C. Y. Ban
,
J.Z. Cui
,
Q.X. Ba
金属学报(英文版)
The structures and macro-segregation of 2124 Al-alloy were studied when a pulsedmagnetic field (PMF) was applied during solidification. It is found through experi-ments that a remarkable change occurs in the solidification structures of 2124 Al-alloyunder pulsed magnetic field. The eutectic phase at grain boundaries change from thickcontinuous eutectic network to thin discontinuous one, and the distribution of soluteelements was also homogenized. The typical negative segregation phenomenon of Cu incommon solidification condition was restrained, and the segregation of Mg decreased.
关键词:
aluminium alloy
,
null
,
null
,
null
材料科学技术（英）
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
Oxidation of Metals
The corrosion of Co-15 wt.% Y has been studied at 600-800 degrees C in H-2-H2S-CO2 mixtures providing a sulfur pressure of 10(-8) atm at 600-800 degrees C and of 10(-7)atm at 800 degrees C and an oxygen pressure of 10(-24)atm at 600 degrees C and of 10(-20)atm at 700-800 degrees C. The corrosion rates in such sulfidizing-oxidizing atmospheres were compared,,with those of pure cobalt and yttrium. The addition of yttrium to cobalt is only slightly beneficial, since Soi a yttrium content of 15 wt.% the corrosion rate is reduced quite significantly with respect to pure cobalt at 800 degrees C under 10(-7)atm S-2, only to a limited extent at 600 degrees C, and even slightly increased at 700 degrees C. Moreover, the alloy corrodes considerably more rapidly than pure yttrium at 800 degrees C, when the latter. behaves protectively.,At 600 and 700 degrees C, yttrium exhibited breakaway behavior, while the alloy corroded more rapidly than yttrium at short times, but more slowly at long times. Under all conditions, except at 800 degrees C under 10(-8) atm? Sr, the alloy forms ail external layer of cobalt sulfide overlying an intermediate region of very complex composition containing a mixture of the compounds of the two metals and ail innermost region of internal attack containing compounds of yttrium with both oxygen and sulfur. Thus, cobalt can still diffuse through the intermediate region to form the outer cobalt-sulfide layer at nonnegligible rates. The scaling behavior of rite Co-15% Y alloy is discussed by taking into account the limited solubility of yttrium in cobalt as well as the presence of an intermetallic Co-Y compound in the alloy.
关键词:
cobalt;yttrium;two-phase alloys;sulfidation;oxidation;high-temperature sulfidation;2-phase binary-alloys;most-reactive;component;ni-nb alloys;internal oxidation;oxidant pressures;h2-h2s;mixtures;co;behavior;600-degrees-c-800-degrees-c
Corrosion Science
The corrosion of pure yttrium and of a cobalt alloy containing approximately 15 wt% yttrium was studied at 600-800 degrees C in H-2-CO2 mixtures providing an equilibrium oxygen pressure of 10(-24) atm at 600 degrees C and 10(-20) atm at 700 and 800 degrees C. The corrosion of yttrium under these low oxygen pressures resulted in the growth of Y2O3 scales which was rather protective at 800 degrees C, presenting two approximately parabolic stages with a smaller rate Constant at longer times, but non-protective and faster at lower temperature. The oxidation of Co-15Y was rather irregular under all conditions, but generally slow: in particular, at 800 degrees C the rate decreased almost to zero after about 17 h oxidation. The oxidation of this alloy produced a thin external layer of pure cobalt metal overlying a region of internal oxidation, where the Y-rich phase was transformed into a mixture of cobalt metal and yttrium oxide. The microstructure of the internal oxidation region followed closely that of the original alloy, while no yttrium depletion was observed beneath the front of internal oxidation. These results are examined by taking into account the low solubility of Y in Co and the existence of an intermetallic compound in the alloy. (C) 1997 Elsevier Science Ltd.
