金刚石微粉电镀上砂工艺研究

针对金刚石电镀制品中微粉的上砂工序进行研究。重点对影响金刚石上砂效果的几个关键因素进行了工艺试验,讨论了阴极电流密度、搅拌方式、微粉浓度及尺寸、基体放置方式对沉积效果的影响。认为当阴极电流密度为5 A/dm2,以300 r/m in的速度,采用间歇磁力搅拌方式,对于M36/54金刚石微粉,当装载量为30g/L时,45°角放置基体并定时转动的工艺参数,可使电镀制品获得好的上砂效果。并对实际生产提出了指导性建议。     

电镀工艺参数对金刚石锯丝复合镀层质量影响研究

本文进行了采用复合电镀法制备电镀金刚石锯丝试验,重点分析了上砂与镀层加厚阶段采用不同的阴极电流密度与时间,对锯丝复合镀层外观质量、锯丝表面金刚石磨粒含量和磨粒埋入深度的影响.研究结果表明,当锯丝表面固结粒度为20 μm的金刚石磨粒时,上砂与镀层加厚阶段均可采用2.0A/dm2的阴极电流密度,对应的最佳电镀时间分别为7 ...     

用复合电镀法制造电镀金刚石锯丝的实验研究

固结磨料金刚石线锯切割技术有望在将来广泛地应用于硅晶体等硬脆材料的切割,而高性能的固结磨料金刚石锯丝的研制是此技术发展应用的关键.本文选用以瓦特液为基础的光亮镍镀液,采用复合电镀法试制了电镀金刚石锯丝,制定了锯丝的电镀工艺,分析了上砂电流密度和上砂时间对锯丝表面金刚石磨粒密度和镀层与基体间结合力的影响.结果表明,获得表面磨粒分布均匀、结合力良好的电镀金刚石锯丝的最佳电流密度范围为1.5 A/dm2～2.0 A/dm2,其预镀、上砂与加厚镀时间依次为6 min、8 min～10 min和18 min.     

金刚石线锯悬浮上砂法制作工艺的研究

悬浮上砂法的基本原理是将锯丝基体放置在上砂槽中,槽中的金刚石微粉通过搅拌悬浮在镀液中,通过金属的电沉积将悬浮在镀液中的金刚石微粉固结在芯线基体上.利用悬浮上砂法,以φ0.3 mm的高碳钢丝为基体,选取M20/30～M22/36的金刚石微粉为磨料,选用瓦特型镀液制造金刚石线锯.结果表明:随着上砂电流密度、上砂时间、搅拌速度和金刚石微粉浓度的增加,锯丝表面金刚石微粉的沉积量逐渐增加,当增加到一定值之后不再继续增加.实验得到的最佳的上砂工艺参数为:上砂电流密度5A/dm2,上砂时间4 min,搅拌速度200 r/min,金刚石微粉浓度30 g/L.     

镍—金刚石复合电镀的研究

报导镍-金刚石复合电镀的实验研究结果。实验表明,采用电流密度为2～2.5A/dm~2、温度为45～50℃、pH值为2.8～3.2,搅拌镀液15～20秒停3～4分钟,可获得金刚石微粒含量为8～9Wt％的优质复合镀层;在镀液配方、pH值不变的情况下,电流密度、温度和搅拌间歇时间是影响镀层机械物理性能的主要因素。     

电镀金刚石线锯快速植砂工艺研究

为了提高电镀金刚石线锯的制备效率,通过金刚石微粉表面化学镀镍、钢丝基体磁化处理等方式改进上砂工艺,结合SEM、EDS及高斯计等研究不同工艺因素对电镀线锯的制备效率及耐用度的影响。结果表明:基体磁感应强度、金刚石质量浓度及上砂时间对线锯制备效率及耐用度有重要影响;采用磁化基体制备线锯的最佳上砂工艺参数为:电流密度5 A/dm2、基体磁感应强度0.6mT、上砂槽金刚石质量浓度15g/L、上砂时间30s、温度45℃。采用最佳工艺参数制备线锯的上砂时间缩减为金刚石及钢丝基体没有处理时制备线锯的上砂时间的1/20,制备效率可提高81%,同时还能保持较高的耐用度。      

电源输出形式对电镀金刚石切割线上砂形貌的影响

为研究上砂电源的输出形式对金刚石切割线上砂形貌的影响,使用直径为0.18 mm镀铜高碳钢线为基线,和粒度尺寸为30~40 μm（表面化学镀镍磷合金、增重30%）的金刚石颗粒进行电镀试验。上砂电源的输出形式分别为直流输出、单脉冲输出和双脉冲输出。单脉冲输出时,随着占空比从0.8降到0.2,金刚石颗粒在切割线上的团聚现象逐渐减少,占空比为0.6时上砂效果最佳。双脉冲输出时,随着正向脉冲的开通比从8降到2,金刚石颗粒的团聚现象也逐渐降低,开通比为6时最佳,此时基本没有团聚现象,金刚石分布较均匀。理论分析表明:双脉冲输出的负脉冲对团聚的金刚石有脱附作用,因此能有效抑制团聚现象,同时过于强烈的脱附作用也会降低上砂量。      

液流对电镀金刚石线锯形貌影响

电镀金刚石线锯的上砂过程一直是困扰其生产的关键所在。定性研究涡流和稳流两种不同流动形式对电镀金刚石线锯形貌的影响,并采用不同的电流密度对水平放置的钢线和不同深度竖直放置的钢线分别进行了上砂实验研究。结果发现对于10～20μm的金刚石微粉,如果在涡流的情况下,上砂过程中很难沉积足够的金刚石微粉,这是因为金刚石受到液流的冲刷力影响而难以被电吸附进镀层之中,从而对上砂的过程起到了极大的负面影响;而在稳流的情况下,在不同的电流密度或不同的放置方式的情况下,都能得到金刚石磨粒数量较多的线锯;尤其是竖直放置的情况下,金刚石分布的非常均匀且数量适中,有利于生产高品质的金刚石线锯;同时还发现钢线晃动也会对上砂形貌产生较大的影响,其本质原因可归结于液流作用。     

超声波对电镀金刚石工具制备过程的影响

应用超声波制备了镀层和电镀金刚石工具，测试镀层硬度和金刚石工具的上砂密度，研究结果表明：当电流密度一定时，金刚石工具镀层硬度随超声波功率增强而增加。在金刚石工具制备过程，超声波不适用上砂的全过程。只要金刚石磨粒埋入镀层厚度合适，超声波可以用于金刚石工具的加厚过程，提高工具的制备效率。     

Ni-cBN复合镀层制备工艺参数对性能的影响

采用复合电镀技术在黄铜基体上制备Ni-cBN复合镀层;研究添加和未添加CTAB界面活性剂、镀浴pH值、电流密度、镀浴中cBN微粉浓度、搅拌速度等参数对复合镀层微观组织、显微硬度和耐磨性的影响。结果表明:添加CTAB能显著提高复合镀层耐磨性,并且随着镀层cBN共析量和分散性的增加复合镀层的耐磨性提高;适宜的工艺条件如下:CTAB添加量为0.15 g/L,镀浴pH值为3,电流密度为4 A/dm2,搅拌速度为550 r/min,镀浴中cBN浓度为2.5 g/L。统计分析结果表明:复合电镀参数间相互影响很大,未添加CTAB时,电流密度与搅拌速度相互影响最显著;添加CTAB后,电流密度与pH值的相互影响、镀浴中cBN微粉含量与搅拌速度的相互影响最显著。     

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.