自蔓延高温合成Cf/TiC-TiB2复合材料的力学性能研究

为提高TiC-TiB2复合材料的强度和韧性以拓宽其应用,用自蔓延高温合成结合准热等静压(SHS/PHIP)的方法制备了碳纤维质量分数分别为0%,1%,3%,5%,7%的Cf/TiC-TiB2复合材料.通过实验测定,随碳纤维含量的增加,Cf/TiC-TiB2复合材料的弯曲强度和断裂韧性都呈现先增加后降低的趋势.当碳纤维含量达到3%时,强度和韧性分别为406.12 MPa和6.26 MPa.m1/2,均高于纯TiC-TiB2陶瓷.纤维的断裂、桥连和裂纹的偏转是复合材料的主要增韧机制.     

TiB2含量对TiB2/Cu复合材料性能的影响

研究了TiB2含量对原位生成TiB2／Cu复合材料性能的影响。结果表明：TiB2／Cu复合材料的硬度、强度随TiB2含量的增加有所提高，但强度在TiB2的含量超过2．0％后有所下降，导电率随TiB2含量的增加有所下降，软化温度基本保持在900℃左右。     

增强相含量对原位(TiB+TiC)增强钛基复合材料组织与性能的影响

采用放电等离子烧结法制备了(TiC+TiB)/TC4复合材料，并研究了TiC和TiB增强相含量对钛基复合材料物相组成、微观结构和力学性能的影响。采用SPS温度为1 100℃原位合成制备出(TiC+TiB)/TC4复合材料，TiCp和TiBw呈准连续的网状结构分布在晶界处。样品按照TiC∶TiB为1∶1的比例来制备出增强相体积分数为x%(x=0、1、2.5、5、7.5)增强钛基复合材料。在增强相的体积分数为2.5%时复合材料的屈服强度、抗压强度最高，分别为1 264和1 803 MPa,工程应变由基体合金的30%增加至39.4%。     

在位生成TiB2／Al—Si—Mg复合材料的组织与性能

结合LSM法和MCR法原位反应生成TiB2粒子增强Al-Si-Mg复合材料。研究发现,原位生成TiB2粒子呈等轴状且尺寸＜1um,大都均匀分布在共晶组织中,与共晶Si交织在一起,在α（Al)中只有少量的TiB2粒子。原位TiB2粒子可明显强化Al-Si-Mg复合材料,且随着TiB2粒子数量的增加,强化效果也随之提高,而且延伸率也略有升高,如6％TiB2/Zl104复合材料室温拉伸强度可达296MPa,延伸率为5．5％,热处理（T6)可将共晶Si由原先的连续棒状变为孤立的颗粒状,大幅度提高材料抗拉强度,使6％TiB2/Zl104复合材料室温拉伸强度达386MPa,而材料仍属于韧性材料。     

TiB2—TiC和TiB2—SiC陶瓷复合材料的活化烧结

TiC、TiB2和SiC都具有许多非常重要的性能，其中包括强耐磨性、高熔点、高硬度和良好的化学稳定性．加入第二相能够提高碳化物陶瓷的强度和韧性．往SiC基体内添加TiB2或者TiC粒子就能够大大提高SiC制品的断裂韧性，SiC含量高的材料用于生产耐磨和耐蚀制品，而TiC和TiB2含量高的材料则在电子技术方面具有广阔的前景．俄罗斯莫斯科罗蒙诺夫精微化学工艺研究所（MNTXY）的彼得洛夫和．列文斯基指出，目前这些复合材料尚未得到广泛的工业普及，原因是由担本混合物（热压坯料）制取致富产品的成本高和韧性低．在烧结这些材料时，扩散一…     