关键词:
cobalt;yttrium;alloys;internal oxidation;2-phase binary-alloys;high-temperature oxidation;most-reactive;component;possible scaling modes;low oxidant pressures;internal;oxidation;a/o al;corrosion;1173-k
Oxidation of Metals
The corrosion of pure yttrium and of two Fe-base alloys containing approximately 15 and 30 wt.% Y was studied at 600-800 degrees C in H-2-CO2 mixtures providing an equilibrium oxygen pressure of 10(-24) atm 600 degrees C and 10(-20) atm at 700 and 800 degrees C. The corrosion of yttrium under these low oxygen pressures resulted in the growth of Y2O3 scales and presented two approximately parabolic stages at 800 degrees C, while at 600-700 degrees C it was faster and nonprotective. The corrosion of the two alloys followed approximately the parabolic rare law, except for Fe-15Y at 600 degrees C which oxidized nearly linearly. At 600 and 700 degrees C, when the gas-phase oxygen pressure was in the field of stability of iron oxide, the alloys formed also a thin external Fe3O4 layer, while at 800 degrees C, when the oxygen pressure was below the stability of FeO, a thin outermost layer of pure iron was observed to form. Under all conditions a region of internal oxidation formed in the alloy, in which the yttrium-rich phases were transformed into a mixture of iron metal and oxides, which included double Fe-Y oxides as well as Y2O3. The microstructure of the internal-oxidation region followed closely that of the original alloys, which moreover did not undergo any yttrium depletion. These results are examined by taking into account the low solubility of yttrium ib iron and the presence of intermetallic compounds in the alloys.
关键词:
iron;yttrium;alloys;internal oxidation;2-phase binary-alloys;high-temperature oxidation;most-reactive;component;possible scaling modes;low oxidant pressures;internal;oxidation;al alloys;a/o al;corrosion;1173-k
Corrosion Science
The corrosion of two iron-based alloys containing 15 and 30 wt% yttrium and of pure yttrium has been studied at 600-800 degrees C in H-2-H2S-CO2 mixtures under a sulfur pressure of 10(-8) atm and an oxygen pressure of 10(-24) atm at 600 degrees C and of 10(-20) atm at 700-800 degrees C to establish the effect of yttrium additions on the resistance of pure iron to mixed sulfidizing-oxidizing atmospheres of high sulfur potential. The presence of yttrium is only slightly beneficial, since even a yttrium content of 30 wt% can only reduce the corrosion rate of iron to a limited extent at 600 and 800 degrees C, but not at 700 degrees C. More precisely, at 600 and 700 degrees C, when yttrium shows breakaway, the alloys corrode more rapidly than pure yttrium at short times, but presumably more slowly at long times. On the contrary, at 800 degrees C, when yttrium behaves protectively, the two alloys corrode considerably more rapidly than pure yttrium. Under all conditions the two alloys form an external FeS layer overlying a very complex intermediate region containing a mixture of the compounds of the two metals and an innermost zone of internal attack containing compounds of yttrium with both oxygen and sulfur, Thus, iron can still diffuse through the intermediate region at nonnegligible rates to form the outer FeS layer. The scaling behavior of these alloys is discussed by taking into account the limited solubility of yttrium in iron as well as the presence of intermetallic Fe-Y compounds. (C) 1999 Elsevier Science Ltd. All rights reserved.
关键词:
iron;yttrium;alloys;sulfidation;oxidation;high-temperature sulfidation;2-phase binary-alloys;fe-nb alloys;most-reactive component;internal oxidation;oxidant pressures;h2-h2s;mixtures;behavior;ni;600-degrees-c-800-degrees-c
Physics Letters A
The magnetic properties of the mixed ferro-ferrimagnetic compounds with (A(a)B(b)C(c))(y)D, in which A, B, C and D are four different magnetic ions and form four different sublattices, are studied by using the Ising model. And the Ising model was dealt with standard mean-field approximation. The regions of concentration in which two compensation points or one compensation point exit are given in c-a, b-c and a-b planes. The phase diagrams of the transition temperature T-c and compensation temperature T-comp are obtained. The temperature dependences of the magnetization are also investigated. Some of the result can be used to explain the experimental work of the molecule-based ferro-ferrimagnet ((NiaMnbFecII)-Mn-II-Fe-II)(1.5) [Cr-III (CN)6] - zH(2)O. (C) 2003 Elsevier B.V. All rights reserved.
