真空热处理下沥青基碳微球向石墨化球转变的研究

本文以脱油沥青的高附加值利用为研究目的,采用化学气相沉积和真空热处理相结合的方法,宏量制备得到粒度均一、高的石墨化程度和高的热稳定性石墨微球(Graphitic Spheres,GSs).通过SEM、HRTEM、XRD和TGA等测试手段对比碳微球和石墨碳球,高温热处理得到的碳球石墨化程度高,热稳定性好.在热动力作用下,无序结构的碳微球结构逐步向有序的石墨碳结构过渡,形成了石墨球.     

低温热处理对球铁中不同原始石墨组织的影响

利用原料的遗传性制成化学成分基本相同但组织不同的球墨铸铁,研究了低温热处理对球铁中不同原始石墨组织的影响.结果表明,经低温热处理后,铸态石墨化程度低且球化效果较差的石墨组织,球化率和球化级别显著提高,石墨的平均球径增加;铸态石墨化程度高且球化效果比较理想的石墨组织中出现了部分点状石墨,石墨球的平均球径减小,且点状石墨群和球状石墨群有规律地交替分布,而石墨的球化等级和球化率没有明显变化.     

石墨-FeNi核-壳结构复合微球的制备

以硫酸亚铁、硫酸镍、碳酸钠和石墨微球为主要原料，利用非均相成核工艺制备出水合氧化铁和碱式碳酸镍均匀包覆石墨的前驱体微球：通过对前驱体进行热还原处理得到了晶粒约为50nm的γ-FeNi合金颗粒层包覆石墨的产物微球。利用SEM，EDS，XRD对前驱体和产物的形貌、成分、物相分别进行了表征，并利用TG／DSC对前驱体热分解过程进行了分析。通过研究，得出了制备这种核．壳结构复合微球的优化工艺参数。     

铸态球铁的生产控制

影响铸态球铁生产稳定性的因素很多，我们通过铁素体、珠光体基体球铁的生产，得到了一定的经验。１原材料的选择１１炉料的选择生铁应高碳低硅，低硫低磷。地方生铁应慎用，因五元素正常而有微量元素干扰球化，导致球化不良，而一般工厂又化验不出。即使有些生铁合较高铜、钼有利于珠光体球铁生产，但当生产球铁种类较多时不便管理。另外，对石墨片粗大、渣气孔较多的生铁尽量不用。回炉铁杜绝使用球化不良的废铸件，废钢应是成分明确的无锈碳素废钢。１．２焦炭的选择焦炭要求高固定碳、低硫。我们用山西临汾铸造焦，固定碳在８７％以上，…     

低蠕化率蠕铁与球化不良及衰退球铁的区别

详细介绍了低蠕化率蠕铁、球化不良球铁及球化衰退球铁的区别。金相组织的区别是:低蠕化率蠕铁的球状石墨圆整,蠕虫状石墨粗短,只有极少量的团絮状石墨,没有片状石墨,基体组织细密;球化衰退的球铁石墨形态恶化,开花状石墨和团絮状石墨较多,严重时有片状石墨,组织粗大;球化良好的铸铁,球墨圆整,极少团絮状和蠕虫状石墨,没有片状石墨,组织细密。力学性能的区别是:球化衰退球铁的力学性能已明显下降,低蠕化率蠕铁的力学性能则远高于规定要求,如果采用适当的热处理方法,在冷热交变环境下服役能显示优异性能,因此,不能笼统地将其判为废品。     

低合金球墨铸铁磨球的研制及应用

对碳、硅含量及球化剂量、孕育剂量的控制和热处理工艺的研究,获得了在马氏体基体上同时分布着碳化物和石墨球的球墨铸铁,用其制造的磨球具有高的耐磨性,且价格便宜。     

核壳结构石墨/磁性纳米合金复合微球的制备

以硫酸亚铁、硝酸钴、硫酸镍、碳酸钠和石墨微球为主要原料,利用非均相沉淀工艺分别制备出水合氧化铁、碱式碳酸钴和碱式碳酸镍包裹石墨微球的前驱体复合微球;然后将前驱体复合微球于600℃热还原处理2 h,分别得到了钴铁、铁镍和钴镍磁性纳米合金颗粒层均匀包裹石墨微球的粉体材料.利用SEM,EDS,XRD对前驱体复合微球和核壳结构石墨/磁性纳米合金复合微球的形貌、成分、物相进行了表征,利用VSM对核壳结构石墨/磁性纳米合金复合微球的磁性能进行了研究.这些核壳结构复合微球的磁性合金颗粒层分别由晶粒为37.9 nm的Co0.5Fe0.5、38.5 nm的Fe0.5Ni0.5和38.2 nm的Co0.5Ni0.5组成,相应的矫顽力分别为36676,20972,16894A/m.     

稀土镁韧性球铁熔模铸造工艺初探

氧化铝———铝矾土高强型壳,由于灼减度小,模壳密度小,强度高,热稳定性好,型腔光滑。同时注意球铁水化学成份即硅要低,残留镁及残留稀土量高,浇注温度１ ３００ ℃～１ ３１０ ℃,球化剂量１ ．４ ％ ,浇注后石墨飘浮、球化及孕育衰退消除,球化级别及机械性能均不减低。     

球墨铸铁的石墨球数及其影响因素

球铁生产中希望获得球形圆整、分布均匀、球径较小和数量较多的石墨球。国标GB9441－88“’对球化级别（球化率）和石墨大小作了分级，但没有石墨球数的评定级别。美国铸造师学会（AFS）编写的《球墨铸铁金相图谱）t”（以下简称AFS图谱）中把石墨球数由25个／mm’到300个／mm’，分为7个级别。在球化良好和石墨分布均匀的球墨铸铁中，石墨球数与石墨大小（球径）有一近似的对应关系，如表1。由表1可见，用石墨球数来评价球铁组织中石墨的均匀程度要比用石墨大小（或球径）作评价参数，更为详实和精确。目前，国内对石墨球数的研究较少…     

商品化石墨作为聚合物锂离子电池负极材料的性能表征

采用商品化中间相碳微球(MCMB)及人造石墨与中间相碳微球的混合体作为聚合物锂离子电池的负极材料,通过SEM、XRD对比研究了两种负极材料电化学循环前后的微观形貌和相结构,测试了两种聚合物锂离子电池的倍率放电性能和循环寿命,并通过交流阻抗谱分析了两种负极材料的电化学性能差异.结果表明:掺入人造石墨后,中间相碳微球的平均粒径和比表面积增大,电化学循环200次后的晶面间距减小、石墨化度增大,倍率放电性能降低,电荷转移电阻及锂离子扩散阻抗均增大,循环性能得到较大提高.     

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.     

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.     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.