烧结钕铁硼永磁材料

由国家发展计划委员会稀土办公室提出，包头稀土研究院刘国征等人主要负责起草的国家标准GB/T13560-2000《烧结钕铁硼永磁材料》，是对GB/T13560-1992的修订。修订标准规定了烧结钕铁硼永磁材料的主要磁性能和辅助磁性能。主要磁性能包括永磁材料的剩磁(Br)、磁极化强度矫顽力(内禀矫顽力)(Hci)、磁感应强度矫顽力(HcB)、最大磁能积(BHmax)；辅助磁性能包括永磁材料的相对回复磁导率(rec)、剩磁温度系数( (Br))、磁极化强度矫顽力温度系数( (Hci))和居里温度(Tc)。辅助磁性能的典型值为：( (Br))=-0.12%K、测量温度范围为298K~413K…     

NdFeB磁体的薄片铸造法

把按成分配比的NdFeB合金在约1500℃下真空熔融，把熔液倾倒到回转的铜辊上(回转速率约为1m/s)，使急冷凝固，制得约厚0.3mm，长2cm~3cm的薄片状合金，这种合金的结晶组织比用离心铸造法的要细而薄。磁体的基本磁性能由合金的优劣程度决定，日本厂家所供的高性能NdFeB系烧结磁体就是用薄片铸造(SC)法合金生产的。磁材厂家把这种薄片状合金用超细粉碎机粉碎至3m~4m，在磁场下压制、烧结、表面处理、充磁加工成最终产品。 (吴全兴)NdFeB磁体的薄片铸造法@吴全兴     

Sm(CobalFexCu0.088Zr0.025)7.5(x=0-0.30)烧结永磁体的磁性及其高温特性

用粉末冶金艺术制备了Sm(CobalFexCu0.088Zr0.25)7.5(x=0-0.30)烧结磁体，对Fe含量x对磁体的磁性及其高温特性的影响进行了系统研究，随Fe含量的增加，最大磁取积（BH）max和剩磁Br逐渐增加，分别在 x为0．21和0．27时达到了最大值205kJ/m^3和1.055T,然后迅速下降，当x≥0.24时，磁体中开始有FeCo软磁性相析出，破坏了磁体的永磁特性。Fe含量对磁体高温稳定性有巨大的影响，在Fe含量x=0.21时，磁体内禀矫顽力温度系数β为－0.235K,当x=0.07时，β降至－0.14%K(293-723K),制备出有很好的高温稳定性的永磁材料Sm(CbalFe0.07Cu0.088Zr0.025)7.5,在723K时其磁性能力：Br=0.725T,bHc=517kA/m,Hc=764kA/m,(BH)max=95kJ/m^3,B-H退磁曲线保持为直线。     

烧结类钕铁硼永磁材料的生产实践

1前言当代磁王——烧结类钛铁硼（NdFeB）永磁材料，因其具有超高的剩磁、矫顽力和最大磁能积等磁性能，近年来在生产、应用和市场容量中日益增长，并已成为人造永磁体中的主要产品．目前我国烧结类NdFeB永磁材料已走向产业化生产，90年代以来发展十分迅猛．据统计，1992年国内生产NdFeB永磁体产量达到490t，超过美国（380t）居全球第二位，1996年为2600t1997年出口量为2157t在全球范围内其已占主导地位．2钦铁硼永磁材料的生产2．l生产扭值年产量为120t烧结NdFeB永磁体，NdFch的成分为Nd—33％，Fe～66％，B～1．0％．产品规格划BH…     

我国钕铁硼永磁体高速发展

80年代末期，我国烧结钛铁硼永磁体逐步走向工业化生产道路．由于该减体具有较高的剩磁、矫顽力和最大磁能积等优异磁性能，放用途日益广泛，用量猛增，并刺激了烧结钛铁硼的高速发展．卯年代以来，作为“四中之王”的我国烧结钛铁硼永磁体获得更加迅猛的进展．据了解，1992年我国NdFeB磁体产量490t，首次超过美国的正以为29％．1996年产量达2600t，首次超过日本的2400t为8．40．1997年产量3370t，占全球总产量7500t的45％左右，居世界首位，并占有生产该永磁体的主导地位，预计今后将仍然如此．据不完全统计，门如年一1997年我国烧结NdFe…     

烧结Nd—Fe—B磁体的物理和力学性能

烧结Ｎｄ－Ｆｅ－Ｂ磁体的物理和力学性能为在电工产品、仪器仪表和航空航天器件上有效地应用Ｎｄ－Ｆｅ－Ｂ磁体，有必要了解其使用参数。为此对不同成分（１４个成分，包括商业和实验室磁体）的烧结磁体进行了综合研究。给出了这些磁体的物理、力学和电磁性能，供用户选...     

锡对烧结钕铁硼合金热处理行为的影响

研究了Sn，Al，Dy等元素对烧结钕铁硼合金热处理行为的影响。发现Dy和Al的影响很小，含Dy和Al的钕铁硼合金，其热处理行为与三元钕铁硼类似；而Sn对该合金的热处理行为有重大影响。添加少量Sn(约0.1%)就能使合金热处理温度范围变宽，且获得最佳性能的热处理温度移向高温。但是含Sn合金在525～625?℃回火，矫顽力反而比回火前低。X射线衍射发现，这样的合金有明显的α-Fe衍射峰出现。实验表明，仅用晶粒表面光滑化不足以解释合金的热处理行为，还应考虑亚稳相转变对热处理行为的影响。在优化热处理工艺条件下，制得(BH)max=223.7kJ/m3,Hci＞2.11MA/m的Nd27Dy6Fe65.35Al0.4B1.1Sn0.15合金。     

注射成型烧结永磁铁氧体辐射环的制备及脱脂工艺研究

应用粉末注射成型(PIM)烧结技术制备了锶铁氧体辐射环,并对其微观组织、磁性能、脱脂及烧结工艺进行了研究.结果表明,粉末注射成型样品采用溶剂脱脂、热脱脂和烧结工艺处理后,得到的辐向取向永磁环脆性降低,开裂明显减少,环形保持良好.其密度达到4.89 g/cm3,磁性能参量如下:剩余磁感应强度Br为0.398 T,内禀矫顽力Hcj为236.8 kA/m,最大磁能积(BH)max为29.2 kJ/m3,该磁性能水平与传统粉末冶金磁体的磁性能相当,将注射成型烧结技术应用于永磁铁氧体的制备具有很好的应用前景.     

纳米复合WC-6Co粉末的快速烧结

以液相复合-连续还原碳化方法制备的纳米复合WC-6Co粉末为原料，采用放电等离子烧结（SPS），制取了超细硬质合金。利用扫描电镜、维氏硬度仪、洛氏硬度仪、密度测试仪、MTS陶瓷测试系统等，观察烧结体显微结构，测试其硬度、密度、断裂强度、矫顽磁力、磁饱和度。结果表明采用放电等离子烧结获得的烧结体的硬度HVl≥19500MPa，断裂强度TRS≥2800MPa，平均晶粒度150nm～300nm。制备了高强度、高硬度的超细WC-6Co硬质合金。     

某些合金添加剂退火钼丝塑性性能的影响

人们对用于电真空工业的钼丝在退火后的工艺塑性提出了严格的要求:б_B≥87公斤/毫米~2,δ≥18％和K=б_T/б_B≤0.87。由于烧结钼中的杂质含量高,钼丝具有低的塑性性能(δ≤18％和K=1.0),因而不能满足电真空工业的要求。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.