提高SiC陶瓷烧结用真空中频感应炉加热性能的试验研究

本文对SiC陶瓷加热用ZG-10 1700℃真空感应烧结炉进行了改进，以提高其加热性能。选择石墨作为发热体，ZrO2空心球作保温材料，对感应线圈、石墨坩锅尺寸、透入深度等进行了设计优化。试验结果表明，改进后的真空感应炉运行4个小时后，即可由常温升至2400℃，短时可达2500℃，并且发热体、保温材料无明显损坏。本研究对于提高真空中频感应炉的加热性能及满足SiC工程陶瓷制品烧结的一些特殊要求有重要意义。     

采用TiH_2预处理的SiC陶瓷柱阵列增强/高铬铸铁复合材料界面与耐磨性能（英文）

利用TiH2粉末膏剂涂覆和在真空下1000或1400℃保温20 min的预处理工艺对反应烧结SiC陶瓷柱进行了表面预处理,再将预处理好的SiC陶瓷柱固定在石墨板上,随后采用金属浇铸工艺制备了一种具有高度陶瓷增强体宏观均匀性、可靠性和可设计性的SiC陶瓷柱阵列增强高铬铸铁复合材料。陶瓷涂层和复合材料界面分析表明:1400℃为较优的SiC表面预处理温度,预处理后SiC表面形成一层可靠的金属性复合层。该复合层在高温浇注过程中不会被溶解,可有效抑制高铬铸铁与SiC陶瓷的界面反应,从而形成无脱层、优良的复合材料陶瓷/金属磨损界面。与该复合材料的金属基体相比,由于SiC陶瓷柱的有效添加,经表面处理后不同陶瓷含量的SiC/高铬铸铁复合材料的耐磨性能均显著提高。     

Interface and Wear Resistance of SiC Ceramic Column Grid Array Reinforced High-Chromium Cast Iron Composite Pretreated with TiH2

利用TiH2粉末膏剂涂覆和在真空下1000或1400℃保温20 min的预处理工艺对反应烧结SiC陶瓷柱进行了表面预处理,再将预处理好的SiC陶瓷柱固定在石墨板上,随后采用金属浇铸工艺制备了一种具有高度陶瓷增强体宏观均匀性、可靠性和可设计性的SiC陶瓷柱阵列增强高铬铸铁复合材料。陶瓷涂层和复合材料界面分析表明:1400℃为较优的SiC表面预处理温度,预处理后SiC表面形成一层可靠的金属性复合层。该复合层在高温浇注过程中不会被溶解,可有效抑制高铬铸铁与SiC陶瓷的界面反应,从而形成无脱层、优良的复合材料陶瓷/金属磨损界面。与该复合材料的金属基体相比,由于SiC陶瓷柱的有效添加,经表面处理后不同陶瓷含量的SiC/高铬铸铁复合材料的耐磨性能均显著提高。     

Ni基高温钎料连接SiC陶瓷的微观结构和力学性能

采用低成本的Ni基高温钎料对SiC陶瓷进行了钎焊连接，通过扫描电镜、能谱分析、透射电镜等测试手段分析了接头的微观结构和物相组成，系统研究了不同钎焊温度和保温时间对SiC/SiC接头力学性能及微观结构的影响规律，分析了不同钎焊工艺参数下制备的SiC/SiC接头断口形貌，阐明了接头宏观力学性能与微观结构之间的对应关系。最后，评价了SiC/SiC接头的高温力学性能。结果表明，SiC/SiC接头由反应区、中心区和基体区3个区域组成，其中反应区主由Ni₂Si和不同数量的石墨组成；而中心区主要由复杂碳化物Ni₃Mo₃C和Ni₂Si组成。提高钎焊温度和延长保温时间石墨能够使SiC/SiC接头的反应区厚度增加，生成石墨相的数量也逐渐增多并发生团簇聚集的现象，显著影响了接头的抗弯强度。在1 300℃，40 min条件下，反应区的厚度和石墨的形成量是适宜的，SiC/SiC接头的室温四点抗弯强度最大，达到179 MPa±7 MPa。同时，该接头还具有良好的高温稳定性，在700℃高温下仍能有97.2%的强度保持率，在高温环...     

温度、惰性填料对先驱体硅树脂高温连接 Cf/SiC陶瓷基复合材料的影响

对先驱体硅树脂高温(800℃～1 400℃)转化陶瓷结合层连接石墨、陶瓷SiC及Cf/SiC复合材料进行了研究,着重对硅树脂固化裂解过程、裂解温度及惰性填料对连接性能的影响进行了探讨.结果表明,硅树脂的交联固化主要是通过消耗Si-OH来完成.对于石墨、SiC的连接,1200℃是较佳的处理温度,而对于Cf/SiC则最佳的处理温度为1 400℃.加入5%惰性填料SiC可以提高硅树脂对Cf/SiC复合材料的连接性能.     

