高炉冷却壁冷却水管内液固两相流强化传热实验研究

针对高炉冷却壁管内污垢沉积而导致传热效率低的问题,提出在高炉冷却壁管内加入固相颗粒以形成液固两相流,在防止污垢的沉积及清洗污垢的同时,增加流体的扰动强化管内对流传热.对液固两相流和单相流的传热性能进行了对比实验.结果表明,由于固相颗粒的扰动和剪切效应,不仅可以强化管内传热,而且也可以在线清洗管内污垢,在流速为2 m/s,固相体积分数为3.5%～5.0%、固相粒径为2～3 mm的范围内,与单相流相比,液固两相流的传热系数提高了20%～45%.实验结果为液固两相流的工业应用提供了基础.     

纳米碳化钛颗粒增强锌基复合材料的阻尼性能研究

为了提高锌基合金的阻尼性能,研究了添加纳米TiC颗粒对ZA合金阻尼性能的影响.结果表明,添加纳米TiC颗粒可以将锌基复合材料的阻尼比提高25％～35％,从而降低受迫振动的振幅,即可达到减振降噪的作用.这证明纳米碳化钛颗粒增强锌基复合材料在高速、高效、高自动化并需减振降噪的机械设备中有良好的应用前景.     

水基纳米氮化钛流体摩擦学性能研究

将纳米氮化钛颗粒分散到水基础液中,加入适量的分散剂,采用两步法可制备出具有良好分散稳定的水基纳米氮化钛流体。在此基础上,采用单一变量法,用M-200磨损试验机研究了这种纳米流体对钢环的磨损性能,并对其摩擦润滑机理进行了分析。结果表明:摩擦系数与磨损量随负荷的增加表现出先减小后增大的趋势,并且当质量分数为1%的PVP与CTMAB混合液作为分散剂、粒径为20nm且质量分数为1%的氮化钛颗粒、分散介质为去离子水时表现出最佳的润滑性能。     

电沉积耐磨减摩纳米复合镀层的研究进展

纳米复合镀层比常规镀层具有更高的硬度和更加优良的摩擦学性能.评述了纳米复合镀层的电沉积工艺,包括纳米颗粒前处理、纳米颗粒添加量、电流、镀液pH值、镀液温度和搅拌方式等对镀层中纳米颗粒含量、镀层表面形貌及微观结构的影响,对纳米复合镀层摩擦学性能以及纳米颗粒耐磨减摩机理的研究进行了综述.     

纳米SiC颗粒对微米Ni-SiC复合镀层性能的影响

采用双脉冲复合电镀技术,在瓦特型镀液中,制备了含微/纳米SiC颗粒的Ni基复合镀层,研究镀液中纳米SiC添加量对复合镀层微观形貌、摩擦性能和抗氧化性能的影响。结果表明:在SiC颗粒(5μm)浓度为10 g/L的镀液中,添加纳米SiC和Ni-SiC复合镀层镍择优取向由晶面(200)转变为晶面(111);当SiC(40μm)浓度为4.0 g/L时,复合镀层显微硬度最大,为456 HV;复合镀层摩擦因数最小,平均值为0.28,为微米复合镀层的1/2;经900℃氧化100 h后,氧化质量增加为6.025 mg/cm2,为微米复合镀层的1/3。     

结晶器铜板表面耐磨纳米复合镀层的制备及性能

目的提高连铸坯质量,延长结晶器的服役时间,节约铜资源。方法采用纳米复合镀技术在结晶器铜板表面制备了Ni/Al_2O_3纳米复合镀层,并通过扫描电镜(SEM)观察了复合镀层表面形貌。采用单因素变量法研究了镀液中纳米Al_2O_3添加量、阴极电流密度及镀液温度等对纳米复合镀层显微硬度的影响。对结晶器铜板表面的纯Ni镀层和纳米复合镀层进行了摩擦磨损实验。结果在结晶器铜板表面制备出了高硬度、耐磨损的纳米复合镀层。随着镀液中纳米颗粒添加量的增加,镀层的硬度先升高后降低,且当纳米颗粒添加量为40 g/L时,复合镀层的显微硬度达到最大值384HV。因镀液中纳米颗粒的存在,随着电流密度和镀液温度的变化,纳米复合镀层的硬度变化不大。在相同的摩擦磨损条件下,纳米复合镀层和纯Ni镀层的摩擦系数分别约为0.41和0.7,纳米复合镀层的磨损量约为纯Ni镀层的1/2。结论在Ni基镀层中加入纳米Al_2O_3材料,能显著地提高复合镀层的硬度、耐磨损性能。     

