Pt+Hf改性的γ-Ni+γ′-Ni3Al涂层结构及其抗氧化性能研究

通过包埋Al-Hf共渗在高温合金DZ417G表面制备出Pt+Hf共同改性的γ-Ni+γ′-Ni3Al涂层。Al-Hf共渗过程中,Hf含量不同,涂层表面形成的相结构也不同。当渗剂中Hf含量为2%时(质量分数,下同),涂层呈γ-Ni+γ′-Ni3Al结构;渗剂中Hf含量为6%时,涂层相结构为?-NiAl+Al16Hf6Ni7;而当Hf含量达到12%时,涂层相结构为Al16Hf6Ni7。随着后续热处理的进行,β-NiAl+Al16Hf6Ni7涂层的相结构转变为γ-Ni+γ′-Ni3Al;Al16Hf6Ni7涂层转变为γ-Ni+γ′-Ni3Al+Al3HfNi12结构。1100℃的等温氧化实验表明,经过10 h氧化,高温合金基体表面已经出现了脱落;而渗剂中Hf含量为2%时形成的Pt+Hf改性的γ-Ni+γ′-Ni3Al涂层经过30 h氧化后,其表面依然完整。与单纯的Pt改性的γ-Ni+γ′-Ni3Al涂层相比,Pt+Hf共同改性的γ-Ni+γ′-Ni3Al涂层由于适量活性元素Hf的加入,其抗氧化性能得到了提高。     

空心阴极电弧镀NiCrAlY涂层的抗氧化性能

采用空心阴极电弧离子镀技术制备NiCrAlY涂层,研究涂层的高温抗氧化性能。结果表明涂层组织致密,与合金结合状态良好。电弧离子镀NiCrAlY涂层在1 100℃恒温氧化100h后增重只有2.22mg/cm2,在100次循环氧化后仍没有失重现象,其抗恒温氧化和抗循环氧化性能远优于成分相近的超音速火焰喷涂、爆炸喷涂和大气等离子喷涂的NiCrAlY涂层。电弧离子镀NiCrAlY涂层在恒温氧化和循环氧化过程中表面均形成了连续致密、粘附性的氧化铝保护膜。氧化膜没有翘起和剥落现象,涂层组织在氧化后仍然完整致密。热喷涂NiCrAlY涂层在上述氧化过程中则生成了保护性较差的Ni、Cr和Al混合氧化物,并发生了氧化膜剥落,同时有严重的内氧化现象。     

真空热处理对镍基单晶高温合金溅射NiCrAlY涂层抗氧化性能的影响

用磁控溅射法在镍基单晶高温合金基体上沉积NiCrAlY涂层，研究了真空热处理对涂层组织结构及抗氧化性能的影响。结果表明，溅射NiCrAlY涂层主要由γ－Ni和β－NiAl两相组成，元素分布均匀；经真空热处理后，涂层主要由γ‘－Ni3Al、β－NiAl相和极少量的α－Al2O3相组成，元素分布变得不均匀，最外层富Al贫Cr。真空热处理可使溅射NiCrAlY涂层表面较早生成保护性能良好的α－Al2O3.1000℃氧化200h，溅射涂层氧化膜有较大部分已经剥落，但真空热处理涂层的氧化膜仍较好地粘附在涂层基体上。真空热处理使溅射NiCrAlY涂层表面生成的氧化膜粘附性更好，提高了溅射NiCrAlY涂层的抗氧化性能。     

CMSX-4合金单渗Al和Pt-Al涂层的高温氧化

研究了CMSX-4 Ni基高温合金的单渗Al和Pt改性渗Al涂层在1100℃空气中的氧化行为.Pt的存在,通过阻止合金元素穿过Al2O3膜向外扩散,改善Al2O3膜与基体的结合力,抑制γ-Ni3Al相的形成,推迟涂层的高温退化,同时讨论Pt的作用机制.     

Pt改性镍基高温合金铝化物涂层研究进展

综述了镍基高温合金上抗高温氧化的Pt改性β-(Ni,Pt)Al涂层和γ-γ′型涂层,重点介绍了Pt改性铝化物涂层制备工艺,不同工艺条件下涂层的微观结构,Pt增强铝化物涂层抗氧化性能的作用机理,Al对涂层高温氧化性能的影响,并从元素互扩散、相变、表面起伏等方面描述了涂层退化过程,最后对Pt改性铝化物涂层发展进行展望。     

(MCrAlY+AISiY)复合涂层的高温氧化行为

采用电弧离子镀技术在镍基高温合金K465上制备了(MCrAlY+AlSiY)复合涂层,分析了复合涂层的组织及结构,对比研究了NiCoCrAlYSiB单一涂层及(NiCoCrAlYSiB+AlSiY)复合涂层分别在1000及1100℃时的恒温氧化行为和从1000℃到室温的循环氧化行为.结果表明:退火后复合涂层外层主要由β-(Ni,Co)Al相及少量σ-NiCoCr和CraSi相组成,内层主要是富Cr相及少量β-(Ni,Co)Al相.氧化过程中由于Al的消耗,单一涂层表面生成了尖晶石和NiO,而复合涂层中的β-(Ni,Co)Al相退化成γ/γ'相,提供Al源支持表面Al2O3膜的形成和修复,从而提高了抗高温氧化性能.     

