr元素可使αFe相的起始晶化温度升高,且无亚稳相Pr2Fe23B3析出,同时细化α－Fe晶粒。     

NANOCRYSTALLINE STRUCTURE AND INITIAL PERMEABILITY OF ANNEALED Fe_（73．5）Cu_1W_3Si_（13．5）B_9 Alloy

ＮＡＮＯＣＲＹＳＴＡＬＬＩＮＥＳＴＲＵＣＴＵＲＥＡＮＤＩＮＩＴＩＡＬＰＥＲＭＥＡＢＩＬＩＴＹＯＦＡＮＮＥＡＬＥＤＦｅ_（７３．５）Ｃｕ_１Ｗ_３Ｓｉ_（１３．５）Ｂ_９ＡｌｌｏｙＺＨＡＮＧＸｉａｎｇｙｉ,ＺＨＡＮＧＪｉｎｇｗｕａｎｄＺＨＥＮＧＹａｎｇｚｅ?..     

Effects of Zr on crystallization kinetics of Pr—Fe—B amorphous alloys

The effects of Zr on crystallization kinetics of Pr-Fe-B amorphous alloys have been investigated by DTA and XRD methods.It was found that for Pr8Fe86-xZrxB6(x=0,1,2)amorphous alloys,the final crystallized mixture is α-Fe and Pr2Fe14B,and the metastable Pr2Fe23B3 phase occurs during crystallization of Pr8Fe86B6 amorphous alloy,not during crystallization of Pr8Fe86-xZrxB6(x=1,2)amorphous alloys,By analyzing the activation energy of crystallization,the formation of an α-Fe/Pr2Fe14B composite microstructure with a coarse grain size in annealed Pr8Fe86B6 alloy,is attributed to a difficult nucleation and an easy growth for both the α-Fe and Pr2Fe14B in the alloy.The addition of Zr can be used to change the crystallization behavior of the α-Fe phase in Pr-Fe-B amorphous alloy,which is helpful to reduce the grain size for the α-Fe phase.     

Interfacial Microstructure and Its Influence on Resistivity of Thin Layers Copper Cladding Steel Wires

The interfacial microstructure and resistivity of cold-drawn and annealed thin layers copper cladding steel (CCS) wires have been systematically investigated by the methods of scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and resistivity testing. The results showed that the Cu and Fe atoms near interface diffused into each other matrixes. The Fe atoms diffused into Cu matrixes and formed a solid solution. The mechanism of solid solution is of substitution type. When the quantity of Fe atoms exceeds the maximum solubility, the supersaturated solid solution would form Fe clusters and decompose into base Cu and α-Fe precipitated phases under certain conditions. A few of α-Fe precipitates was observed in the copper near Cu/Fe interfaces of cold-drawn CCS wires, with 1–5 nm in size. A number of α-Fe precipitates of 1–20 nm in size can be detected in copper near Cu/Fe interfaces of CCS wires annealed at 850°C. When annealing temperature was less than 750°C, the resistivity of CCS wires annealed was lower than that of cold-drawn CCS wires. However, when annealing temperature was above 750°C, the resistivity of CCS wires was greater than that of cold-drawn CCS wires and increased with rising the annealing temperature. The relationship between nanoscale α-Fe precipitation and resistivity of CCS wires has been well discussed.     

Precipitation of a-Fe from Fe84-xSi4B12+x (x=1,3) Amorphous Alloys Under High Magnetic Field Annealing

This work aims to investigate the effects of high magnetic field annealing (HMFA) on the precipitation of α-Fe from Fe84-xSi4B12+x (x =1,3) amorphous precursors.Isothermal annealing process for Fe81Si4B15 and Fe83Si4B13 amorphous ribbons has been performed with and without the magnetic field.The magnetic field shows the effects of increasing the nucleation rate and decreasing the grain size of α-Fe crystals simultaneously,during the crystallization processes of the investigated amorphous alloys.By applying HMF,α-Fe crystals with more homogeneous distribution and smaller grain size are achieved in the amorphous matrix,which is crucial helpful to improve the magnetic properties for Fe-Si-B amorphous alloys.The mechanism of HMFA affecting the crystallization microstructure is also discussed in the present work.     

