ODS铁素体钢中弥散氧化物的研究进展

ODS 铁素体钢具有优异的高温力学性能和抗辐照能力, 有望成为新一代先进反应堆如超临界水堆包壳管的候选材料以及未来聚变堆的结构材料.ODS铁素体钢的这种优异性能主要源于其内部弥散分布的细小氧化物颗粒.回顾了国内外所涉及的关于ODS铁素体钢中氧化物弥散强化颗粒的研究进展,包括氧化物弥散粒子的选择、检测、分解和析出机理、存在形式等,展望了目前ODS铁素体钢的应用前景并总结了存在的问题.     

ODS钢在热加工过程中纳米氧化物演化行为的研究进展

与第二、三代核能系统相比,第四代核能系统和核聚变堆的运行温度更高、辐照剂量更强以及腐蚀环境更为严苛,因此开发高性能核电材料迫在眉睫。氧化物弥散强化(Oxide dispersion strengthened,ODS)钢含有高密度的弥散纳米氧化物和空位尾闾,使其具有优异的抗高温蠕变和抗辐照肿胀的性能,因此被认为是第四代核裂变堆包壳管和核聚变堆包层结构最有前景的候选材料之一。ODS钢优异的性能源于其独特的微观组织结构,尤其是弥散分布的纳米氧化物。在热变形过程中,纳米氧化物形态变化不大,但在冷变形过程中,纳米氧化物会发生明显的塑性变形,后续的高温退火处理使其溶解再析出。合理调控合金元素可以提高纳米氧化物的稳定性和减小纳米氧化物尺寸,但晶界与纳米氧化物的相互作用会使纳米氧化物丧失界面关系而加速粗化,并且在晶界附近区域会出现无析出区。由于ODS钢中纳米氧化物的演化行为复杂,调控纳米氧化物的尺寸和弥散分布程度仍有待进一步研究。本文归纳了ODS钢在热加工过程中纳米氧化物演化行为的研究进展,分别对纳米氧化物的塑性变形机制、纳米氧化物的溶解再析出机制、纳米氧化物的热稳定性和纳米氧化物与晶界的相互作用进行...     

先进核能系统用ODS钢的显微组织设计与调控研究进展

核能是一种重要的清洁能源,目前正在大力发展具有更高安全性和经济性的第四代反应堆及聚变堆,与当前商用反应堆相比,其工作温度更高,辐照剂量更强,传统的锆合金及不锈钢已不能满足未来先进反应堆苛刻的服役环境,具有优异综合服役性能的关键结构材料的研发成为制约先进核能工程应用的瓶颈之一。通过机械合金化等先进粉末冶金方法可以向钢基体中引入数密度极高的超细纳米氧化物粒子,所制备的纳米氧化物弥散强化(Oxide dispersion strengthened,ODS)钢具有比同类熔炼钢更优异的高温蠕变强度以及抗辐照性能,从而具有更高的服役温度窗口,因而被确定为多种第四代反应堆包壳和未来聚变堆包层结构的重要候选材料,成为国际核材料领域研究的热点。ODS钢的优异性能源于其成分设计和采用先进粉末冶金工艺形成的独特的显微组织,即亚微米的超细晶粒组织以及在晶内弥散分布的平均尺寸仅为几纳米、数密度高达1023m-3的氧化物粒子或团簇,这些弥散相具有极高的热稳定性及抗辐照稳定性,可以起到有效的位错钉扎强化作用,从而明显提高材料的高温强度及服役温度上限;而大量的弥散粒子与基体之间形成的界面可以对辐照引起的缺陷及气泡进行有效捕获,显著提高材料的抗辐照肿胀性能。满足服役性能要求的显微组织的设计和有效调控是制备高性能先进材料的核心,而显微组织又明显受控于成分设计、制备技术及工艺参数。虽然近年来关于ODS钢的研究日益活跃,但是由于ODS钢显微组织及制备工艺过程的复杂性,在成分设计与微纳显微组织的调控及其与服役性能的匹配和相关机理方面,依然存在许多制约ODS钢实际工程应用的基础性问题。本文针对制约先进核能系统用ODS钢应用的基础核心问题,把握ODS钢显微组织特点及其与成分设计和制备技术之间的关系这一主线,就国内外关于ODS钢显微组织及其分析手段、氧化物弥散粒子的特点及其高温时效和辐照稳定性、成分设计和制备技术对显微组织的影响等研究内容进行总结和分析,对ODS钢的应用前景和存在的问题进行总结和展望,为满足先进反应堆服役环境的ODS钢的发展提供参考。     

