金属纤维多孔材料的吸声性能

采用松装、压制、定位3种烧结方式制备了厚度为1~30 mm的不锈钢纤维多孔材料,采用丹麦BK公司的双传声器阻抗管测试吸声系数,系统研究了孔隙度和丝径对吸声性能的影响规律。结果表明:在不同厚度条件下,孔隙度有着不同的最佳范围值,如1~3 mm时,孔隙度在80%~85%的范围内,5 mm时,孔隙度在85%~90%的范围内,10~15 mm时,孔隙度在90%~94%范围内全频吸声性能较好,随着厚度的增加,这个最佳范围值随之增大;在厚度≤mm时,材料的丝径越细,全频吸声性能越好;当厚度在3~20 mm的范围内时,随着厚度的增加,粗丝径样品的吸声性能逐渐变好,其吸声峰值向低频移动,并且保持着高频处较好的吸声性能;当厚度220 mm时,材料的丝径越粗,全频吸声性能越好。     

超薄金属纤维复合膜材料的低频吸声性能

本文针对限域空间（≤5mm）噪声防护对超薄吸声结构的重大需求,以不锈钢纤维毡为原料,利用低温烧结技术制备了由不锈钢纤维多孔材料和金属薄膜组成的复合膜材料。利用B&K声学测试平台对复合膜材料进行频率范围在50~1000Hz之间吸声系数的测试,分析了结构参数对复合膜材料吸声性能的影响规律。结果表明,通过分别研究金属纤维多孔材料的孔结构（孔径、丝径、烧结结点）及金属薄膜的层数对复合膜材料吸声性能的影响规律,发现在频率为50~1000Hz的范围内,超薄复合膜材料的最优结构为金属纤维多孔材料按照细丝径、小孔面向声源,粗丝径、大孔在后的顺序排列,材料内部复合铜箔可有效提高材料在低频处的吸声性能。     

孔结构对不锈钢纤维多孔材料吸声性能的影响

本文设计两种不锈钢纤维多孔材料的铺制方法：平行铺制和直立铺制,通过控制铺制方法、长径比和烧结工艺得到具有不同孔结构的不锈钢纤维多孔材料,对具有不同孔结构的不锈钢纤维多孔材料的吸声性能进行分析,结果表明,长径比为5000的不锈钢纤维多孔材料的性价比最高;当材料厚度≤15mm时,平行铺制的纤维多孔材料较直立铺制的吸声性能好;当材料厚度＞15mm时,铺制方法的影响不显著;烧结结点数量的多少对不锈钢纤维多孔材料吸声性能贡献不大。     

Sound Absorption Characteristics and Structure Optimiza- tion of Porous Metal Fibrous Materials

以金属纤维多孔材料为研究对象（厚度≤3 mm）,以在狭小空间内用于吸声减振为背景,针对材料的制备工艺、结构参数等因素对其进行结构优化。结果表明,烧结温度较低、无烧结结点形成的结构,其吸声性能较好;而且在不同频率范围内,平均孔径和丝径可以通过最优搭配得到性能较好的吸声材料。通过结构优化设计,在烧结温度为850 ℃,当频率范围为50~6400 Hz时,丝径为Φ12 μm,平均孔径分别为10、30、40 μm的样品吸声性能较好。     

金属纤维多孔材料的吸声性能及结构优化（英文）

以金属纤维多孔材料为研究对象(厚度≤3 mm),以在狭小空间内用于吸声减振为背景,针对材料的制备工艺、结构参数等因素对其进行结构优化。结果表明,烧结温度较低、无烧结结点形成的结构,其吸声性能较好;而且在不同频率范围内,平均孔径和丝径可以通过最优搭配得到性能较好的吸声材料。通过结构优化设计,在烧结温度为850℃,当频率范围为50~6400 Hz时,丝径为Φ12μm,平均孔径分别为10、30、40μm的样品吸声性能较好。     

纤维多孔材料梯度结构的吸声性能研究

为了提高纤维多孔材料的低频吸声性能,并解决材料在高频段吸声性能的起伏问题,将2～3层不同孔隙性能的不锈钢纤维材料以不同的方式组合成梯度结构,研究了纤维多孔材料梯度结构的吸声性能.结果表明:梯度多孔吸声结构可有效改善低频吸声性能.不同孔隙度的排布方式对梯度结构的吸声性能有显著影响.按照孔隙度从高到低排布有利于吸声性能的提高.在此前提下,孔隙度越高、厚度越大,梯度结构的吸声性能越好.     

金属纤维多孔材料吸声性能研究现状

简要描述了金属纤维多孔材料的吸声原理及其应用领域,重点阐述了材料厚度、材料结构、金属纤维直径、孔隙度等因素对其吸声性能的影响规律。指出要深入系统研究各因素对吸声性能影响程度的优先次序,为制备具有良好吸声性能的金属纤维多孔材料提供理论支持和技术指导。     

不锈钢纤维多孔材料的吸声性能

采用不锈钢纤维为原料制备不同孔隙性能的纤维多孔材料，采用驻波管法检测该纤维多孔材料的空气声吸收系数，研究材料的孔隙度、纤维直径以及材料厚度等参数对吸声性能的影响，同时研究在材料背后设置空气层以及空气层厚度对材料吸声性能的影响关系。结果表明：实验采用的不锈钢纤维多孔材料具有较好的吸声性能，材料的孔隙度越高、厚度越大、纤维越细，材料的吸声性能越好，在材料背后设置空气层可显著改善其低频吸声性能，材料背后的空气层厚度越大，材料的低频吸声性能越好。     

烧结FeCrAl纤维多孔材料的吸声特性

采用Φ20 μm FeCrAl纤维制备纤维多孔材料,孔隙度大于85%.在常声压与高声压条件下分别对烧结FeCrAl纤维多孔材料进行吸声性能检测.结果表明,在常声压下,材料的吸声特性随孔隙度的增加而提高,但是对于高频的吸收,孔隙度过高或过低都不利于吸收.厚度越大,材料的吸声性能越好.增加空腔可以提高材料在低频的吸声性能;在高声压条件下(100～140 dB),该材料的吸声特性不随声压级的变化而变化,各参数对吸声性能的影响规律与在常声压条件下的规律一致.频率在2.5～6.4 kHz之间,声压级为120 dB条件下,孔隙度为94%、20 mm厚的FeCrAl纤维多孔材料吸声系数达到90%.     

Effect of Pore Structure on Performance of Porous Metal Fiber Materials

孔结构是影响金属纤维多孔材料各项性能的关键因素之一,为此研究了孔结构对其性能的影响规律。采用气流铺毡法和烧结技术制备了FeCrAl纤维多孔材料,利用SEM观察其微观组织,同时测试了其拉伸强度、透气性和吸声系数（声强为 90~140 dB,频率为1000~3000 Hz）。利用自主研发的分形软件计算了孔结构的分形维数。另外,研究了孔结构对多孔材料拉伸强度、吸声系数和透气性的影响规律,建立了拉伸强度、透气性与分形维数之间的本构关系。研究表明,随着分形维数的增加,抗拉伸强度呈线性下降,而透气性显著增大;在相同的声强和频率下,吸声系数随着分形维数的增加而逐渐降低     

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。