Mechanical alloying of the Fe-Pb system immiscible in the equilibrium state

X-ray diffraction and Mössbauer spectroscopy were used to study the mechanical alloying of the Fe-Pb system, which is immiscible under equilibrium conditions, in a planetary ball mill by the example of an Fe(95)Pb(5) composition. The formation of a supersaturated bcc solid solution of Pb in α-Fe with a limiting concentration of 1.7 at. % Pb has been established. The most fraction of Pb in the mechanically alloyed samples was present as segregates at the boundaries of the nanocrystalline bcc phase. No dissolution of iron in lead has been observed. The mechanism of formation of the supersaturated solid solution includes sequential stages of the formation of a nanostructure in α-Fe, penetration of Pb along α-Fe grain boundaries and its segregation at the boundaries, and the saturation of α-Fe with lead.     

Effect of preannealing on crystallization process of amorphous Sm5Fe80Cu1Si5B3C2.5Zr3.5 alloy

In the view of crystallization activation energy of amorphous alloy,the mechanism of coarse grain in annealed Sm5Fe80Cu1Si5B3C2.5ZR3.5 amorphous alloy was analyzed.It reveals the e4ffect of preannealing on the process crystallization.The results show that preannealing can be used to change the crystallization behavior of the α-Fe phase in the Sm5Fe80Cu1Si5B3C2.5Zr3.5 amorphous alloy,whick is helpful for forming α-Fe phase grains;and it is not large for Sm2Fe17Cx phase.     

两种方法制备纳米晶复相Nd2Fe14B/α-Fe永磁体实验研究

将机械球磨后制备的Nd2Fe14B非晶粉末和α-Fe纳米晶粉末分别采用2种方法制备纳米复相Nd2Fe14B/α-Fe永磁体。第1种方法是直接将其冷压制坯、真空包套和热挤压制备永磁体。第2种方法是先将Nd2Fe14B晶化,然后冷压制坯、真空包套和热挤压制备永磁体。利用TEM、VSM等分析手段对比研究了2种方法制备永磁体的相对密度、微观组织以及磁性能。结果表明:在相同的工艺参数下,第1种方法制备永磁体不仅可以减少工序,而且其制备的永磁体综合性能均优于第2种方法,其制备永磁体的相对密度为98.24%;Nd2Fe14B和α-Fe的晶粒尺寸分别为60和80nm;磁性能达到:Br=0.98T,Hci=305.6kA/m,和(BH)m=89.8kJ/m3。     

PHASE COMPONENT AND CURIE TEMPERATURE OF Nd_4(Fe_(1-x)Cr_x)_(77.5)B_(18.5)ALLOYS

1.IntroductionThenewhard-magneticNdFeBall0yswithlowNdc0ncentration(35at.%)havebeenobtainedbycrystallization0fam0rphous.ibbo.sI1-3].Theirmagneticpr0pertiesatr0omtemperatureareasfollows:coercivityHc=16O-24OkA/m,remanenceB,=1'2-1.25T,andmagneticenergy(BH).ax=64108kJ/m'.ThevaluesofB.and(BH).axaremuchhigherthanth0se0fthewidelyusedanis0tropic(Ba,Sr)Fe12Ol9ferritesandAlNiC0alloys.Inpreyi0uspapers['-'1,wehavereportedthestructuralandmagneticpr0perties.Recentlywestudiedtheinfluenceofthesubstit…     

Fe79Zr9B12和Fe76Zr9B15合金的晶化行为和磁性能

采用单辊快淬法制备Fe79Zr9B12和Fe76Zr9B15非晶合金薄带,并对两合金进行不同温度下热处理。利用差热分析仪(DTA)、X射线衍射仪(XRD)和振动样品磁强计(VSM)研究Fe79Zr9B12合金和Fe76Zr9B15合金的晶化行为和磁性能。结果表明,Fe79Zr9B12合金和Fe76Zr9B15合金的晶化激活能分别为404.42 kJ/mol和370.75 kJ/mol。晶化初期,有α-Mn型相和α-Fe相从Fe79Zr9B12非晶合金基体中析出,Fe23B6型相和α-Fe相从Fe76Zr9B15非晶合金基体中析出。α-Mn型相和Fe23B6型相均为亚稳相,进一步高温热处理后,α-Mn型相转变为α-Fe相,Fe23B6型相转变为α-Fe相、Fe2B相和Fe3B相。Fe79Zr9B12合金的矫顽力(Hc)在600℃退火后突然增大,继续高温退火,Hc下降;Fe76Zr9B15合金的Hc随着退火温度的升高持续增大。两种合金矫顽力随退火温度的变化与退火后合金的微观结构密切相关。