Hydrogen diffusivity in B-doped and B-free ordered Ni3Fe alloys

The hydrogen diffusion coefficient of the ordered Ni₃Fe–B alloys with and without boron additions was measured by a method of the cathodical precharging with hydrogen. The apparent hydrogen diffusion coefficient decreases with increasing the boron concentration doped in the ordered Ni₃Fe alloy. Comparing with the B-free ordered Ni₃Fe alloy, the activation energy of hydrogen diffusion for the ordered B-doped Ni₃Fe alloy increases by as high as 42% when the boron content is sufficient. The doping boron in the Ni₃Fe alloy is effective in reducing the hydrogen diffusion at the grain boundary.     

Development of Fe−12%Cr mechanical-alloyed nano-sized ODS heat-resistant ferritic alloys

The development of mechanical alloying (MA)-oxide dispersion strengthened (ODS) heat-resistant ferritic alloys of Fe?12%Cr with W, Ti and Y₂0₃ additions were carried out. Fe?12%Cr alloys with 3%W, 0.4%Ti and 0.25% Y₂0₃ additions showed a much finer and more uniform dispersion of oxide particles among the alloy system studied. Nano-sized oxides dispersed in the alloys suppress the grain growth during annealing at a high temperature and resulted in the remarkable improvement of creep strength. The oxide phase was identified as a complex oxide type of Y?Ti?O.     

Fe3O4@SiO2磁性复合微球的制备与表征

采用化学共沉淀法制备Fe_3O_4颗粒,在其制备过程中控制Fe_3O_4核的长大时间,加入油酸钠作为表面修饰剂来控制Fe_3O_4核的尺寸,然后加入正硅酸乙酯(TEOS)生成纳米级Fe_3O_4@SiO_2复合纳米粒子和亚微米级Fe_3O_4@SiO_2复合微球。通过X射线衍射、透射电镜、能谱分析和红外光谱分析证实Fe_3O_4颗粒表面包覆有SiO_2,并研究了复合粒子的形貌和成分组成,然后进行了磁性能分析。结果表明,Fe_3O_4纳米颗粒、Fe_3O_4@SiO_2复合纳米粒子和亚微米级Fe_3O_4@SiO_2复合微球的饱和磁化强度分别为79.95、34.85和61.51 A·m2/kg,对应的剩磁分别为1.73、1.05和3.07 A·m2/kg,矫顽力分别为1083、755和2002 A/m,亚微米级复合微球的剩磁和矫顽力都显著增大。     

添加元素Dy对Nd—Fe—B永磁合金性能的影响

由于氢化制粉制备的ＮｄＦｅＢ粉末制品烧结时磁体中的晶粒异常长大,使合金的矫顽力降低。通过在ＮｄＦｅＢ合金中加入少量Ｄｙ２Ｏ３,能有效地抑制合金高温烧结时的晶粒长大,增加了各向异性很高的（Ｎｄ,Ｄｙ）２Ｆｅ１４Ｂ相,从而使合金的矫顽力得到提高,当Ｄｙ的加入量超过（摩尔分数）４％时,Ｄｙ在富Ｎｄ相晶界中分布比在基体相Ｎｄ２Ｆｅ１４Ｂ中高。     

Corrosion of nickel with small alloy additions of Si,Fe, and Mn in SO2+O2/SO3 at 700°C

The corrosion of nickel with alloy additions of Si, Fe, and/or Mn up to 4 wt% has been studied in SO ₂+O₂/SO₃ at 700°C. All alloy additions greatly improve the corrosion resistance of nickel in oxygen-rich atmospheres (O₂ with about 4% SO₂); the best improvements are achieved with Si, Fe+Si, and Fe+Mn+Si additions. High-purity nickel corrodes rapidly under these conditions; the scale then consists of NiO+Ni₃S₂, and the sulfide forms a three-dimensional network along the grain boundaries of the NiO grains and serves as the diffusion path for rapid outward migration of nickel. From studies of the microstructure and distribution of the alloying elements in the protective scales, it is proposed that the alloying additions exert their beneficial effects by accumulating/segregating at the grain boundaries of NiO (e.g., as silicates) and thereby influence the wetting characteristics and disrupt the sulfide network.     

