Cr涂层Zr-4合金包壳的高温空气氧化/扩散行为

目的 在Zr合金包壳表面制备Cr涂层,以提高Zr合金包壳在事故环境下的抗高温氧化性能。方法 采用多弧离子镀技术在Zr-4合金包壳上制备约17 μm的Cr涂层,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、能量色散光谱(EDS)和电子探针(EPMA)等方法,分析试样氧化前后的相组成、微观形貌和扩散行为,并评估试样在1 100、1 200、1 300 ℃空气环境中氧化后的高温氧化性能。结果 沉积态Cr涂层显微结构致密均匀,(110)面有很强的织构。Cr涂层在高温空气中氧化60 min后,保持了涂层结构完整性。氧化后的Cr涂层Zr合金系统均为多层结构,包括外部Cr2O3层、中间Cr涂层、内部Cr-Zr扩散层和Zr合金基体。在涂层/基体界面上形成了具有Laves相的金属间ZrCr2扩散层,ZrCr2层下方的区域出现了大量分散的沉淀相。在Cr-Zr中间层和Zr合金界面处的不对称原子扩散导致Kirkendall空位生成,空位的聚集和合并导致空穴的形核和生长。结论 Cr涂层表面形成了致密的Cr2O3层,提高了Zr-4合金的抗高温氧化性能。通过研究高温空气中Cr涂层Zr-4合金包壳材料的高温空气氧化/扩散行为,可为耐事故涂层的开发、制备和应用提供一定的理论指导和技术支持。     

锆合金表面Cr涂层的循环热冲击行为

为了研究锆合金表面 Cr 涂层的循环热冲击行为,使用自研的热冲击设备模拟循环热冲击环境,针对多弧离子镀技术制备的 Cr 涂层进行不同循环次数的热冲击试验。通过 X 射线衍射仪(XRD)和显微硬度计分别分析热冲击前后的物相变化和硬度变化,采用扫描电镜(SEM)和能谱仪(EDS)探究 Cr 涂层的表面破坏行为。循环热冲击过程中,Cr 涂层生成的氧化层有“自愈”效果,可以有效阻挡 O 进入锆合金基体,同时诱发 Cr-Zr 中间层的非均匀扩散。大量 Cr 元素的内部扩散会促使 α-Zr(O)的生成。热冲击生成的裂纹大量分布于外部氧化层、非均匀扩散的中间层以及 α-Zr(O)层。经过 N=24 次循环热冲击后,残余的 Cr 涂层仍然可以有效保护锆合金基体,避免 Zr 与大量 O 反应。通过将锆合金表面 Cr 涂层的循环热冲击行为分为三个阶段,进一步揭示了循环热冲击作用下锆合金 Cr 涂层的组织结构和抗热冲击性能的演变规律。     

电弧离子镀制备耐事故包壳材料厚Cr涂层及高温抗氧化性能

目的在Zr-4包壳材料表面制备具有耐事故高温性能的抗氧化厚Cr涂层,保护Zr基体,以防止与高温水蒸汽反应。方法采用自主研发的φ155 mm大弧源电弧离子镀技术在Zr-4合金表面制备约20μm的Cr涂层,通过X射线衍射仪(XRD)分析氧化前后的物相变化,通过扫描电子显微镜(SEM)和电子探针(EPMA)研究厚Cr涂层在不同温度下产生的多种缺陷,探究厚Cr涂层对Zr基体的防护机制。结果当涂层沉积速率3μm/h,制备的Cr涂层均匀致密,结合力优异,具有柱状晶结构,可经受至少15.8%的形变量,其抗塑性形变能力优异。沉积Cr层样品经过1000、1100、1200℃氧化,保温1h后快速冷却至室温,厚Cr涂层分化为Cr Ox层、Cr_2O_3层、残余Cr层和Cr-Zr扩散层。经受苛刻条件(1200℃/3600 s)测试,除保持连续性的氧化层外,在基体上仍残余良好结合的6.8μm Cr层。氧化层两次开裂阻止基体被进一步破坏。Cr-Zr扩散层是由Zr元素向Cr涂层方向渗透生长的。1200℃时,在基体近表面处产生的大尺寸隆起,是由于在近表面处韧性β-Zr(O)相转变为脆性α-Zr相,以及Cr偏聚贫Sn造成的。残余Cr层的柱状晶结构会形成Zr-O扩散通道,对涂层最后失效将起关键作用。结论 Zr合金包壳材料镀覆20μm的Cr涂层具有充分的耐事故能力,在严苛的事故条件测试下,各缺陷均未能使Zr-4合金基体暴露,涂层能够形成有效壁垒,防止锆合金基体暴露造成核事故,阻止基体进一步被破坏。     

