渗铝-真空预氧化制备FeAl/Al2O3防氚渗透涂层性能

在核级316L不锈钢基体上,采用固体埋层渗铝和真空预氧化工艺制备FeAl/Al2O3防氚渗透自修复涂层,研究了这种渗铝氧化涂层的表面形貌、化学成分、相组成以及涂层表面纳米级氧化膜的厚度的SEM/EDS、XRD、XPS、AES、RBS等测试分析与表征方法.结果表明:该复合涂层由约20μm厚的Fe-Al扩散层以及约200nm厚的表面Al2O3氧化层组成;Fe-Al扩散层的主要相组成为FeAl及少量Fe3Al、NiAl、α-Fe相,微观观察表明由外渗铝层、过渡层、内扩散层构成.     

HR-2不锈钢室温熔盐镀铝

为在不锈钢表面制备铝化物阻氚渗透层奠定基础,采用AlCl3-MEIC（氯化1-甲基3-乙基咪唑）室温熔盐在HR-2不锈钢表面进行镀铝实验,主要研究镀前处理方式,电流密度对镀层的形貌、结合力、纯度的影响。结果表明,采用AlCl3-MEIC室温熔盐体系在HR-2不锈钢上镀铝是可行的。传统的酸洗镀前处理能得到质量较高的镀层,但界面结合不好;电化学清洗镀前处理后可制得结合良好的高质量镀层。纯白色铝镀层表面光滑、均匀、致密,呈现有一定棱角的球形颗粒状生长特性。镀层颗粒尺寸随电流密度的增加而增大。较优的电流密度范围为10~20 mA?cm-2,电镀时间至少40 min。     

T92钢表面铝化物涂层的组织演化

在高温下长时间暴露,钢材表面的渗铝层与母材之间容易发生元素互扩散,对母材组织产生影响,影响母材的力学性能。为研究超超临界机组用T92钢表面铝化物涂层的抗蒸汽氧化性能及组织演化特性,采用低温粉末包埋渗铝法在T92钢锅炉管内壁制备铝化物涂层,并在650℃饱和蒸汽环境中进行热暴露试验,结合扫描电镜（SEM）、透射电镜（TEM）观察及X射线衍射分析,研究铝化物涂层的氧化行为以及T92基体与铝化物涂层之间的扩散退化行为。研究结果表明：低温粉末包埋渗铝可在T92锅炉管内壁制备厚度约30.4μm的双层结构铝化物涂层,各层结构连续均匀且组织稳定,与母材呈冶金结合。在650℃、3 000 h饱和蒸汽氧化过程中,涂层表面生长厚度约0.3μm的α-Al2O3氧化膜。650℃长时热暴露过程中,Fe-Al金属间化合物始终是涂层的主要物相,但涂层由FeAl相向FeAl2相退化。铝化物涂层经长时间热暴露后组织退化,但仍具有优异的抗氧化性能,能够对T92钢提供很好的保护。     

P11O钢表面韧性FeAl渗层的低温制备

通过在摩尔比为2∶1的AlCl3-EMIC(氯化1-甲基3-乙基咪唑)室温离子液体中电沉积铝镀层加低温热处理的方法,在P110钢表面进行低温渗铝.用金相显微镜(OM)、扫描电子显微镜(SEM)、能量散射X射线谱仪(EDS)和X射线衍射(XRD)研究了渗层的组织结构.结果表明:为保证P110钢基体的硬度,热处理温度应低于620℃,而渗铝速度在高于590℃时较快.6 μm铝镀层试样经620℃×24 h热处理,可以得到8μm由韧性FeAl相组成的渗层.     

FeAl/Al_2O_3复合阻氚涂层制备技术的研究进展

FeAl/Al_2O_3复合膜层是聚变堆氚增殖包层及辅助涉氚系统结构材料首选的阻氚涂层。其制备过程通常需要铝化和氧化2个步骤,铝化是Al原子与基体Fe原子通过相互扩散在基体表面形成铁铝固溶体(Fe,Al)或Fe-Al金属间化合物过渡层;氧化是使铝化涂层表面选择性氧化形成Al_2O_3膜。该阻氚涂层的制备可采用物理气相沉积(PVD)、化学气相沉积(CVD)、热浸铝化(HDA)、包埋渗铝(PC)、等离子体喷涂(PS)和电化学沉积(ECD)等技术。相对而言,CVD、HDA和PC等3种技术有较好的应用前景,有望成为聚变堆中FeAl/Al_2O_3阻氚涂层工程化制备的候选技术而ECD技术因其制备过程容易控制、涂层性能稳定、可涂镀复杂结构件等特点在FeAl/Al_2O_3阻氚涂层制备方面颇具吸引力。     

HR-2不锈钢表面渗Al涂层的制备

为避免制备温度过高引起基体性能退化,采用了室温熔盐电镀与热处理复合技术在HR-2不锈钢卜进行了渗Al涂层制备研究,并对涂层的形貌、结构和成分进行了表征.结果表明,利用该技术制备渗Al涂层是可行的;经500℃和700℃两种温度下热处理,成功制得成分渐变,冶金结合且无缝隙和裂纹的10-15 μm厚渗Al涂层.经700℃下2 h热处理后,渗Al涂层与基体无明显界面,依次由(Fe,Cr,Mn,Ni)2Al5,(Fe,Cr,Mn,Ni)Al和(Fe,Cr,Mn,Ni)3Al3层组成;与700℃热处理后不同,经500℃下10 h热处理后,渗Al涂层与基体间界面明显,由内外两层组成.     

