材料期刊网

Transmission Electron Microscopy Study of the Infrared Brazed High-strength Titanium Alloy

Z.Y. Wu R.K. Shiue C.S. Chang

材料科学技术（英文）

The transmission electron microscopy was employed to investigate the microstructure of infrared brazed high-strength Ti alloy using the Ti-15Cu-15Ni filler metal. Coarse primary Ti₂Ni and transformed β-Ti are observed in the 300 s brazed specimen. Blocky Ti₂Ni and eutectoid Ti₂Cu intermetallics are disappeared from the joint with increasing the brazing time to 1800 s. Both acicular α-Ti and retained β-Ti dominate the entire brazed joint.

关键词: Infrared Brazing , Ti , Ti-Cu-Ni filler , Microstructure

直流磁场对Mg-Y-C u-Z r合金结晶取向和性能的影响?

黄曼青 , 周全 , 刘峰 , 黄金角

材料导报 doi:10.11896/j.issn.1005-023X.2016.22.010

研究了0~1.4 T的直流磁场对陶瓷型铸造 Mg-Y-Cu-Zr 合金结晶取向和力学性能的影响。结果表明直流磁场对合金的初生相没有明显影响，但磁场强度大于1.12 T时，合金第二相的分布变得不连续。当磁场强度小于0.84 T时，α-Mg在(002)面的衍射峰逐渐增强，但变化不明显；当磁场强度大于0.84 T 时，α-Mg 基体在(002)、(101)面的衍射峰强度明显减弱，而在(100)晶面衍射峰强度有所增强。磁场处理后，合金的综合力学性能得到了改善；当磁场强度为1.4 T 时，其抗拉强度和伸长率最高，分别为237 MPa 和8.5%，较无磁场处理时分别提高了38.6%和33.4%。

关键词: 直流磁场 , Mg-Y-Cu-Zr合金 , 结晶取向 , 力学性能

MAGNETIC-PROPERTIES OF R2CO14(B,C) COMPOUNDS (R = Y, SM)

Journal of Applied Physics

The magnetic properties of R2Co14B1-xCx (x=0, 0.5 and R=Y, Sm) compounds have been studied by measuring the temperature dependence of the easy- and hard-magnetization curves on magnetically aligned samples between 1.5 and 300 K for Y2Co14(B,C) and at 4.2 K for Sm2Co14(B,C). The magnetic anisotropy of Y2Co14B increases due to the substitution of C for B, whereas the saturation magnetization decreases. Between 1.5 and 300 K, the anisotropy field of Y2Co14B0.5C0.5 increases about 2 T and the Co moment decreases about 0.05mu(B). The anisotropy field Of Sm2Co14B also increases upon C substitution and the saturation magnetization decreases slightly. The ac susceptibilities of both SM2Co14B and Sm2Co14B0.5C0.5 exhibit anomalies that may arise from a spin reorientation within the basal plane.

关键词: nd2fe14b;exchange;nd2co14b;r2fe14b;field

Studies of the changes of Mn-Y (Y = S, Se, Te) bond lengths R with the Mn composition x in Zn1-xMnxY alloys from optical spectrum data

Journal of Physics and Chemistry of Solids

The changes of Mn-Y (Y = S, Se, Te) bond lengths R with the Mn composition x in the diluted magnetic semiconductors Zn1-xMnxY are calculated from the optical spectra and their pressure shifts. The calculated results suggest that the Mn-Y bond lengths change little with the Mn composition x-much less than expected from lattice parameters as determined by X-ray diffraction. These results are also in good agreement with the observed values obtained from the EXAFS measurements. It appears that for ternary A(1-x)M(x)Y (M denotes the divalent transition-metal ion) alloys the changes of M-Y bond lengths R with the M composition x can be studied from their optical spectrum data. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词: semiconductors;high pressure;crystal fields;luminescence;light;properties;absorption fine-structure;local-structure;dependence;pressure;exafs

Secondary M6C precipitation in K40S cobalt-base alloy

Materials Letters

Secondary M,C precipitation was investigated in K40S cobalt-base alloy after 100 h aging at 950 degreesC. The results showed that it was closely related to the tungsten-rich zones inherited from the as-cast condition and the degeneration of the primary M7C3 carbide. A direct element reaction, 6M + C --> M6C, in which C comes from the decomposition of the M7C3 carbides, is suggested as the mechanism of secondary M6C precipitation in K40S alloy. (C) 2001 Elsevier Science B.V. All rights reserved.

关键词: M6C precipitation;aging;M7C3 carbide;superalloy

INTRINSIC MAGNETIC-PROPERTIES OF R2FE17CYNXCOMPOUNDS - (R=Y, SM, ER, AND TM)

Journal of Applied Physics

Samples of R2Fe17C(y)N(x) (R = Y, Sm, Er, Tm) were prepared by arc melting appropriate amount of R, Fe, and C, vacuum annealing at 1373 K and finally annealing at 740 K in nitrogen for 10 h. The magnetic properties of these compounds were investigated by means of ac initial susceptibility, magnetization measurements, and x-ray diffraction. The thermal stability of the nitride phase was studied by differential scanning calorimetry. It was found that, when heated above 600 K, R2Fe17C(y)N(x) irreversibly decomposes N which is irrespective of the carbon concentration and rare-earth element. The Curie temperatures of R2Fe17C(y)N(x) are independent of the carbon concentration and are approximately 400 K higher than those of the corresponding pure R2Fe17 compounds. However, the Curie temperatures cannot be correlated to the composition x of the initial R2Fe17C(y)N(x) compounds at room temperature because some N was lost during the heating to T(c). In the Er and Tm compounds spin reorientation transitions were found, marking the change of the easy magnetization direction from the c axis to the basal plane with increasing temperature. The Tm compounds show an additional magnetic transition at low temperatures (below 40 K). A coexistence of the hexagonal and the rhombohedral structural modifications was found in Er2Fe17C(y)N(x) when y < 1.5, characterized by two different spin reorientation temperatures. The anisotropy fields of Sm2Fe17C(y)N(x) are higher than that of Sm2Fe17N(x). Indications of a magnetic phase transition were found also in Sm2Fe17C0.7N(x) and Sm2Fe17C0.9N(x).