Cr涂层锆合金包壳高温蒸汽氧化动力学及微观机理研究

Cr涂层锆合金包壳具备抗高温蒸汽氧化性能优异、耐腐蚀和耐磨蚀性能良好、工程应用难度较小等特点,成为最具前景的近期型事故容错燃料候选材料之一。本工作以Zr-1Nb合金管为基体材料,采用磁控溅射工艺制备均匀致密Cr涂层,涂层厚度范围12～15μm。通过同步综合热分析仪开展双面高温蒸汽氧化试验,氧化温度为1000、1100和1200℃,氧化时间为300～5000s,系统研究反应堆事故工况下Cr涂层锆合金包壳高温蒸汽氧化行为。采用扫描电子显微镜、能谱仪和X射线衍射仪表征高温氧化产物膜微观形貌特征、氧化层厚度、元素分布以及物相组成等,建立Cr涂层氧化动力学模型,探讨高温氧化机理。研究表明,高温蒸汽环境中,Cr涂层锆合金包壳外壁形成致密Cr2O3层,有效阻止O元素扩散至Zr合金基体,从而提升复合包壳的耐高温性能。其次,Cr涂层高温蒸汽氧化动力学曲线遵循抛物线规律,氧化速率常数比锆合金低大约2个数量级,显著提升锆合金包壳抗高温蒸汽氧化性能。     

预处理工艺对电镀制备的Cr涂层Zr-4合金的微结构和结合强度的影响

采用电镀技术在锆合金基体上成功制备出了优异微结构和高结合强度的Cr涂层。分析了不同预处理工艺制备的涂层表面和涂层与基体界面的微结构特征,并利用划痕法测试了涂层与基体的结合强度。结果表明:预处理工艺显著影响涂层粒径尺寸和界面微结构,采用活化处理和预镀镍可以获得平均粒径为0.52μm的致密Cr涂层。活化处理使Cr/Zr界面产生实质性的微观结合,尽管预镀镍层改善了界面微结构,但依然存在少许纳米尺度的微观缺陷。热处理使Ni和Zr原子相互扩散形成Ni_xZr_y金属间化合物的冶金结合的同时,最终消除了界面处的纳米级微观缺陷(如空洞、气泡、杂质与微裂纹等),从而制备出了具有Cr/Ni/Ni_xZr_y/Zr多层结构的Cr涂层Zr-4合金。Cr涂层与Ni层以晶格匹配的方式结合,Ni_xZr_y为多层结构,从Ni层到Zr-4基体依次为Ni_5Zr、Ni_7Zr_2、Ni_3Zr、Ni_(10)Zr_7、NiZr和NiZr_2相层。活化处理大幅度提升涂层与基体间的结合强度,界面结合强度由未活化的1.9 N提高到活化后的48.2 N,预镀镍进一步提高到75.8 N;而热处理形成的Ni_xZr_y为硬度较高的多层金属间化合物层,使结合强度略有降低。     

核电耐事故锆包壳表面涂层研究进展

锆合金表面涂层作为一种短期内最易于实现商业化工程应用的耐事故包壳材料,已成为国际上新型核电燃料元件研发的热点。综述了近年锆包壳表面涂层研究已取得的重要研究成果。阐述了锆合金表面涂层材料的发展,包括MAX相、Cr系、陶瓷和FeCrAl合金等,重点分析了金属Cr因易于获得高质量涂层,且具有优异的耐腐蚀、耐高温氧化等性能,成为耐事故锆包壳表面涂层的首选材料。讨论了锆合金表面Cr涂层沉积技术的发展,包括物理气相沉积法、冷喷涂、激光熔覆和等离子喷涂等,着重分析了不同的科研机构均形成了各自的涂层锆管研发路线。评价了锆包壳表面Cr涂层的关键应用性能,重点分析了高温氧化–脆化、腐蚀、环压、磨损以及高温爆破等条件下的表面涂层效应。水蒸气环境中表面Cr涂层可有效阻止氧元素向锆基体的扩散,高温氧化–淬火后锆基体内残留了大量β–Zr相,涂层锆管仍具有一定的残余塑性;小变形工况下表面Cr涂层与锆基体间具有良好的膜基协同变形能力;Cr涂层对锆管基体具有一定的表面强化效应,一定程度上可改善涂层锆管的高温爆破性能;堆内辐照后Cr–Zr界面成分、微结构稳定性良好,21%环向肿胀后表面Cr涂层依然未剥落。最后,总结与展望了锆包壳表面Cr涂层的科研成果与研究方向。     