ODS钢的抗辐照设计及纳米第二相粒子表征的研究进展

先进裂变反应堆及聚变堆要求材料在高温高压、强中子辐照、长服役周期等苛刻服役环境下具有卓越的结构和性能稳定性。氧化物弥散强化(ODS)钢由于具有优异的耐高温及耐辐照性能成为第四代反应堆包壳及核聚变包层最有希望的候选材料。基于材料的中子辐照损伤特性,主要介绍了ODS钢的抗辐照设计及纳米第二相粒子的表征方面的研究进展。     

15-15Ti ODS奥氏体钢晶粒组织与纳米粒子的透射电镜表征

15-15Ti奥氏体不锈钢由于其优异的耐腐蚀性能和高温力学性能成为钠冷快堆包壳的候选材料,其高温力学性能和抗辐照肿胀能力可以通过氧化物弥散强化(ODS)进行增强。本工作对通过机械合金化以及锻造工艺制备的15-15Ti ODS奥氏体钢和作为参比材料的15-15Ti奥氏体钢的微观结构进行研究,对ODS钢中氧化物颗粒的分布以及强化机制有了较为深入的认识。研究发现氧化物弥散粒子分布总体均匀但有成团聚集倾向。Y-Zr-O粒子的平均粒径为(9.97±0.04) nm,平均粒距为(17.25±0.68) nm,数密度约为4.49×10²²m^-3。在透射电镜明场像下观察到ODS样品中氧化物颗粒对位错的钉扎作用。扫描透射(STEM)结合能谱分析显示ODS样品中有两种氧化物,分别为占比较少的Al₂O₃以及占比较多的Y₄Zr₃O₁₂。高分辨电镜表征发现第二相粒子与基体之间出现共格或半共格界面的迹象,并且少数粒子周围出现非晶化界面。     

ODS钢中纳米氧化物颗粒成分与结构研究

采用透射电镜和层析原子探针(APT)分析了9Cr-ODS钢中纳米氧化物颗粒成分和结构。研究发现,氧化物颗粒成分与其大小有一定的关系,可将其归纳为3类:(1)氧化物5nm,m(Y)∶m(Ti)1,可能是非整比化合物;(2)5~10 nm氧化物尺寸40nm,m(Y)∶m(Ti)≈1,可能是Y2Ti2O7;(3)氧化物40 nm,为TiO2。Cr在氧化物周围偏析形成壳状结构。     

氧化物弥散强化高温合金抗氧化性能的研究进展

氧化物弥散强化商业高温合金因氧化物颗粒在基体中的弥散强化作用而具有较好的高温力学性能,如今被广泛应用于航空航天、能源、汽车等领域的高温部件。研究发现,氧化物颗粒的掺杂不仅可以使合金基体具有优异的高温强度,还可以显著提高基体的抗氧化性能。概述了氧化物颗粒种类、尺寸和含量对高温合金抗氧化性能的影响,从合金初期氧化行为、氧化膜生长速度、生长机制、粘附性能等角度重点关注不同性质氧化物(如活性元素氧化物和非活性元素氧化物)弥散质点在氧化过程中作用机理的异同,最后对未来的研究方向做出了展望。     

通过离子掺杂剂界面偏析来提高氧化物弥散强化合金的机械性能

氧化物弥散强化钨合金(ODS-W)因具有显著提升的抗辐照能力、高温强度以及抗蠕变性能而展现出巨大的高温应用潜力.然而,分散在合金中的氧化物第二相颗粒容易在钨晶界处团聚并长大(甚至到微米尺寸),这大大抑制了它们对钨合金的强化效果.目前,如何有效细化和分散钨晶界处的氧化物第二相颗粒一直是人们面临的巨大挑战.在本文中,我们通...     