关键词: magnetocrystalline anisotropy;carbides;alloys

18R单相Mg-Y-Zn合金经773 K退火过程中14H LPSO相的析出行为

刘欢 , 严凯 , 晏井利 , 薛烽 , 孙甲鹏 , 江静华 , 马爱斌

中国有色金属学报(英文版) doi:10.1016/S1003-6326(17)60007-4

为了揭示14H相的形成机理，制备并研究了18R LPSO单相Mg?Y?Zn(简称S18)合金经773 K退火100 h的显微组织演变。结果表明：铸态S18合金主要由18R相组成(其体积分数高于93%)，并含有少量的W相和α-Mg相。退火时，S18合金中的18R相保持稳定，未转变成14H LPSO结构。然而，在α-Mg相内部形成了14H层片相，其尺寸和体积分数随着退火时间的延长不断增大。TEM分析表明，14H相在α-Mg内基面堆垛层错区域独立形核。14H层片的增厚生长是界面控制过程，与基面台阶的形成密切联系。而14H层片的伸长生长属于扩散控制，与溶质元素的扩散有关。该18R单相合金中14H相的形成机理可通过反应式α-Mg'→α-Mg +14H表示。

关键词: Mg-Y-Zn合金 , 18R LPSO相 , 14H LPSO相 , 高温退火 , 显微组织演变

Corrosion of Y, Fe and Fe-15Y in H-2-H2S mixture under 10(-3) Pa S-2 at 600 similar to 800 degrees C

材料科学技术（英文）

The corrosion of an Fe-based alloy containing 15 wt pet Y in H-2-H2S mixtures under 10(-3) Pa S-2 was studied at 600 similar to 800 degrees C in an attempt to find materials with improved sulphidation resistance with respect to pure Fe. The presence of Y has been shown to be beneficial, but not sufficient to the level expected. In fact, the alloy is able to form at all tested temperatures an external FeS layer, beneath which a zone containing a mixture of the two sulphides is also present. Thus, Fe can still diffuse through this region to form the outer FeS layer with non-negligible rate. The corrosion rate of Fe is considerably reduced by the Y addition, but the alloy corrodes still much more rapidly than Y. The sulphidation kinetics is generally rather irregular for both the pure metals, while the corrosion rate of the alloy decreases with time and tends to become parabolic after an initial period of 12 similar to 17 h. The sulphidation behaviour of the alloys is discussed by taking into account the presence of an intermetallic compound Fe17Y2 and the limited solubility of Y in Fe.

关键词: high-temperature sulfidation;most-reactive component;ni-nb alloys;h2-h2s mixtures;behavior;600-degrees-c-800-degrees-c;oxidation

Correlation between the surface state and optical properties of S(6) site and C(2) site in nanocrystalline Eu(3+):Y(2)O(3)

Journal of Alloys and Compounds

Eu(3+) doped Y(2)O(3) nanocrystals are synthesized via precipitation and hydrothermal methods. With the increase of hydrothermal temperature, the number of surface states decreases when nanorods are formed. The decrease of surface states induces the increase in the ratio of S(6) site to C(2) site, and meanwhile results in the spectral red-shift of charge transfer band as well as the enhancement of red emission. The results indicate that the surface states and optical properties have close correlations. (C) 2010 Elsevier By. All rights reserved.

关键词: Luminescence;Hydrothermal method;Nanocrystals;Optical properties;luminescence properties;hydrothermal synthesis;size;eu3+;y2o3;photoluminescence;nanopowders;symmetry;ceramics;phosphor

结构钢S355N及S355N-Z25的低温CTOD断裂韧性及其da/dN研究

陈立志 , 张亚军

材料开发与应用 doi:10.3969/j.issn.1003-1545.2011.05.010

分别采用三点弯曲SE(B)与紧凑拉伸C(T)试样,通过-20℃的低温裂纹尖端张开位移CTOD断裂韧性试验及疲劳裂纹扩展速率da/dN试验,研究了S355N及S355N-Z25结构钢的裂纹启裂与扩展的抗力.研究结果表明:S355N钢抵抗裂纹启裂及前期扩展的能力比S355N-Z25钢强,但前者抵抗裂纹后期扩展的能力比后者弱；当应力强度因子范围,△K小于34.3MPa·√m时,S355N钢的疲劳抗力比S355N-Z25钢弱,当△K等于34.3MPa·√m时,两者具有相同的疲劳抗力,当△K大于34.3MPa·√m时,前者的疲劳抗力比后者强.研究结果对两种钢板在工程上应用及结构的安全评定提供了参考.

关键词: S355N及S355N-Z25钢板 , 低温CTOD断裂韧性 , 疲劳裂纹扩展速率da/dN , 裂纹启裂 , 裂纹扩展 , 抗力