Gd2 O3 -Yb2 O3 -Y2 O3 -ZrO2 热障涂层材料的热物理性能

目的：通过多元稀土氧化物掺杂改性YSZ,提高传统热障涂层的性能。方法使用化学共沉淀法制备不同掺杂量的Gd2 O3-Yb2 O3-Y2 O3-ZrO2( GYYZO)材料,并分别使用冷等静压-烧结和等离子喷涂工艺制备块材和涂层。通过测试块材的热导率和热膨胀系数,分析评价材料的热物理性能。对高温退火处理后的涂层进行X射线衍射分析,评价不同成分涂层的高温相稳定性。结果氧化锆基材料的热导率和热膨胀系数随总掺杂量升高而降低。氧化锆中稀土氧化物总掺杂量为5.5%~9.84%(摩尔分数)时,在1000℃下的热导率为1.25~1.56 W/(m·K),相对8YSZ材料下降了22%~37.5%；在200~1300℃的热膨胀系数为(10~11.1)×10-6/K,与传统8YSZ材料相当。在1400℃长时间退火处理后,低掺杂量GYYZO涂层中的单斜相含量明显低于8 YSZ涂层。结论多元稀土氧化物掺杂改性氧化锆材料具有良好的高温相稳定性、低热导率和适当的热膨胀系数,可以作为高性能热障涂层的备选材料。  

Phase-stability dependence of plastic deformation behavior in Ti-Nb-Ta-Zr-O alloys

The authors investigated the effects of alloy content on mechanical properties to make clear a correlation between plastic deformation behavior and β-phase stability in Ti-Nb-Ta-Zr-O alloys. It was realized that there was specific compositional area in which the alloy exhibited little work hardening and minimum Young’s modulus value. The specific area was expressed by the bond order (Bo), based on theDV-Xα method, of 2.87 and the averaged electron/atom ratio (e/a) of 4.24, which corresponded to those of a multifunctional β titanium alloy, “Gum Metal.” These electronic conditions also minimized ideal strength required for plastic deformation without any dislocation activity. The deformation behavior of alloys in the specific compositional area revealed that the unique behavior could be characterized by a “giant fault.” It was also confirmed that such a compositional area corresponded to the phase boundary between the α″ martensite and β phases at room temperature. This paper was presented at the Beta Titanium Alloys of the 00’s Symposium sponsored by the Titanium Committee of TMS, held during the 2005 TMS Annual Meeting & Exhibition, February 13–16, 2005 in San Francisco, CA.  

奥氏体型Fe-Cr-Mn(W,V)合金相稳定性研究

通过形变加工和长期时效热处理 ,研究了 (C N)复合强化的Fe 13Cr 17Mn(W ,V)奥氏体合金的稳定性和相平衡特点。结果表明 :在 50 0℃以下合金奥氏体稳定 ,不发生γ→α转变。采用 (C N)复合添加晶粒细化 ,可有效抑制ε马氏体形成和σ相析出。 50 0～ 70 0℃长期时效后形变诱发大量碳化物析出 ,MS 点提高 ,加快形变诱发α′马氏体分解和再结晶 ,促使γ→α转变和σ相析出 ,合金奥氏体变得不稳定  

Phase equilibria and microstructural control of gamma TiAl based alloys

Phase equilibria among the β (bcc or B2), (hcp) and γ (L1₀) phases in Ti---Al---M ternary systems at elevated temperatures have been studied, where the M is β stabilizing element for pure titanium. The β(B2) + + γ three-phase coexisting region exists at temperatures above 1473 K, and it moves towards a direction of high aluminum and high M concentrations with increasing temperature. The change in the phase equilibria by the addition M is associated with the ↔ β allotropic transformation temperature of pure titanium and can be thermodynamically interpreted in terms of the lattice stability ratios of M to Ti. The change in the phase equilibria results in new reaction pathways peculiar to the ternary systems, thereby opening more possibility for microstructure control of the gamma based alloys. The vertical section drawn based on these studies demonstrates that the γ phase can be in equilibrium with the β(B2) phase at relatively low temperatures in the ternary systems and create a reaction pathway of → β(B2) + γ. Upon cooling along the same pathway of → γ as in the binary alloy, the addition of third element affects the transformation rate, and the massive γ structure is found to be formed even under slow cooling rate.  