石墨上化学气相沉积SiC组织特征与性能

利用压汞法、SEM和EDS等分析手段对石墨及化学气相沉积SiC组织结构进行了研究。石墨试样的比表面测试显示：经2200℃高温处理石墨试样的比表面积较未处理试样增大了近34％。石墨试样的孔径分布显示：高温处理石墨试样的孔径分布在〈10nm和〉200nm有所增加，而界于两者之间的中型孔径分布略有降低，从而证明了热处理中大量原子发生一定范围的重排。SEM和EDS分析表明，高温处理过的石墨沉积SiC具有CVI结构特征；经过高温处理的石墨SiC沉积呈CVI特征，而未经高温处理石墨沉积的SiC呈典型CVD特征。对CVDSiC／graphite再经1600℃处理，对强度影响不大。     

网状钨丝炉发热体的焊接

我厂试制了一台大型真空钨丝电阻炉,该炉钨丝网发热体及其部件采用焊接方法连接而成。要求所有焊缝能够经受220℃高温下使用的要求,因此焊接质量的好坏直接影响发热体的使用寿命。发热体由六片已组装的钨丝网,其一端通过内外两只钨圈与电极板和加强板焊接而成(图1、图2)。发热体采用分片组装和总装,分     

硅掺杂碳复合靶材的制备研究及溅射膜层生长形式分析

以石墨、碳化硅、硅粉体为原料，采用预处理工艺得到复合原料粉体，热压烧结制备C/Si 80/20 at%靶材。将制备的靶材在不同基片上溅射镀膜，分析薄膜的形貌及其生长模式。通过扫描电镜分析微观形貌、四探针测试电阻率、XRD结合拉曼光谱分析晶体结构，结果如下：（1）石墨和硅粉球磨混合48h可获得Si元素均匀分布的C/Si复合粉体；该粉体在1900 ℃下真空热处理时，C/Si通过互扩散生成等轴晶3C-SiC；（2）不同粒径的β-SiC粉体在1900 ℃真空热处理时，颈部生长速率和晶体结构转变存在显著差异。在高温下，纳米β-SiC粉体蒸汽压高，颈部增长速率快，通过蒸发-凝聚再结晶后可获得球形度良好的3C-SiC微米颗粒。（3）以C/Si/SiC 70/10/10 at%粉体为原料，采用球磨和高温真空热处理得到预处理粉体并热压制备C/Si 80/20 at%靶材，结果表明：与C/SiC 60/20 at%二元组分体系相比，三元组分预处理粉体制备靶材的均匀性好，平均电阻率3.9 mohm·cm，极差0.59，密度2.34 g/cm3，石墨化度0.17, 石墨晶体完整性好。（4）将制备的C/Si 80/20at%靶材分别在玻璃、硅片以及陶瓷基片上磁控溅射制备类金刚石薄膜，结果发现：在Si基体表面薄膜呈纵向生长模式，膜层微粒小于20 nm；在玻璃基体表面膜层呈层状生长模式且结合紧密；在陶瓷基体表面薄膜呈片状生长模式，膜层由微米级颗粒结合组成，与陶瓷基体的微观组织相似。     

近净成形制备SiC/Al复合材料Ⅰ:SiC预成形坯的制备

以微米级的碳化硅粉和石墨粉为原料,采用氧化结合法制备出不同孔隙含量的、适合液态铝无压渗透的SiC预成形坯。研究SiC多孔陶瓷的低温烧结机理和石墨添加量对SiC陶瓷骨架烧结密度和尺寸变化的影响。结果表明：在1 100℃烧结时,碳化硅和石墨粉同时发生氧化反应;SiC氧化产生的结晶态SiO2膜将SiC粉体粘结成陶瓷骨架,石墨氧化去除后形成孔隙;SiC粉体间本征孔隙和石墨去除后留下的孔隙构成三维互连通状态;因SiC氧化导致陶瓷骨架产生4%左右的线膨胀,但坯体不发生形状改变;通过调整石墨含量,能获得孔隙率从0.47-0.63的SiC陶瓷骨架。     

Al4SiC4陶瓷的高温氧化行为

从高温氧化动力学、组织的微观进化及高温氧化机理3部分对Al4SiC4陶瓷在1200℃-1700℃的高温氧化行为进行了系统的研究。研究结果表明，Al4SiC4陶瓷具有优异的高温抗氧化性能。氧化动力学符合抛物线规律，其氧化活化能经计算为220kJ／mol。XRD及SEM研究结果表明：Al4SiC4陶瓷在1200～1500℃的氧化表面物相为Al2O3和铝硅酸盐玻璃；而高温氧化表面（1600℃～1700℃）的物相由Al2O3，莫来石和铝硅酸盐玻璃构成。由氧化试样横截面观察得知氧化层按其特征的不同分为3个部分：具有较多细小尺寸孔洞的反应层；具有较大尺寸孔洞的中间层和致密的外氧化层。在高温抗氧化机理部分中首先从热力学上计算了氧化过程中各反应的生成焓和吉布斯自由能；然后对高温氧化过程进行了推理和分析；最后根据上述试验及推理结果建立了Al4SiC4陶瓷的高温抗氧化模型。     

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.     

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.     

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。     

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).     

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.     

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.