共沉淀法原位合成无压烧结TiB2／B4C陶瓷复合材料

以TiCl4溶液和B4C粉末为主要原料，采用共沉淀、原位合成无压烧结技术制备了TiB2／B4C陶瓷复合材料。研究了原料配比、烧结温度对TiB2／B4C陶瓷复合材料的烧结性能、显微组织和力学性能的影响。通过X射线衍射、金相显微镜、扫描电镜等分析手段，分析了TiB2／B4C陶瓷复合材料的物相组成、显微组织和断裂特征。研究结果表明：当成分质量配比TiB2：B4C为40：60时，材料最大相对密度为98．5％T．D；在最佳成分配比下，随着烧结温度的升高，原位合成制备的TiB2／B4C陶瓷复合材料的密度、硬度、抗弯强度均为先升高后降低，材料的最佳烧结工艺为2050℃，1h。在最佳烧结工艺下，TiB2/B4C陶瓷复合材料的密度、硬度、抗弯强度和断裂韧性达到最佳值分别为3．17g／cm^3，31．5GPa，381MPa和5．1MPa．m^1/2.     

原位TiB2颗粒增强铝基复合材料及其力学性能

对原位反应合成TiB2／A356铝基复合材料微观组织和力学拉伸性能进行了研究。结果表明，原位反应生成的颗粒增强相在复合材料基体中分布均匀，基体与颗粒间的界面洁净。复合材料强度随着颗粒含量的增加显著提高，与基体合金相比，TiB2质量分数为8％的TiB2／A356复合材料强度和弹性模量的提高幅度约为28％，TiB2质量分数为16％的TiB2／A356复合材料强度和弹性模量的提高幅度约为35％。复合材料的断裂主要是由于基体与颗粒界面脱粘，在拉伸应力作用下由此萌生微裂纹并扩展，导致界面处的基体撕裂，从而降低复合材料塑性。     

原位合成TiB2/ZL109复合材料的力学性能

通过原位合成法成功制备了亚微米级TiB2颗粒增强ZL109复合材料，测量了不同颗粒含量复合材料的弹性模量和25～400℃的抗拉强度（UTS）。结果表明，复合材料的弹性模量随颗粒含量提高而提高，颗粒含量15％（质量分数，下同）时，复合材料的弹性模量比基体合金提高了32％；抗拉强度也明显高于基体合金，10％TiB2／ZL109复合材料在260℃时的强度比基体合金提高了105MPa。     

铝热快速凝固工艺合成高强TiC/FeNiCr复合材料

采用铝热快速凝固工艺制备了FeNiCr合金及TiC／FeNiCr复合材料，利用光学显微镜、扫描电镜、X射线衍射等手段研究了该复合材料的显微组织和相结构，测量了复合材料的压缩强度。结果表明，TiC／FeNiCr复合材料由TiC陶瓷增强相和α-Fe合金基体组成。TiC／FeNiCr复合材料组织细小，TiC呈多边形均匀分布在合金基体中，晶粒尺寸约为2～3μm。TiC对FeNiCr基体具有很好的晶粒细化及强化作用，TiC／FeNiCr的压缩断裂强度及形变率分别为2760MPa及25％，远大于FeNiCr合金及部分Fe基非晶材料。     

粉末冶金TC4-B4C原位反应制备TiC+TiB增强TC4基复合材料的显微组织和力学性能

以TC4和B₄C粉末为原料，通过放电等离子烧结法(SPS)并结合热挤压制备不同含量TiB和TiC增强TC4基复合材料，研究以TC4-B₄C为原位反应体系生成不同含量TiB和TiC对TMCs的微观组织和力学性能的影响规律及其高温力学性能。结果表明：原位生成的TiC和TiB与基体结合牢固，TiC呈类球形颗粒状，TiB呈晶须状；增强相在基体中呈现出沿一次颗粒边界分布的三维网络状形貌；与未增强TC4合金相比较，复合材料基体晶粒显著细化，并存在较高的位错密度，TC4基复合材料的室温和高温性能得到显著提升；在室温拉伸下，当B₄C的含量(质量分数)为0.5%时，基体的连通性较好，表现出较高的强度(抗拉强度1246 MPa)和较好的伸长率(12.4%)；在400℃下进行拉伸时，当B₄C的含量为1.64%时，TC4基复合材料的抗拉强度和伸长率分别为1112 MPa和6.9%。     

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。