立方碳化物和La添加剂对WC-Co合金中WC晶粒形貌以及合金硬度与韧性的影响(英文)

研究了立方碳化物 Cr3C2、VC 以及稀土 La 添加剂对 WC-Co 合金中 WC 晶粒形貌以及合金硬度与韧性的影响。为了强化烧结过程中 WC 晶粒生长的驱动力,采用具有高烧结活性的纳米 W 和纳米 C 为原料。为了获得合金中 WC 晶粒的三维形貌,采用扫描电镜直接观察合金烧结体的自然表面。结果表明,合金添加剂对WC 晶粒形貌及其粒度分布特征以及合金的硬度与韧性有较大影响。由于均质三角棱柱形板状 WC 晶粒的形成,WC-10Co-0.6Cr3C2-0.06La2O3 合金具有极佳的硬度与韧性组合。讨论了合金中 WC 晶粒形貌的调控机制以及合金中 WC 晶粒形貌特征对合金性能的影响。     

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.     

Microstructural evolution of NiFe2O4-10NiO powder prepared by high temperature solid state reaction

1 Introduction The development of inert anode materials for aluminium production has gained considerable attention in recent years[1,2]. The significance of such anodes is the ability to produce environment-friendly O2 gas during electrolysis instead of g…     

Atomistic simulation of ∑3 (111) grain boundary fracture in tungsten containing various impurities

The effect of various impurities and micro-alloying additions (B, N, C, O, Al, Si, S and P) on the intrinsic resistance of the ∑3 (111) grain boundary in tungsten has been investigated using the molecular dynamics simulation. The atomic interactions have been accounted for through the use of Finnis-Sinclair interatomic potentials. The fracture resistance of the grain boundary has been characterized by computing, in each case, the ideal work of grain boundary separation, the mode I stress intensity factor and the Eshelby's F₁ conservation integral at the onset of crack propagation. The results obtained suggest that pure tungsten is relatively resistant to grain boundary decohesion and that this resistance is further enhanced by the presence of B, C and N. Elements such as O, Al and Si however, have a relatively minor effect on the cohesion strength of the ∑3 (111) grain boundary. In sharp contrast, S and P greatly reduce this strength making tungsten quite brittle. These findings have been correlated with the effect of the impurity atoms on material evolution at the crack tip.     

Al-7%Si-Mg铸造铝合金添加Ce与Sr元素后初生α（Al）枝晶的动力学形核

利用差示量热法（DSC）和扫描电镜研究 Al-7%Si-Mg 亚共晶铸造铝合金添加 Ce 与 Sr 元素后初生α（Al）枝晶的动力学形核。根据DSC结果计算初生α（Al）相的激活能和形核功。结果表明,合金中添加Ce与Sr元素后,激活能和形核功降低,形核率增加;同时,初生α（Al）晶粒细化,其形核温度降低。讨论添加Ce与Sr元素对Al-7%Si-Mg亚共晶铸造铝合金初生α（Al）枝晶动力学形核的影响。     

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.     