14CrODS铁素体钢的制备及其拉伸性能

通过机械合金化制备了成分(质量分数/%)为Fe-14Cr-0.5Ti-0.35Y2O3的氧化物弥散强化合金粉末,机械合金化后粉末内部各合金元素分布均匀。采用热等静压的方法制得14CrODS铁素体钢,并对其进行锻造和热处理。与未添加氧化物弥散颗粒的14CrNA相比,14CrODS钢的强度有明显提高,但是与MA957有一定差距,抗拉强度有待改进;与MA957相比,14CrODS表现出良好的塑性,锻造可进一步提高14CrODS的高温塑性,但是锻造过程中的残余应力使材料低温拉伸时呈脆性,退火可去除残余应力,极大地提高14CrODS的塑性,使其远优于MA957。     

化学法制备ODS钢的新工艺技术

氧化物弥散强化(Oxide Dispersion Strengthened,ODS)铁素体钢,由于其优异的高温力学性能和良好的抗辐照能力被认为是快堆与超临界水堆燃料包壳管候选材料之一。传统ODS钢的制备方法是采用机械合金化法向铁素体钢中添加高熔点弥散细小的氧化物Y2O3而具有优良的高温强度,但合金的塑性和冲击韧性较差,热加工中存在严重的组织和性能各向异性,给合金制备或薄壁管带来极大的困难。     

Nanospray mass spectrometry technique for analysing nanomaterials from molecular precursors up to 1.5 nm in diameter cluster

A mass spectrometry method (nanospray mass spectrometry [NMS]) for analyzing nano-scale materials and their precursors is described. We show that both positive and negative ionic modes in NMS are promising as they provide insight concerning the structure analysis, the composition and the stability of materials up to 1.5 nm in size.     

Microstructural changes upon annealing in ODS-strengthened ultrafine grained ferritic steel

In this study, the stability of grain size and oxide nanoparticles in the ODS steel upon annealing at high temperature (650–1350 °C) has been evaluated. The ODS Fe–Cr–W–Ti–Y₂O₃ steel has been manufactured by powder metallurgy, consolidated by hot isostatic pressing and processed by hydrostatic extrusion. Such a processing brings about ultrafine grain structure reinforced with oxide nanoparticles (few nm in diameter) and results in superior mechanical properties. The stability of nano-oxides has been analyzed by small angle X-ray scattering together with transmission electron microscopy. The results obtained revealed excellent thermal stability of ultrafine grained ODS ferritic steel, which was attributed to the resistance of oxides against coarsening.     

掺杂合金元素法抑制金属中氦脆的研究进展

聚变堆结构材料极易因α粒子和中子辐照引入大量的He原子而脆化,降低核设施的稳定性和安全性,因此必须提高材料的抗氦脆能力.添加合金元素法是一种有效抑制金属中氦脆的方法.然而,合金元素对金属中的氦脆抑制效果受到原子占位情况、原子尺寸大小、浓度、温度等因素影响.因此,掺杂合金元素时必须考虑合金元素的种类和含量,并辅以一定的热处理.回顾了掺杂合金元素法抑制金属中氦脆的研究进展,简要分析了影响合金元素在金属中氦行为角色的因素.     

Microstructure characterisation and tensile properties of 18Cr-4.5Al-0.3Zr- oxide dispersion strengthened steel

The 18Cr–4.5Al–0.3Zr–oxide dispersion strengthened (ODS) steel was fabricated by mechanical alloying (MA) and spark plasma sintering (SPS) technique. A microstructural characterisation was performed on an 18Cr–4.5Al–0.3Zr–ODS steel using high angle annual dark field (HAADF) and synchrotron small angle X-ray scattering (SAXS). HAADF and SAXS results showed that high-density nanoscale oxides are formed in 18Cr–4.5Al–0.3Zr–ODS steel. The oxides in the specimen can be roughly divided into two categories according to their compositions: (1) core/shell structure oxides with Al–O oxide cores and Y shells; (2) nm-scale trigonal-phase Y₄Zr₃O₁₂ oxides. In addition, tensile testing results revealed that the specimen exhibited better tensile strength and ductility as compared with another commercial ODS steels with similar composition.     

Structure and composition of oxides in FeCrAl ODS alloy with Zr addition

FeCrAl ODS (oxide dispersion strengthened) alloy with Zr addition was investigated with the main focus on the structure and composition of oxide particles. The results reveal that almost all the small particles (diameter <2?nm) were found to be consistent with trigonal δ-phase Y₄Zr₃O₁₂, with cubic Y₃Al₅O₁₂ (YAG) oxides occasionally detected. The large particles (>2?nm) were mainly identified as monoclinic Al₂O₃ oxides. A core/shell structure is found in slightly large oxide particles. Oxide cores are Al and O while shell regions are enriched in Y. This leads us a promising way to control the structure and size of the oxides and develop the high-performance FeCrAl ODS alloys.     