分子轨道理论在分析合金相稳定性方面的应用

应用分子轨道理论分析了面心立方过渡族金属三元合金的固溶度,采用特征点成分平均法计算了三元合金相图的不同等温截面的43个γ/(γ+σ),γ/(γ+μ),和γ/(γ+γ′)相界线的临界■_d值■_(dc)。得到了γ/(γ+μ)相变的■_(dc)值与温度的关系式,并对分析的准确度进行了讨论发现存在着临界平均键合级次■_(oc),它可以和■_(dc)一道用来分析合金相的稳定性。  

亚稳奥氏体型Fe-Cr-Mn(W,V)合金的组织稳定性研究

通过对形变奥氏体组织进行长期时效观察合金相演化过程 ,研究了低放射性亚稳奥氏体Fe Cr Mn(W ,V)合金的组织稳定性。实验表明 :合金在高于 40 0℃时 ,相平衡处在γ α σ三相区 ,低于 40 0℃可以保证亚稳奥氏体的稳定性。亚稳奥氏体可以发生γ→ε→α′→α转变也可以发生γ→γ(f)→α′(f)→α转变 ,ε马氏体不是γ→α转变的唯一中间过渡相。形变诱发ε马氏体形成过程中伴随奥氏体晶粒碎化 ,可产生细晶强化作用 ,这是开发亚稳奥氏体Fe Cr Mn合金的重要途径。  

Some Aspects of the Hot Corrosion of Thermal Barrier Coatings

This paper reviews the hot corrosion of zirconia-based thermal barrier coatings for engine applications. Emphasis is placed on understanding the chemical reactions, and such other mechanisms as can be iden-tified, that cause corrosive degradation of the thermal barrier coating. The various approaches taken to improve the hot corrosion resistance of thermal barrier coatings are also briefly described and critiqued.  

FeTiCoNiVCrMnCuAl系高熵合金中金属间化合物的第一性原理计算（英文）

利用第一性原理研究FeTiCoNiVCrMnCuAl系高熵合金中常见的金属间化合物的结构、电子和弹性性质。形成焓和结合能计算结果表明：FeTi、Fe2Ti、AlCrFe2、Co2Ti、AlMn2V和Mn2Ti相有可能在高熵合金形成的过程中出现。进一步研究发现,FeTi、Fe2Ti、AlCrFe2、Co2Ti和AlMn2V相具有较高的剪切模量和弹性模量,在高熵合金中可能作为增强相增加合金的强度。通过研究分波的态密度来揭示中间相的键合作用,并研究p-d杂化的强度,揭示中间相的弹性特征的潜在机理。  

Ti-Nb合金β结构稳定性和弹性性质

采用基于密度函数理论的缀加平面波加局域轨道（APW＋lo）方法和超晶胞方法对Nb含量为6.25%～37.5%Nb（摩尔分数）的Ti-Nb二元合金的能量、电子结构以及弹性性质进行了理论计算,研究Nb含量对Ti-Nb合金的β结构稳定性和弹性性质的影响。结果表明,随着Nb含量的升高,Ti-Nb合金的β结构稳定性提高,正方剪切常数C＇以及弹性模量K、E和G呈单调增加。当Nb含量为9.87%时,正方剪切常数大于并接近于零,此时Ti-Nb合金的β结构稳定性最低,并具有最低的弹性模量。  

Atomistic simulation on the structural properties and phase stability for Cr23C6 and Mn23C6

Based on the successful applications of lattice inversion method in many fields, the crystal structure and phase stability of Cr₂₃C₆ and Mn₂₃C₆ are investigated using the interatomic potentials obtained by lattice inversion method in this research. The calculated atomic coordinates and crystal parameters are in good agreement with the experimental results and the phase stability of Cr₂₃C₆ and Mn₂₃C₆ are tested by random atom shifts and global deformations. The calculated energy also indicates that the Cr₂₃C₆ is more stable than Mn₂₃C₆.