Effect of Zr on the Oxidation Properties of Fe3Al Intermetallic Compound

This review is concerned with the effect of the addition of zirconium as a third element on the heat-resisting properties of Fe3Al intermetallic compounds and explains their high-temperature oxidation mechanism. The Fe3Al and Fe3Al-0.05Zr specimens were isothermally oxidized in the temperature range of 1173～1473 K in synthetic air for 100 h. The formation of the alumina layer approximately obeyed the parabolic rate law, with the exception of short initial stage. The parabolic rate constant values for the Zr-doped Fe3Al decreased at all tested temperatures. Fe3Al revealed massive spallation, whereas Fe3Al-Zr produced a fiat, adherent oxide layer. The microstructure investigations of the alumina scales grown thermally on the Fe3Al-Zr alloy by means of SEM-EDS showed that they were 1.5～2 μm thick and consisted of a small inner columnar layer and an equiaxed outer grain layer. Additionally, very fine (50～150 um) oxide particles rich in Zr were found across the alumina scales. The addition of Zr significantly affected the oxidation behavior of Fe3Al by improving the adherence of the α-Al2O3 scale. TEM-SAD investigations of the alumina scales on samples prepared using the FIB (Focused Ion Beam) method confirmed the presence of small tetragonal zirconia grains near the scale/gas and alloy/scale interfaces, most of which were formed along alumina grain boundaries(gbs). Zr gb-segregation was found using HRTEM. The role of preferential formation of zirconium oxide along the alumina scale grain boundaries and the effect of Zr gb-segregation on oxidation and scale growth mechanisms were analyzed by means of two-stage oxidation experiments using 16O2/18O2. The SIMS oxygen isotope profiles for the Fe3Al-Zr alloy oxidized at 1373 K, after two-stage oxidation experiments, revealed that oxygen anion diffusion is predominant compared to that of aluminum cation diffusion.     

Large strain deformation of Ni3Al+B: Part II. Microstructure and texture evolution during recrystallization

The microstructure evolution and texture development of the intermetallic compound Ni₇₆Al₂₄, doped with minor additions of boron, was investigated during annealing subsequent to cold-rolling. Upon annealing of cold-rolled specimens, a hardness increase prior to recrystallization was observed. This is attributed to a relaxation process of the dislocation cores during annealing. Recrystallization proceeded with very different kinetics locally and a very small recrystallized grain size was obtained. From grain growth kinetics, the activation energy for grain boundary motion was found to be close to the activation energy for self-diffusion of Ni in Ni₃Al. The recrystallization texture was almost random. However, three texture components could be invariably recognized ({013}100, {012}021 and {112}294). They are related by special orientation relationships to the brass rolling orientation. A high frequency of annealing twins occurred in the recrystallized microstructure. The misorientation distribution function (MODF) shows a preference of certain low Σ boundaries, namely small-angle boundaries (Σ1) and twins (Σ3).     

Ca-Dy2O3-Fe体系反应的动力学研究

分析了Ｃａ－Ｄｙ２Ｏ３－Ｆｅ体系高温还原－扩散制备ＤｙＦｅ２热力学可能性,应用收缩核模型确定扩散是该体系反应的控制步骤,并进行了ＸＲＤ,ＥＤＸ与ＳＥＭ分析,得知在高温下可用Ｃａ还原Ｄｙ２Ｏ３生成Ｄｙ,Ｄｙ向Ｆｅ中扩散生成ＤｙＦｅ２,同时求得ＤｙＦｅ２的表观活化能为２１０ｋＪ／ｍｏｌ。     

Preparation and mechanical properties of Fe_3Al/Al_2O_3 nano-/micro-composite

1　INTRODUCTIONAlumina(Al2 O3)ceramicsareoftenconsideredforstructuralapplications,duetotheirpropertiesofhighhardness ,chemicalandwearresistanceandgoodmechanicalpropertiesatroomandhightemperature .Thewellknownlimitationfortheseceramics ,how ever ,istheverylowtoughness .Recentstudieshaveshownsignificantimprovementsinmechanicalprop erties ,includingtoughness ,byaddingductilesecondphaseparticles ,suchasNi,Al,MoandCu[14 ] .Anincreaseof 80 % 333%inthefracturetoughnesshasbeenreportedforAl2 O3…     

Microstructure,corrosion behavior,and surface mechanical properties of Fe oxide coatings on biomedical ZK60 Mg alloy

The Mg‐5.5Zn‐0.6Zr (in wt%, ZK60) alloy has been surface modified by dual Fe&O ion implantation and deposition (II&D) under different O₂ fluxes from 0 to 40 sccm. The microstructure is investigated by glancing angle X‐ray diffraction, atomic force microscope, and scanning electron microscopy. The results show that the modified layers, with a gradient microstructure of outer deposition region and inner implantation region, are composed of α‐Fe + Fe&Mg mixture, FeO/Fe‐rich oxide + Fe&Mg mixture, and α‐Fe₂O₃/Fe‐rich oxide + Fe&Mg mixture for 0, 10, and 40 sccm O₂ fluxes, respectively. The electrochemical and immersion tests in 37°C Hank's solution indicate an improvement in corrosion behavior under 0 and 10 sccm O₂ fluxes, but a deterioration in corrosion resistance under 40 sccm O₂ flux. In addition, the nanoindentation tests suggest that the dual Fe&O II&D simultaneously enhances the surface hardness and elastic modulus due to the formation of Fe and its oxide coatings.     