In-situ TEM observation of the evolution of helium bubbles &dislocation loops and their interaction in Pd during He+ irradiation

The microstructural evolution of purity Pd under 30 keV He+ irradiation at 573 K was investigated by in-situ transmission electron microscopy.The nucleation,growth,merging,annihilation,size change,number density variation,and types of dislocation loops were analyzed under the influence of irradiation fluence and sample thickness.Both perfect dislocation loops with b =1/2 < 110> and faulted dislocation loops with b =1/3 < 111> were formed.However,at low irradiation fluence,most of the loops were 1/3< 111> loops.The thickness of TEM foil obviously affected the ratio of 1 /3 < 111 > loop variants,the size and number density of dislocation loops,and the characteristics of bubble-loop complexes.With the increase of irradiation fluence,the size of dislocation loops increased,but loop volume number density remained almost constant until dislocation loops merged and evolved into dislocation network.There was an obvious interaction between dislocation loops and bubbles,indicating that 1 /3 < 111 > loop was first formed at the initial stage of irradiation,and when the loop grew to a certain size,obvious helium bubbles appeared inside its region.     

Influence of Metal Oxides on the Arc Erosion Behaviour of Silver Metal Oxides Electrical Contact Materials

In the present work investigations have been made to see the role of metal oxides on the performance of the silver metal oxides electrical contact materials. Silver metal oxide materials of three different compositions Ag-10CdO, Ag-7.6SnO2-2.3ln2O3 and Ag-10ZnO were prepared by internal oxidation process under identical processing conditions. These materials were tested for electrical conductivity, hardness, and erosion loss. Performing an accelerated test on the actual contactor assessed the electrical performance, involving erosion loss and temperature rise of the processed materials. The arc-eroded surface was characterized under scanning electron microscope. The study of the eroded surfaces of contacts indicates that the thermal stability of metal oxides depends on nature of silver-metal oxide interface and their mode of erosion. An attempt is made to correlate the surface features of the eroded contacts with the thermal stability of metal oxides.     

Phase transformations and phase-selective syntheses of aluminophosphate molecular sieves

A few aluminophosphate (AlPO) molecular sieves are synthesized hydrothermally under microwave irradiation and conventional electric heating. Less stable AlPO molecular sieves especially with large pore can be obtained preferentially in a short crystallization time because the inter-conversion of less stable phase into a more stable one is prohibited in short reaction time. The VFI transforms into AFI, and finally into APC, with the increase of reaction time since the relative stability is VFI < AFI < APC under the chosen reaction conditions. The relative stability can be explained with the pore size or by the framework density of each structure. Due to the rapid crystallization involved in the microwave method and instability of porous materials with large pore, these porous materials can be selectively synthesized by microwave irradiation. The synthesis of extra-large-pore VPI-5 using triethylamine is also reported for the first time, and the synthesized VPI-5 is very stable that can be dried at 100 degrees C at atmospheric pressure without the phase-transformation into AIPO-8.     

Characterization of the surface of bio-ceramic thin films

The biocompatibility and corrosion resistance of orthopaedic and dental implants are determined by their material composition and surface microstructural properties such as surface roughness, grain size, etc. Thin films of bio-inert materials such as oxides of Ti, Al, Zr, and bio-active materials such as hydroxy-apatite (Ca₁₀(PO₄)₆(OH)₂), compounds of calcium and phosphorous oxides are more attractive as bio-ceramic films because of their biocompatibility being higher, and toxicity being lower than those of the other materials. In this study, we mainly focused on characterization of the surface of bio-ceramics using atomic force microscopy (AFM). These films having a thickness of about 500 nm, had been processed using ion-beam sputter deposition, and ion-beam-assisted sputter deposition methods. Investigation of the surface of the films by AFM shows that irradiation with oxygen ions in the energy range of 3 keV increases the surface roughness. A detailed study of the grain size and roughness of several experimental cases of TiO₂ thin films showed that the films contained columnar grains with mean size of about 100 × 100 nm² grown in the z direction with a height of a few nanometers.