非晶态Ni-P合金与纳米Al2O3微粒复合镀层的制备

利用化学镀技术,制备了非晶态Ni-P合金基纳米Al2O3复合镀层,研究了纳米Al2O3微粒的加入量、加入方式以及搅拌方式等对复合镀层组织和形貌的影响.结果表明,纳米Al2O3在加入到镀液中以前,应先选用适当的表面活性剂和分散介质制成单分散添加液,然后再加到镀槽中才可保证纳米粒子在镀层中的均匀弥散分布,在超声振动搅拌方式下,镀液中只需加入1g/L纳米Al2O3,即可得到颗粒细小、分散均匀的非晶态Ni-P合金基纳米Al2O3的复合镀层.     

纳米生物润滑剂微量润滑磨削性能研究进展

微量润滑是针对浇注式和干磨削技术缺陷的理想替代方案，为了满足高温高压边界条件下磨削区抗磨减摩与强化换热需求，进行了纳米生物润滑剂作为微量润滑的雾化介质探索性研究。然而，由于纳米生物润滑剂的理化特性与磨削性能之间映射关系尚不清晰，纳米生物润滑剂作为冷却润滑介质在磨削中的应用仍然面临着严峻的挑战。为解决上述需求，本文基于摩擦学、传热学和工件表面完整性对纳米生物润滑剂的磨削性能进行综合性评估。首先，从基液和纳米添加相的角度阐述了纳米生物润滑剂的理化特性。其次，结合纳米生物润滑剂独特的成膜和传热能力，分析了纳米生物润滑剂优异的磨削性能。结果表明，纳米生物润滑剂优异的传热和极压成膜性能显著改善了磨削区的极端摩擦条件，相比于传统微量润滑，表面粗糙度值（Ra）可降低约10%～22.4%。进一步地，阐明了多场赋能调控策略下，磨削区纳米生物润滑剂浸润与热传递增效机制。最后，针对纳米生物润滑剂的工程和科学瓶颈提出了展望，为纳米生物润滑剂的工业应用和科学研究提供理论指导和技术支持。     

非晶态Ni-P合金与纳米A12O3微粒复合镀层的制备

利用化学镀技术，制备了非晶态Ni—P合金基纳米A12O3复合镀层，研究了纳米A12O3微粒的加入量、加入方式以及搅拌方式等对复合镀层组织和形貌的影响。结果表明，纳米A12O3在加入到镀液中以前，应先选用适当的表面活性剂和分散介质制成单分散添加液，然后再加到镀槽中才可保证纳米粒子在镀层中的均匀弥散分布，在超声振动搅拌方式下，镀液中只需加入1g／L纳米A12O3，即可得到颗粒细小、分散均匀的非晶态Ni—P合金基纳米A12O3的复合镀层。     

同轴静电雾化切削雾化特性与加工性能研究

通过同轴静电雾化切削雾化、荷电性能及铣削铝合金试验,研究了电压和内外流体类型对雾化形态、雾化电流与稳定性、切削力的影响。结果表明,在适用于切削的稳定锥射流模式下增大喷嘴电压,雾化电流增加、稳定性降低。内外流体中纳米颗粒的加入都会增大雾化电流,降低雾化稳定性。外流体中加入纳米颗粒切削力显著降低,内流体中加入纳米颗粒切削力有所增大。内流体为去离子水,外流体为蓖麻油基纳米流体时获得最低的切削力,为同轴静电雾化切削的优化内外流体组合。     

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).     

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.     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。