关键词:
mixed ferro-ferrimagnet;Ising model;four sublattices;phase diagram;transition temperature;compensation temperature;magnetic-properties;prussian blue;alloy
Corrosion Science
The oxidation of pure Co and two Co-Y alloys containing 2 at.% and 5 at.% Y has been studied at 600-800 degrees C in air. The oxidation of pure cobalt at all temperatures followed the parabolic rate law. The oxidation of the two alloys approximately followed the parabolic rate law at 800 degrees C, but was closer to cubic behavior at 600 and 700 degrees C except Co-5Y at 600 degrees C, which deviated from the cubic and parabolic rate law. The corrosion of both alloys at the three temperatures produced an external scale containing Co oxides (Co3O4, CoO) and Y2O3 and an internal oxidation region where Co17Y2 was converted into Co and Y2O3. The distribution of Y2O3 closely followed that of the intermetallic compound (Co17Y2) in the original alloy. The corrosion mechanism of the alloys is examined. (C) 1999 Elsevier Science Ltd. All rights reserved.
关键词:
Co;Y;oxidation;high-temperature oxidation;possible scaling modes;internal oxidation;oxidant pressures;h-2-h2s mixtures;sulfidation;oxygen
Oxidation of Metals
The oxidation of Fe- Y alloys containing 2 and 5 at.% Y and pure iron has been studied at 600-800 degrees C in air. The oxidation of pure iron follows the parabolic rate law at all temperatures. The oxidation of Fe-Y alloys at 600 degrees C approximately follows the parabolic rate law, but not at 700 and 800 degrees C, where the oxidation goes through several stages with quite different rates. The oxide scales on Fe-2Y and Fe-5 Y at 700 and 800 degrees C are composed of external pure Fe oxides containing Fe2O3, Fe3O4, and FeO, with FeO being the main oxide and an inner mixture of FeO and YFeO3. The scales on Fe-2Y and Fe-5Y at 600 degrees C consist of Fe2O3, Fe3O4, and Y2O3, with a minor amount of FeO. Significant internal oxidation in both Fe-Y alloys occurred at all temperatures. The Y-containing oxides follow the distribution of the original intermetallic compound phase in the alloys. The effects of Y on the oxidation of pure Fe are discussed.
关键词:
pure Fe;Fe-Y alloys;oxidation;high-temperature oxidation;possible scaling modes;2-phase;binary-alloys;low-oxygen pressures;oxidant pressures
Transactions of Nonferrous Metals Society of China
The influence of Zr and Y on the cast microstructure of a nickel-based superalloy was investigated by optical microscopy (OM), scanning electron microscopy(SEM), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD). The gamma+gamma' eutectic volume in the superalloy rises notably with the increase of Zr or Y content. Meanwhile, the morphologies of primary MC carbides change from needle and platelet-like to blocky shape with increasing Zr and Y doped. The XRD results show that the primary MC carbide lattice constant increases with Zr and Y additions, and EPMA investigation shows that the platelet-like MC carbides contain primarily Nb and C, while those carbides in blocky shape have 39.2% Zr and 39.6% Nb in average,. These influences on the cast microstructure can be attributed to the atomic size effects of Zr and Y.
关键词:
yttrium;zirconium;carbides;nickel based superalloys;microstructure;solidification;carbide morphology;mechanical-properties;boron;ni3al;yttrium;sulfur
