Y.G. Cao
,
X.Y. Sun
金属学报(英文版)
J-integral and crack opening displacement δ(COD) were important parameters for characterization of fractures in engineering materials. The relationship between J-integral and COD has been investigated for a long time and was enerally represented as J = m σyδ, where σy is the yield strength and m is a function of specimen geometry and material properties. To determine the value of m, extensive studies and experiments have been performed. The method that used the fracture-surface topography analysis (FRASTA) for determining J-integral from fracture surfaces of materials was introduced. On the basis of the relationship between COD and fracture surface average profile, the relationship between J-integral and COD was deduced and compared with the generally used equation. The method was experimentally confirmed to be able to provide a new way to determine the relationship between J-integral and COD.
关键词:
FRASTA
,
null
,
null
Applied Physics Letters
The effect of nonmagnetic Y partial substitution at the Dy site in Dy(1-x)Y(x)MnO(3) up to x=0.2 on magnetism, specific heat, and ferroelectricity is investigated, which resulted in a preliminary multiferroic phase diagram. It is revealed that the Y partial substitution suppresses the Dy-spin ordering point (T(Dy)) and ferroelectric ordering point (T(FE)) but enhances the Mn-spin ordering point (T(N)). The interaction between the spins of Dy and Mn is remarkably affected by Y substitution. The measured electrical polarization depends on the Y substitution in a complex way because the ferroelectricity is sensitive to the interaction between the spins of Dy and Mn. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3536506]
关键词:
ferroelectricity;polarization
材料科学技术（英文）
The glass-forming ability (GFA) of Nd(70-x)Fe(20)Al(10)Y(x) and Nd(60-x)Fe30Al(10)Y(x) (0 less than or equal to x less than or equal to15) alloys produced by Cu mold casting was investigated. Except Y = 5 at. pct, bulk amorphous Nd(70-x)Fe(20)Al(10)Y(x) alloys up to 2 mm in diameter were obtained. The GFA for Nd(60-x)Fe(30)Al(10)Y(x) alloys, however, was found to decrease with increase of Y due to the increasing compositional deviation from the original eutectic point of Nd(60)Fe(30)Al(10) alloy. The Nd(60)Fe(20)Al(10)Y(10) and Nd(60)Fe(30)Al(10) alloy exhibit the largest GFA and can be cast into bulk amorphous cylindrical specimens of 3 mm in diameter. The melting temperature or/and the reduced crystallization temperature is closely related to the GFA of Y-containing alloys. The bulk amorphous cylinder for the Nd(55)Fe(20)Al(10)Y(15) alloy shows a distinct glass transition temperature and a wide supercooled liquid region before crystallization. The crystallization temperature, T(g), and the supercooled liquid region, DeltaT(x), are 776 K and 58 K, respectively, The GFA and thermal stability of the Nd-Fe-Al-Y alloys were discussed.
关键词:
Nd-based alloys;glass forming ability;liquidus temperature;thermal;stability;supercooled liquid region;bulk amorphous-alloys;metallic glasses;transition temperature;thermal-stability;atomic size;ni alloys;cu;alloys;diameter;tm
Physica B-Condensed Matter
The magnetic properties and magnetocaloric effect of Tb(1-x)Y(x)CoC(2) (x = 0, 0.1, 0.2, 0.3, 0.4) compounds have been investigated systematically. All the compounds undergo second-order transitions from paramagnetic to ferromagnetic states without thermal and magnetic hysteresis. With increasing Y content from 0 to 0.4, the Curie temperatures decrease nearly linearly from 28 to 18 K. The nature of the second-order phase transitions can be confirmed by Arrott plots. For Tb(0.6)Y(0.4)CoC(2) compound, the maximum value of the magnetic entropy change -Delta S(M) at 20 K is 9.35 J kg(-1) K(-1) for an external field change of 5T (5.14 J kg(-1) K(-1) for 2T). The large reversible magnetic entropy change makes Tb(0.6)Y(04)CoC(2) compound an attractive candidate for the application at hydrogen liquefaction temperature. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Curie temperature;Magnetocaloric effect;Magnetic properties;ac susceptibility
Materials Letters
The dynamic hysteresis in a planar X-Y model as a function of frequency and amplitude of external field, at a temperature far below its Curie point, is studied by means of Monte Carlo (MC) method. The evolution of hysteresis dispersion is simulated in details and the earlier proposed scaling on the hysteresis dispersion is confirmed in the present system. It is predicted that the unique characteristic time for domain reversal is inversely proportional to the field amplitude once the amplitude is not very small. (C) 2002 Elsevier Science B.V. All rights reserved.