Structural macrokinetics of synthesizing ZnFe2O4 by mechanical ball milling

Powder mixtures of Fe2O3 and ZnO were milled in a high-energy planetary ball mill to synthesize ZnFe2O4 and X-ray powder diffractometry was used to obtain the relative content of phases,crystallite size and microstrain of both Fe2O3 and ZnFe2O4. The lattice constants of Fe2O3 were obtained by cell refinement method.The macrokinetics and the structure evolution of matters were studied and the results show that the dynamics process of mechanochemical synthesis of ZnFe2O4 fits Avrami-Erofe’ev model and is controlled by a nucleation-growth mechanism,and the structural macrokinetics theory in combustion synthesis research area could be used to describe the kinetic process as well.     

过量Fe2O3对铝热法制备微纳结构316L奥氏体不锈钢组织和拉伸性能的影响

不锈钢结构和成分的调节对获得良好综合性能至关重要。为了使铝热反应完全、降低316L奥氏体不锈钢(ASSs)中残余Al的含量,在反应粉体中加入了不同过量分数的Fe2O3粉末,详细分析了过量Fe₂O₃对316L ASSs微纳米组织和拉伸性能的影响。结果表明,随着Fe2O3过量分数的增加,铁素体相的体积分数显著降低,而纳米晶的体积分数由87.4%提高到了93.4%,平均晶粒尺寸由32 nm降低到了22 nm。对比分析表明,铝热法制备316L ASSs的最佳工艺参数为添加过量分数5.0%的Fe₂O₃,在该条件下制备的单相奥氏体钢,其抗拉强度为573.92 MPa,屈服强度为340.12 MPa,延伸率为4.68%。     

Effect of additive on corrosion resistance of NiFe2O4 ceramics as inert anodes

In order to improve the corrosion resistance of NiFe2O4 ceramics as inert anode, additive V2O5 was added to raw materials NiO and Fe2O3. The inert anodes of nickel-ferrite ceramics were prepared by powder metaUurgic method and the static corrosion rate in Na3AlF6-Al2O3 was determined by mass loss measurement. The effect of V2O5 on sintering property and corrosion resistance was studied. The results show that V2O5 can promote the grain to develop completely and improve sintering property. EDS results show the reaction product Ni2FeVO6 distributes along the grain boundary. The corrosion tests show that V2O5 is beneficial to improving corrosion resistance remarkably. The reasons that V2O5 can improve the corrosion resistance must be V2O5 promoting the gains to develop completely and Ni2FeVO6 distributes along the grain boundary. The stable structure can control the chemical dissolution of ceramics anode and the reinforced grain boundary can control the grain-boundary corrosion rate.     

Influence of flux composition on microstructure and oxygen content of low carbon steel weldments in submerged arc welding

This study has been conducted to evaluate the influence of flux composition on the microstructure and oxygen content of the low carbon steel weldments using developed agglomerated fluxes.Ca_F2,FeMn and NiO were added to the CaO-SiO_2-Al_2O_3 base fluxes in the varying amount of 2%-8% to examine the various elements transferred to the weldments.The microstructure obtained was a mixture of pearlite and ferrite contents.This study reveals that CaF_2 and Fe Mn both are having significant effect on pearlite percentage while CaF_2 and NiO are significant for oxygen transfer in the welds.The interaction effects of CaF_2 and Fe Mn and CaF_2 and Ni O are also significant to the microstructure of the welds.The fluxes were designed using response surface methodology( RSM) and were developed by agglomeration technique.