(Ni,Pd)Al涂层的抗高温氧化性能

采用低压固体粉末包埋渗铝方法在M38镍基高温合金上制备钯改性铝化物涂层，利用热重分析(TGA)、扫描电镜(SEM)、X射线衍射(XRD)等方法，研究其l100℃的高温氧化行为．结果表明，(Ni，Pd)Al涂层的恒温氧化动力学近似符合抛物线氧化规律．与NiAl涂层相比，(Ni，Pd)Al涂层具有更优良的抗高温氧化性能，退化过程与NiAl涂层类似．添加改性元素Pd有利于稳定β相，延缓涂层的退化，有益于提高铝化物涂层的抗高温氧化性能．     

梯度NiCrAlY涂层的1000和1100℃氧化行为研究

采用电弧离子镀技术及后续热处理工艺在镍基高温合金上制备了均匀NiCrAlY涂层和梯度NiCrAlY涂层,分析了2种涂层的组织结构,对比研究了2种涂层静态空气下1000和1100℃恒温氧化行为以及1100℃的循环氧化行为.结果表明:均匀NiCrAlY涂层由γ′/γ相和少量β-NiAl相、α-Cr相组成,成分分布均匀;梯度NiCrAlY涂层具有外层富Al和内层富Cr的结构,其中外层由β-NiAl相和少量γ′/γ相、α-Cr相组成.一方面,梯度涂层的初始Al含量较高;另一方面,氧化过程中其富Cr区两侧出现了对富Al区的Al向基体扩散起阻碍作用的Cr(W)析出带.这两方面使梯度涂层长时间维持更多的Al存储相,提升了氧化膜的迅速生成及再生成能力,从而使涂层具有较好的抗氧化性能.     

NiCrAlY涂层对Ni基高温合金K17抗氧化性能的影响

采用电弧离子镀技术在铸造Ni基高温合金K17上沉积NiCrA1Y涂层，测定了K17合金和NiCrAlY涂层在900℃-1100℃的氧化动力学曲线。实验结果表明：K17合金和NiCrAlY涂层在不同温度静态空气中氧化动力学曲线基本符合抛物线规律。900℃和1000℃时，K17合金上沉积NiCrAlY涂层后，明显改善了合金的抗氧化性。1100℃时，涂层的保护作用不如900℃和1000℃，900℃氧化时，NiCrAlY涂层氧化膜由α-Al2O3和Cr2O3的组成；1000℃氧化时，氧化初期，NiO,Cr2O3和Al2O3 3种氧化物同时生成。随着氧化的进行，不仅氧化膜增厚，而且发生较复杂的反应，氧化膜的相组成发生变化。随着氧化温度升高，涂层和基体之间元素扩散加剧，Ti从基体扩散到涂层表面形成氧化物是导致涂层抗氧化降低的原因。氧化膜从涂层上剥落下来，也导致了涂层抗氧化能力降低。     

NiCrAIY涂层对Ni基高温合金K17抗氧化性能的影响

采用电弧离子镀技术在铸造Ni基高温合金K17上沉积NiCrAlY涂层,测定了K17合金和NiCrAlY涂层在900℃～1100℃的氧化动力学曲线.实验结果表明:K17合金和NiCrAlY涂层在不同温度静态空气中氧化动力学曲线基本符合抛物线规律.900℃和1000℃时,K17合金上沉积NiCrAlY涂层后,明显改善了合金的抗氧化性.1100℃时,涂层的保护作用不如900℃和1000℃.900℃氧化时,NiCrAlY涂层氧化膜由α-A12O3和Cr2O3组成;1000℃氧化时,氧化初期,NiO、Cr2O3和A12O3 3种氧化物同时生成.随着氧化的进行,不仅氧化膜增厚,而且发生较复杂的反应,氧化膜的相组成发生变化.随着氧化温度升高,涂层和基体之间元素扩散加剧,Ti从基体扩散到涂层表面形成氧化物是导致涂层抗氧化性降低的原因之一.氧化膜从涂层上剥落下来,也导致了涂层抗氧化能力降低.     

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).     

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。