粉体粒度对HA/BG生物活性涂层组织结构的影响

采用亚音速火焰喷涂方法及涂层处理技术,以Ti6Al4V为基体喷涂不同粒度粉体,制备HA/BG生物活性涂层,并引入Ti/G过渡层缓解应力.涂层经700℃晶化处理.结果表明,粉体粒度决定了HA/BG涂层的组织结构.细小粉体可获得疏松、多孔结构的涂层,此种结构有利于涂层材料与骨组织之间结合.涂层经过700℃晶化处理后,主相为...     

亚音速火焰喷涂HA/BG仿生生物涂层

为提高HA涂层结合强度,避免涂层在使用过程中开裂及溶解脱落等问题,采用亚音速火焰喷涂方法及涂层晶化处理,以Ti6Al4V为基体,引入热膨胀系数与基体相近的Ti/G过渡层缓解应力,工作层以HA为主,辅以生物活性玻璃(BG),喷涂制备HA/BG仿生生物涂层.通过调整BG含量,观测涂层形貌、相组成及结构的变化,进而分析HA/BG仿生生物涂层作为骨组织替代材料的适用性.结果表明:亚音速火焰喷涂HA/BG仿生生物涂层具有典型的热喷涂涂层形貌特征,与基体结合较好,没有明显的开裂脱落现象,涂层经700℃晶化处理后析出纳米和微米级HA,可增加与宿主骨组织接触面积,加快其反应,增加生物活性.添加BG后,涂层中有新相Na2Ca(PO4)F析出;当改变BG含量后,可改变HA、Na2 Ca (PO4)F晶相的含量,进而来调控涂层的溶解性和稳定性.     

热处理对钛-生物玻璃涂层结合强度的影响

为了提高涂层与钛合金基体的结合强度,采用高速火焰喷涂方法,在Ti6Al4V钛合金基体表面喷涂不同比例的钛-生物玻璃复合涂层,喷涂后试样以5℃/min加热至700℃保温1h后随炉冷却。结果表明:高速火焰喷涂方法制备以钛为主粉,添加不同含量底釉生物玻璃(G),获得的涂层热处理前后结合强度范围在38～57MPa之间。涂层结合强度受喷涂粉体G添加量和热处理的影响。随着G添加量增加,结合强度升高,涂层经热处理后,结合强度略有下降。热处理释放了喷涂时产生的应力,使纯钛涂层裂纹加宽。而G的加入,与钛相互作用,发生浸润、扩散,涂层有再结晶和新相沿裂纹析出,起到修复裂纹的作用。     

铜基体上超音速火焰喷涂镍基涂层残余应力分析

采用X射线应力分析技术和曲率法测试了在铜基体上喷制不同成分、厚度的镍基涂层以及改变基体厚度喷制的涂层的残余应力。结果表明,超音速火焰喷涂的镍基涂层残余应力均为压应力,涂层成分、厚度的变化对残余应力均有明显的影响,添加一定量的WC、控制涂层和基体厚度,可获得较大的残余压应力。     

高速火焰电弧复合喷涂枪制备3Cr13涂层的性能

高速火焰电弧(HVAF-ARC)复合喷涂枪是高速火焰喷涂枪和电弧喷涂枪的结合体,利用产生的高速燃气来雾化加速电弧喷涂过程中产生的熔融粒子,提高了喷涂粒子的飞行速度,降低了粒子的氧化,可高效制备优质的涂层。文中利用自主开发的新型高速火焰电弧复合喷涂枪和普通高速电弧喷涂枪,分别在钢基体上制备了3Cr13涂层,通过对涂层的性能检测发现,复合喷涂枪所制备涂层的氧元素含量和孔隙率都比普通高速电弧喷涂枪制备的涂层低,分别降低了33%和49%,硬度提高了12%,复合喷涂枪制备涂层的性能得到较大的提高。     

ZrO2热障涂层残余应力分析

用扫描电子显微镜(SEM)观察了等离子喷涂ZrO2涂层的显微结构,并用X射线衍射法(XRD)测试了ZrO2涂层相的组成和残余应力.同时测试了激光冲击处理和激光热处理后的ZrO2涂层残余应力分布,分析了热障涂层残余应力形成机理.结果表明,等离子喷涂ZrO2涂层表面残余应力均为拉应力,其均值为179.2MPa,经激光表面处理后的ZrO2涂层残余应力均表现为压应力;热应力对涂层残余应力贡献最大,当热应力超过涂层结合强度时,涂层脱落,通过控制涂层残余应力可以提高涂层界面结合强度.     

铜基体上超音速火焰喷涂镍基涂层残余应力分析

采用X射线应力分析技术和曲率法测试了在铜基体上喷制不同成分、厚度的镍基涂层以及改变基体厚度喷制的涂层的残余应力。结果表明，超音速火焰喷涂的镍基涂层残余应力均为压应力，涂层成分、厚度的变化对残余应力均有明显的影响，添加一定量的WC、控制涂层和基体厚度，可获得较大的残余压应力。     

表面工程应用实例 [例12]超音速火焰喷涂用于冷轧张力辊的复合制造与再制造

超音速火焰喷涂(简称HVOF)是利用可燃气体在氧气助燃下释放的化学能为热源,燃气在特殊结构的喷涂枪中形成超音速焰流使喷涂粉末以熔融状态高速撞击到工件表面制备出喷涂层.超音速火焰喷涂的特点:具有高的喷涂粒子速度和相对较低的温度,特别适合于喷涂WC等金属陶瓷材料;喷涂层的压应力结构有利于制备较厚的涂层;喷涂效率高,燃气价格较低,经济性好.     

[例12]超音速火焰喷涂用于冷轧张力辊的复合制造与再制造

超音速火焰喷涂(简称HVOF)是利用可燃气体在氧气助燃下释放的化学能为热源,燃气在特殊结构的喷涂枪中形成超音速焰流使喷涂粉末以熔融状态高速撞击到工件表面制备出喷涂层.超音速火焰喷涂的特点:具有高的喷涂粒子速度和相对较低的温度,特别适合于喷涂WC等金属陶瓷材料;喷涂层的压应力结构有利于制备较厚的涂层;喷涂效率高,燃气价格较低,经济性好.     

纳米掺杂Al2O3基等离子喷涂涂层残余应力分析

利用逐层剥离X射线衍射法,测定了纳米粒子掺杂对Al2O3 13%TiO2(AT13)等离子喷涂涂层残余应力的影响.结果证明AT13等离子喷涂涂层残余应力分布为:陶瓷涂层部分为压应力;Al/Ni过渡层由陶瓷涂层到钢基体,由压应力过渡到拉应力;在距钢基体0.05mm处现拉应力峰值.随着纳米掺杂量的增大,陶瓷涂层及Ni/Al过渡层残余应力绝对值降低,这对改善陶瓷涂层性质是十分有益的.     

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.     

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。