锆合金包壳Cr涂层界面元素扩散行为研究进展

随着核反应堆向高燃耗和更长服役寿命方向发展,对包壳材料的安全可靠性提出了更高的要求。锆合金表面Cr涂层由于其优异的抗高温氧化性能、耐腐蚀性能以及与基体良好的兼容性,被认为是最有前景的耐事故涂层包壳材料。综述了近年来涂层Cr与基体Zr界面元素扩散行为的研究成果,重点介绍了Cr涂层不同状态下的界面结构及演变规律,包括沉积、退火、辐照、氧化等状态。总结了Cr的扩散、分布和金属间化合物Zr-Cr-(Fe)层的生长动力学模型,归纳了界面扩散对涂层结构及性能的不利影响。扩散阻挡层是一种抑制涂层与基体互扩散的有效结构,介绍了阻挡层设计制备原则以及现有的和潜在的金属或陶瓷阻挡层材料,分析了2类典型阻挡层的优缺点。金属阻挡层能抑制Cr的扩散并延迟Cr-Zr共晶反应,但需要考虑中子经济性;虽然陶瓷阻挡层阻隔元素扩散的性能优异,但由于其与锆合金力学性能和热膨胀系数的差异明显,易产生微裂纹,需要考虑其抗裂性。最后提出了采用实验与分子动力学等相结合的多尺度研究方法开展界面研究,同时指出了目前研究工作中亟待解决的关键问题,这为后续的锆合金表面耐事故涂层研究与开发提供了重要参考。     

Au/Al_2O_3层状复合纳米涂层的制备及其抗氧化性能(英文)

采用磁控溅射法成功制备Al2O3/Au层状复合纳米涂层,所制备的涂层结构致密且由Al2O3层和Au层交替组成。采用高温循环氧化实验对复合涂层在不锈钢基体上的高温抗氧化性能进行分析评价。结果表明:Al2O3/Au层状复合纳米涂层极大地改善不锈钢基体的抗氧化和抗剥落性能。其抗氧化机理与涂层能够有效地抑制氧向合金基体的扩散并促进不锈钢基体中Cr元素的选择性氧化有关;抗剥落机理可归因于复合涂层中的Au层和纳米结构的Al2O3层能够有效地松弛高温热循环过程中产生的热应力,从而提高涂层的抗剥落性能。     

NiCoCrAlY粘结层喷涂工艺对8YSZ热障涂层抗氧化性能的影响

目的 提高热障涂层粘结层的抗高温氧化性能。方法 分别采用爆炸喷涂和等离子喷涂工艺制备了不同结构的NiCoCrAlY粘结层,之后通过等离子喷涂制备8YSZ陶瓷层,分析了两种粘结层结构的热障涂层的抗高温氧化性能。利用XRD、SEM和EDS对涂层物相、微观结构和成分进行分析,并对其与基体结合状态、抗高温氧化性能进行研究。结果 爆炸喷涂粘结层内部组织致密,缺陷较少,与基体结合处孔隙少;而等离子喷涂粘结层内部的层状特征明显,孔隙较多,表面粗糙度较低。爆炸喷涂粘结层氧化5 h后,表面生成了一层富Al2O3的致密氧化物膜;而等离子喷涂粘结层表面形成了富NiO、CoO、Cr2O3和Ni(Cr,Al)2O4的氧化物层,并出现了许多微裂纹和片层状氧化物。爆炸喷涂制备的热障涂层试样在前5 h氧化增重速率高于等离子喷涂试样,随后变平缓,而等离子喷涂试样氧化速率依然较高。爆炸喷涂热障涂层的热生长氧化物层（Thermally grown oxide, TGO）经50 h氧化后,仍呈连续状,厚度均匀,粘结层内氧化物缺陷较少。结论 爆炸喷涂粘结层组织均匀、致密,喷涂时涂层的氧化以及热处理的内氧化较少,使得足够的Al较快速地在粘结层表面形成致密的氧化铝,表面一定厚度的氧化铝层抑制了氧和其他金属原子的相向扩散反应,提高了涂层的抗高温氧化性能。     

Cr23C6-NiCr涂层制备及其高温氧化行为

针对传统高温防护涂层在长期服役环境中可靠性不足等问题,设计了新型Cr23 C6- NiCr金属陶瓷体系,并采用超音速火焰喷涂(High Velocity Oxy-fuel Spraying,HVOF)技术制备了相应复合结构涂层.利用XRD、SEM和高温电阻炉等设备,对比研究了其与传统Cr3 C2 - NiCr金属陶瓷涂层的微观组织结构特征及高温氧化行为.结果表明,复合涂层具有HVOF喷涂涂层典型的致密层状结构,喷涂过程中无明显相分解或氧化物生成.两种涂层在经过800℃循环氧化后具有相似的氧化动力学曲线,表面生成均匀致密的Cr2 O3钝化膜阻止了氧原子向涂层内部的扩散,起到了较好的隔离防护作用,呈现出较为优异的抗高温氧化性能.     

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。