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1.
In this work, the interdiffusion between a MCrAlY-bond coat and two different nickel-based superalloys is evaluated at three temperatures, 950 °C, 980 °C, and 1,050 °C. Of primary interest is the evolution of Kirkendall-porosity, the β-depleted zone in the bond coat and the β’- depleted zone in the superalloy. The three phenomena arise near the interface between bond coat and superalloy as a result of interdiffusion between both materials and are detrimental to the coating-substrate system. The evolution of the interdiffusion phenomena is highly dependent on the alloy composition of the materials as well as the annealing temperature. It has been found that not only the temperature dependency of the diffusion coefficient but also the temperature dependent element activities are an important factor when evaluating the interdiffusion phenomena. It has further been shown that at lower temperatures the amount of Kirkendall-porosity per volume fraction is higher than at higher temperatures, even though the overall amount of porosity is lower. Different equilibrium concentrations of main alloying elements and a correspondingly lower over-saturation of vacancies have been identified as the main explanation. 相似文献
2.
Zr-4合金包壳包覆的U-Zr合金有望发展成为水冷反应堆的金属型核燃料。而燃料与包壳材料之间的相容性是反应堆安全运行的关键,但是,关于U-Zr合金燃料与Zr-4合金包壳材料界面元素扩散和反应的研究很少。为研究U-Zr合金与Zr-4合金之间的相容性和扩散行为,采用真空热压扩散法制备U-10wt.%Zr/Zr-4扩散偶,随后在高真空中580-1100℃高温热处理样品。采用扫描电镜和透射电镜分析检测扩散偶的界面微观结构和元素分布。系统研究了两种合金之间的相容性。δ-UZr2层和厚约20nm的富铀层形成于热压扩散法制备的样品界面。测量了合金界面扩散系数常数和扩散激活能,分别为4.23(±0.63)×10-6 m2/s和160.73(±1.67) kJ/mol。结果表明U-10wt.%Zr/Zr-4扩散偶的扩散系数大于U-Zr合金的,特别是在低温段。 相似文献
3.
4.
以Ti粉、纯Al和钛纤维为原料,采用压力浸渗法研制了Tif+Tip/Al复合材料,利用XRD和SEM测试分析了复合材料的相组成和显微组织,利用EDX测试分析了不同反应温度下纤维周围反应层中Al的浓度分布。计算了Ti和Al间的扩散系数,确定了扩散系数与温度和成分的变化规律,求出扩散激活能。结果表明,随着反应温度的升高,纤维周围的反应层厚度逐渐增大,各相的互扩散系数逐渐增大,各相的扩散激活能存在如下关系:Q_(Ti_3Al)〉Q_(TiAl_2)〉Q_(TiAl)〉Q_(TiAl_3)。 相似文献
5.
6.
利用先进分析透射电子显微镜,检测并系统地研究了磁控溅射Fe-Co薄膜与Al2O3基体之间的相互扩散。结果表明,扩散会形成尖晶石相FeAl2O4,并导致界面层的形成。微观结构表征表明,在界面附近的Fe-Co薄膜中形成了与相互扩散相关的非公度结构。本研究不仅检测到Fe-Co薄膜与蓝宝石基体之间的相互扩散和伴随的新相形成,而且揭示了界面区域相应的微观结构演变,这些结果可能对薄膜的磁学性质有很大的影响。 相似文献
7.
The III-V semiconductors are of great importance due to their applications in various electro-optic devices. The Al-Sb thin
film was deposited on glass substrate by thermal evaporation method at a pressure of 10-5 torr. The samples were annealed for 3 h at different constant temperatures in a vacuum chamber at a pressure of 10-5 torr. The electrical resistance vs temperature studies show phase transformation from metallic to semiconducting. The observed
positive thermoelectric power indicates that Al-Sb thin films arep-type in nature. The Rutherford back scattering analysis and optical band gap measurements also indicate that the inter-diffusion
concentration varies with temperature. 相似文献
8.
9.
Hiroshi Numakura Tatsuru Watanabe Makoto Uchida Yoko Yamabe-Mitarai Eisuke Bannai 《Journal of Phase Equilibria and Diffusion》2006,27(6):638-643
The diffusion in iridium-rich Ir-Nb alloys has been studied by single-phase interdiffusion experiments. The chemical diffusion
coefficient has been measured for the primary fcc solid-solution and theL12 ordered compound Ir3Nb in the temperature range between 1650 and 1950 °C, using Ir/Ir-8Nb and Ir-26Nb/Ir-28Nb diffusion couples, respectively
(numbers indicate mol%). While the chemical diffusion coefficient in the solid-solution phase is close to the tracer self-diffusion
coefficient of pure iridium, the diffusion in the compound phase is extremely slow: the chemical diffusion coefficient is
1/40 to 1/50 of that in the solid solution. The low diffusion rate in the compound must be beneficial for high-temperature
performance of refractory superalloys based on the Ir-Nb system.
This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was
held during TMS 2006, 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized
by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard
D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University. 相似文献
10.
Interdiffusion in hypothetical ternary single-phase and two-phase diffusion couples are examined using a phase-field model
by numerically solving the nonlinear Cahn-Hilliard and Ginzburg-Landau equations. For diffusion couples assembled with a regular
single-phase solution, constant chemical mobilities were used to examine the development of concentration profiles including
uphill diffusion and zero-flux plane. Zero-flux plane for a component was observed to develop for a diffusion couple at the
composition that corresponds to the activity of that component in one of the terminal alloys. Experimental thermodynamic parameters
and composition-dependent chemical mobilities were used to examine the morphological evolution of the interphase boundary
in solid-to-solid, two-phase diffusion couples. Instability at the interphase boundary was introduced initially (t=0) by a small compositional fluctuation at the diffuse interface, and its evolution varied largely as a function of terminal
alloys and related composition-dependent chemical mobility.
This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was
held during TMS 2006, the 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized
by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard
D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University. 相似文献