CLAM钢表面铝化物涂层的制备与铅液相容性研究

目的探索铝化物涂层的制备工艺,研究其是否能有效抑制铅液对CLAM钢的腐蚀。方法用配制的渗剂对CLAM钢进行包埋渗铝,并通过随后的热扩散和原位氧化处理,在CLAM钢表面制备铝化物涂层,研究不同渗铝时间和热扩散时间对涂层厚度的影响。通过静态氧化试验和铅液腐蚀试验,分别评价铝化物涂层的抗氧化性能及其与铅液的相容性,采用XRD、SEM和EPMA分析涂层的相组成以及铅液腐蚀前后的微观形貌和元素分布。结果包埋渗铝+热扩散+原位氧化处理制备的铝化物涂层主要由约30μm的FeAl相层和约70μm的α-Fe(Al)固溶体层组成。在热处理过程中,由于Al和Fe的互扩散现象,涂层中的Fe-Al相依次经过了Fe₂Al₅、FeAl₂、FeAl、Fe₃Al和α-Fe(Al)的转变。在600℃空气中静态氧化120 h后,铝化物涂层试样氧化质量增量为0.028 mg/cm²,比CLAM钢的氧化质量增量降低了1个数量级,铝化物涂层使CLAM钢的氧化动力学曲线由直线规律转变为抛物线规律。经550℃铅液腐蚀600、1800 h后,铝化物涂层的腐蚀质量增量分别为0.058、0.077 mg/cm²,仅约为CLAM钢的1/120。CLAM钢表面产生了疏松多孔的铁氧化物层,而铝化物涂层没有发生明显的腐蚀,但是腐蚀1800 h后,随着表面铝含量的不断消耗,Al₂O₃层厚度逐渐减小。结论铝化物涂层具有良好的抗氧化性能及与铅液的相容性,能够有效抑制铅液对CLAM钢的腐蚀。     

渗铝氧化处理对CLAM钢组织和力学性能的影响

采用合适的渗铝氧化处理工艺在CLAM钢基体表面制备了铝化物涂层,然后利用XRD、EPMA、SEM、纳米压痕仪、室温拉伸试验机等手段研究了渗铝氧化处理前后组织和力学性能变化,尤其是涂层的相组成变化,进而详细分析了硬度变化和拉伸断口的断裂机制。结果表明,渗铝氧化处理后在CLAM钢表面形成了由约30.8 μm厚的FeAl相层和约70.7 μm厚的α-Fe(Al)固溶体层组成的铝化物涂层,最外层FeAl相的硬度最大为834.7 HV,由外向内硬度逐渐降低至315.1 HV,基体内部的硬度出现略微回升。CLAM钢在渗铝氧化前后的抗拉强度分别为581.38 MPa和555.83 MPa,断后伸长率分别为30%和28%,断裂模式由渗铝氧化前的韧性断裂变成准解理断裂。由于渗铝及氧化热处理导致的晶粒尺寸增大和第二相粒子聚集,CLAM钢在渗铝氧化后拉伸性能下降,同时在表面涂层处易产生裂纹源从而加速材料断裂。     

铁素体不锈钢室温熔盐镀铝层的热处理

以1Cr17铁素体不锈钢为基体,在摩尔比2∶1的酸性AlCl3-EMIC(1-甲基-3-乙基咪唑氯化物)室温熔盐中电沉积均匀致密的铝镀层,然后分别在300℃、650℃6、70℃下进行不同时间的热处理,用刻划撕扯法判断镀层的结合力,用SEM、EDS及XRD对热处理后的试样界面进行微观分析。结果表明,试样经热处理后,结合力有了很大提高,镀层与基体之间发生互扩散形成合金层,合金层由含Cr的Fe2Al5、FeAl、Fe3Al等相组成,且随着温度提高及热处理时间的增长,镀层由Fe2Al5相进一步转变成铁含量高、韧性高的FeAl、Fe3Al相。     

热扩散处理电弧离子镀铝涂层的结构及其抗氧化性能

为了提高抗氢钢的抗高温氧化能力,采用电弧离子镀在抗氢钢上沉积Al涂层,通过高温热扩散处理,制备得铝基复合涂层。试验了不同温度对铝基复合涂层性能的影响,采用X射线光电子能谱仪（XPS）、X射线能谱仪（EDS）、X射线衍射仪（XRD）和扫描电镜（SEM）等分别测试了涂层的成分、晶体结构及表面、剖面形貌,通过高温氧化试验测试了涂层的抗高温氧化性能。结果表明： 电弧离子镀Al涂层经热扩散处理后,剖面结构为分层分布,表层为Al2O3层,700 ℃处理后的厚度约0.7 μm,为非晶态;950 ℃处理后的厚度约为2.2 μm,为α相。内层为热扩散层,700 ℃形成成分含量不同的两层热扩散层,由FeNiAl5、FeAl3、Fe4Al13及Ni2Al3等多种富铝相组成;950 ℃形成热稳定相立方体的FeAl和NiAl相。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.