High temperature oxidation characteristics of Nb–10W–XCr alloys

The effect of Cr content on the microstructure and cyclic oxidation behavior of Nb–10W–XCr alloys with four different compositions has been investigated. Experiments were conducted in air at 900 °C and 1300 °C; the oxidation kinetics have been evaluated in terms of weight change per unit area with respect to exposure time. Alloy's microstructure consists of Nb solid solution phase regions surrounded by a network of NbCr₂ Laves phase. A trend of improvement in oxidation resistance with increase of the intermetallic phase is observed at 1300 °C and oxidation kinetics follow a parabolic behavior. At 900 °C, alloys with higher Cr content exhibit higher oxidation rates than alloys with lower Cr content. The oxidation products are a mixture of CrNbO₄, and Nb₂O₅ and the amount of each oxide present in the mixture is related to the intermetallic phase content. Results delineate the influence of microstructure and composition on the oxidation mechanisms of these alloys that represent a promising base for high-temperature intermetallic alloy development.     

UO2-(Zr0.8Ca0.2)O1.8面心立方固溶体微球制备工艺研究

为研制出耐辐照的新型单相陶瓷燃料,采用溶胶-凝胶法,通过复合溶胶配制、分散胶凝、洗涤、干燥煅烧与烧结过程,开展了UO2-(Zr0.8Ca0.2)O1.8燃料微球制备工艺研究,制备出铀摩尔分数含量分别为30mol%、50mol%、70mol%的UO2-(Zr0.8Ca0.2)O1.8燃料微球样品。在对工艺过程进行分析的基础上,通过实验确定了工艺参数。采用X射线衍射（XRD）对3种燃料微球样品进行分析,分析结果表明:铀摩尔分数含量分别为30mol%、50mol%、70mol%的UO2-(Zr0.8Ca0.2)O1.8燃料微球样品均为面心立方（FCC）固溶体结构。      

Formation of deformation bands and precipitation of Ni3Al(γ′) phase in NiAl(β)-based single crystals by thermomechanical processing

Microstructure and crystal orientation distribution of two-phase NiAl(β)/Ni₃Al(γ′) alloys obtained by thermomechanical processing were investigated. Cylindrical Ni-36 and 38 at.%Al alloy single crystals with various initial loading axes were hot-compressed at a high strain rate of 1.0 s⁻¹ and subsequently annealed in the (β/γ′) two-phase region. After the hot deformation, relatively uniform subgrain structures were formed in initial 〈111〉_β-oriented crystals, while a number of deformation bands perpendicular to the compressive axis developed in 〈100〉_β-, 〈110〉_β- and 〈123〉_β-oriented crystals. Two types of deformation bands with different crystal orientations were alternately arranged against the compressive axis. After annealing in the (β/γ′) two-phase region, a film-shaped γ′ phase with peculiar variants of the Kurdjumov–Sachs orientation relationship preferentially precipitated along the boundary between the deformation bands, resulting in the formation of a (β/γ′) two-phase lamellar structure. Formation process of the deformation bands in β phase and the crystallography of γ′ precipitates along deformation bands were discussed.     

UF_6气化水解工艺改进研究

介绍了湿法UF_6气化水解过程,研究了不同气化水解过程中的压力选择、气化速率与水解速率的关系、水解工艺对水解速率的影响、水解工艺对水解液温度的影响,以及不同气化水解工艺所需热量。结果表明:UF_6气化速率与水解速率成正比,水解速率为影响UF_6气化水解的主要因素;改进后的气化水解工艺有利于提高UF_6气化水解效率。     

难熔高熵合金在反应堆结构材料领域的机遇与挑战

传统反应堆结构材料性能已趋于极限,亟需开发新型材料。难熔高熵合金是以多种难熔元素作为主元的新型金属材料,具有独特的力学、物理和化学性质,尤其在高温力学、抗辐照等方面表现出优异的性能。难熔高熵合金在第4代核裂变反应堆包壳材料、核聚变堆面向第一壁材料等关键领域具有广阔的应用前景。本文结合具有代表性的文献,围绕难熔高熵合金的力学性能、抗辐照性能、抗氧化性能阐述了其强化机制与抗辐照机理,梳理了难熔高熵合金的发展脉络,在此基础上展望了难熔高熵合金在反应堆结构材料领域的应用前景。     

内壁强化对TA16钛合金传热管断裂韧度的影响EI北大核心CSCD

采用TA16传热管制备的直流蒸汽发生器是新一代核动力装置的核心部件。为提高管材的内壁质量,目前采用内绞、喷砂等数道表面加工程序,生产成本大幅升高。为简化工艺流程,降低生产成本,开展针对TA16管材的内壁强化技术研究。同时为了确定内壁强化对管材断裂韧性的影响,提出一种含双边轴向裂纹管(DEAT)试样,通过弹塑性有限元分析建立DEAT试样的应力强度因子K和J积分的计算表达式,通过建立的试验方法完成内壁强化前后TA16传热管的J-R曲线测试,获得内壁强化前后TA16传热管的断裂韧性参数。试验后采用SEM、EBSD、TEM及纳米压痕分析内壁强化对管材微观组织和性能的影响。研究结果表明:强化后TA16管内壁从表面沿径向形成100~200μm的纳米超细晶区和孪晶变形区,显著提高了管材的内壁质量,但由于表层的硬度升高,导致传热管的断裂韧度整体水平有所下降。研究结果可为TA16管材的质量提升、安全性评价及性能退化评估奠定技术基础。     

Pressure-assisted flash sintering of ZnO ceramics

Implementing pressure-assisted flash sintering of ZnO powder without pretreatment by a new experimental configuration is presented. Rapid and energy-concentrated heating of electrode-sample-electrode area by induction heating allows preheating and flash sintering of loose-pack powder in the die with pressure assistance. Using an insulated die enables the current to flow through the sample during flash sintering. ZnO ceramics with a relative density of 95.1% can be achieved in less than 3 min. The whole process includes 104 s of preheating by a low-power induction heating device and 30 s of flash sintering assisted by a pressure of 26 MPa using the pulsed direct current (DC). The process characteristics of pressure-assisted flash sintering using the pulsed DC are discussed. The effect of pressure on densification and grain size is analyzed in detail, and some potential mechanisms are provided.     

Microstructure and Tensile Strength of the Bonded Interfaces and Parent Materials in W/ODS Steel Joints Fabricated by Direct SSDB

In the present work, Tungsten (W)/oxide dispersion strengthened (ODS) steel joints were fabricated by the direct solid state diffusion bonding (SSDB) technology with a multistage cooling process, and the microstructure and tensile strength of the bonded interfaces and parent materials were experimentally investigated. The results show that W and ODS steel can be successfully bonded at the temperature ranging from 900 °C to 1050 °C, without severe macroscopic deformation or obvious microscopic defects. Reaction layers generated at the bonded interfaces are evolutive with the bonding temperature, result in different fracture locations of the bonded joints. In the joint bonded at 950 °C, a higher interfacial strength of ~ 234.2 MPa is achieved, due to the formation of nano-scale intermetallic compound FeW. Microstructure of W remains stable after all the SSDB processes, while the lath structure of ODS steel is completely broken and transformed into the equiaxed grains, which should be responsible for the deterioration of strength. When the bonding temperature is higher than 950 °C, the pinning effect of precipitates M₂₃C₆ and nano-oxide particles on the movement of dislocations is observed.