关键词:
dynamic hysteresis;scaling;planar X-Y model;kinetic ising-model;magnetic hysteresis;phase-transition;films
Journal of Physical Chemistry C
We report the electrical, thermal, magnetic, and thermoelectric properties of Y-doped Ca(3)Co(4)O(9) from 300 down to 5 K. The results indicate that with Y doping, the increase of resistivity originates from the decreases of carrier concentration and mobility, while the increase of Seebeck coefficient is caused by the reduction of carrier concentration together with the enhanced electronic correlation. Point-defect scattering, is the dominant thermal transport mechanism in this system. Due to the considerable difference in mass between Y(3+) and Ca(2+), thermal conductivity is observably suppressed by doping. The substitution of Y also disturbs the interlayer ferrimagnetic coupling. The ground state of this System converts front ferrimagnetism to paramagnetism gradually. The alteration of transport properties of Ca(3-x)Y(x)Co(4)O(9) reveals two Crossovers: the transition from Fermi-liquid-like metal to thermally activated semiconductor occuring at x approximate to 0.25, and the transition from thermally activated semiconductor to two-dimensional variable range hopping semiconductor occurring at x approximate to 0.5. The optimal thermoelectric response In Ca(3-x)Y(x)Co(4)O(9) is found to exist only at the critical state after which the doping-induced metal-insulator transition takes place. Oil the basis of these experimental results, a possible phase diagram for Ca(3-x)Y(x)Co(4)O(9) is proposed.
关键词:
temperature thermoelectric properties;giant magnetoresistance;solid-solutions;conductivity;electron;system;ca3co4o9+delta;thermopower;crystals;behavior
Ieee Transactions on Magnetics
The spin orientation and spontaneous magnetostriction of multicomponent TbxDy1-x-yPry(Fe0.9B0.1)(1.93) (0.10 less than or equal to x less than or equal to 0.25, 0.30 less than or equal to y less than or equal to 0.60) Laves phases were studied by step-scanning their (440) X-ray diffraction lines. The easy magnetization direction (EMD) of the Laves phases changed from the (100) to (111) axis when x was increased from 0.10 to 0.25. With increasing y, the EMD of Tb0.15Dy0.85-yPry(Fe0.9B0.1)(1.93) and Tb0.2Dy0.8-yPry(Fe0.9B0.1)(1.93) Laves phases reoriented from the (100) to (111) axis. The magnetostriction coefficient lambda(111) of TbxDy1-x-yPry(Fe0.9B0.1)(1.93) Laves phases increased with increasing x (or y) when y (or x) was kept constant.
关键词:
Laves phases;magnetostriction;spin orientation;X-ray diffraction;anisotropy compensation;alloys
Acta Materialia
The glass-forming ability (GFA) and thermal stability of Nd(70-x)Fe(20)Al(10)Y(x) (0less than or equal toxless than or equal to15) alloys produced by melt spinning and copper-mold casting have been investigated. Ribbon samples in the composition range show a fully amorphous structure. Except Y=5 at.%, bulk amorphous alloys at least 2 mm in diameter were obtained. Both the amorphous ribbon and the bulk cylinder for the Nd(55)Fe(20)Al(10)Y(15) alloy show a distinct glass transition temperature and a wide supercooled liquid region before crystallization. It is suggested to use a new parameter to characterize both the GFA and the thermal stability of Nd-Fe-Al-Y alloys, showing that Nd(60)Fe(20)Al(10)Y(10) alloy is the best one both in GFA and thermal stability. The remanence (J(r)), magnetization (J(1500)), and coercivity (H(c)) for the as-cast Nd(70-x)Fe(20)Al(10)Y(x) amorphous cylinders depend strongly on the composition. The enhanced GFA and thermal stability as well as the reduction of magnetic properties are discussed. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
关键词:
glass-forming ability;Nd(70-x)Fe(20)Al(10)Y(x) metallic glasses;magnetic properties;supercooled liquid region;hard magnetic-properties;bulk;amorphous-alloys;transition temperature;metallic glasses;ni alloys;cu alloys;diameter;fe;tm
