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ABSTRACT: A continuous graphite fibre reinforced aluminium matrix composite (Grf/Al) with 60 vol.-% Grf content was produced by squeeze casting technology. The composite was dense and macroscopically homogeneous, and only a small amount of aluminium carbide was found in the Gr/Al interface. Tensile and bending strengths of Grf/Al composites have been measured in the temperature range between −40 and 100°C. With increasing tested temperatures, the tensile and bending strengths of Grf/Al composites were enhanced from 891 to 1095 MPa and from 967 to 1234 MPa respectively. The temperature dependence mechanisms of composite strength were analysed in terms of changing of residual stress and mechanical properties of matrix respectively.
Materials Science and Technology 01/2010; 26(2):184-187. · 0.77 Impact Factor
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ABSTRACT: Grains, grain boundaries, magnetic domain distributions, and their correlations in Fe <sub>81</sub> Ga <sub>19</sub> alloys as-cast, annealed, and under compressive and grinding stresses were investigated using scanning electron acoustic microscopy (SEAM) and magnetic force microscopy (MFM). For as-cast and annealed samples, the main domain structure obtained using SEAM is not clear. For samples under stresses, the main domains are obvious and regular. For the sample under compressive stress, its stripe domains array orderly and perpendicularly to the stress direction. The subdomains of as-cast sample observed using MFM show a clear dendritic structure. However, for the sample under compressive stress, the subdomains are irregular. These results may be helpful to understand the magnetostrictive behavior of Fe–Ga alloys under stress.
Journal of Applied Physics 02/2009; · 2.17 Impact Factor
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Journal of Applied Physics. 01/2009; 105(1):013913.
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ABSTRACT: The novel ferromagnetic shape memory alloy Mn50Ni28Ga22 exhibits a single martensite phase with tetragonal structure at room temperature. Its martensite structure was investigated
by scanning electron acoustic microscopy. Stripe twin variants exist in every grain and exhibit the configurations of the
typical self-accommodation arrangement. The interfaces between twin variants are straight and clear. However, the magnetic
domain walls obtained by the Bitter method coincide well with the twin variant boundaries. The first direct evidence of the
coincidence between micron-scale magnetic domains and martensite variants is presented. These results will be beneficial for
the development of ferromagnetic shape memory alloys and for the understanding of the correlation between magnetic domains
and crystallographic twin variant domains as well.
Applied Physics A 07/2008; 92(2):309-311. · 1.63 Impact Factor
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ABSTRACT: The paper reports on the effect of substituting Mn for Fe on the magnetostrictive and related properties of Fe81−xMnxGa19 alloys. Samples of composition were prepared in polycrystalline form and were all single phase BCC. It is shown that the magnetostriction observed in Fe81Ga19 can be enhanced up to about 11% by Mn substitution with a maximum effect at x = 8. The change in the magnetostrictive coefficient of Fe81Ga19 with Mn substitution is accompanied by a monotonic increase in resistivity, being increased by almost a factor of 2 for x = 8. We also found that the lattice parameter of the alloys increased with the increase in Mn concentration and the Curie temperature decreased monotonically at the same substitution.
Journal of Physics D Applied Physics 12/2007; 41(1):015002. · 2.54 Impact Factor
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ABSTRACT: The structure and magnetic properties of Gd3(Fe1−xCox)28Nb compounds, with x ranging from 0 to 0.4, have been investigated by means of x-ray diffraction and magnetic measurement. All compounds investigated crystallize in the Nd3(Fe, Ti)29-type structure. The lattice parameters and the unit-cell volume decrease with increasing Co content x. It is found that substitution of Co for Fe leads to a significant increase in the Curie temperature from 503 K for x = 0 to 920 K for x = 0.4. Saturation magnetization gradually increases with increasing Co. All compounds show easy plane-type anisotropy. The anisotropy field Ba at 5 K obviously decreases with increasing Co content.
Journal of Physics D Applied Physics 08/2005; 38(16):2755. · 2.54 Impact Factor
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ABSTRACT: Microstructural aspects and interfacial characteristics of deformed martensite variants in a compressed Ni55Mn20Ga25 (at.-%) alloy have been investigated using transmission electron microscopy. It is shown that the undeformed specimen exhibits a well accommodated morphology and a straight and well defined interfacial boundary. After deformation, reorientation of martensite variants occurs at the expense of unfavourable martensite variants, and the interfacial boundary changes from sharp and straight to curved and irregular. Meanwhile, lattice defects are formed inside the variants even in slightly compressed samples. With increasing deformation, high density lattice defects are generated and rearranged inside the variants as well as in the interfacial boundaries between variants.
Materials Science and Technology 10/2003; 19(11):1622-1625. · 0.77 Impact Factor
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Journal of Materials Science Letters 08/2003; 22(18):1241-1242.
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ABSTRACT: The Ho-substituted ( Nd <sub>1-x</sub> Ho <sub>x</sub>)<sub>3</sub> Fe <sub>23-y</sub> Co <sub>6</sub> V <sub>y</sub> compounds with x=0–0.9 have been synthesized and their structure and intrinsic magnetic properties have been investigated by x-ray diffraction and magnetic measurements. It is found that all the investigated compounds crystallize in the Nd <sub>3</sub>( Fe,Ti )<sub>29</sub> -type structure with monoclinic symmetry and A<sub>2/m</sub> space group. The unit-cell volume V shows a decreasing tendency with increasing Ho content, reflecting the lanthanum contraction. All the compounds show easy-plan type anisotropy at room temperature. The Curie temperatures T<sub>c</sub> are almost independent of the Ho content and the spin reorientation temperature, T<sub> sr </sub>, decreases with increasing Ho content from 266 K for x=0 to 127 K for x=0.7. No spin reorientation occurs for x=0.9. The saturation magnetization M<sub>s</sub> decreases linearly with increasing Ho content due to the antiferromagnetic coupling between Ho and Nd moments. The anisotropy field B<sub>a</sub> increases first, going through a maximum at x=0.5, y=2.0, and then decreases with increasing Ho content. © 2003 American Institute of Physics.
Journal of Applied Physics 06/2003; · 2.17 Impact Factor
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ABSTRACT: We have obtained single-phase compounds Gd <sub>3</sub> Fe <sub>29-x-y</sub> Co <sub>x</sub> Cr <sub>y</sub> with the Nd <sub>3</sub> ( Fe,Ti )<sub>29</sub> -type. Cr is a stabilizing element and also increases the solid-solution limit of Co in the Gd <sub>3</sub> Fe <sub>29-x-y</sub> Co <sub>x</sub> Cr <sub>y</sub> compounds. Substitution of Co by Fe results in a significant change of the magnetocrystalline anisotropy and changes the easy magnetization direction from basal-plane to easy-axis when x≫10 and y=4. The intensity of the magnetic interactions in Co-rich Gd <sub>3</sub> Fe <sub>29-x-y</sub> Co <sub>x</sub> Cr <sub>y</sub> compounds has been calculated from the high-field magnetization measurements. The Co substitution suppresses the Invar anomaly found in the Gd <sub>3</sub>( FeCr )<sub>29</sub> compounds. © 2003 American Institute of Physics.
Journal of Applied Physics 06/2003; · 2.17 Impact Factor
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ABSTRACT: The effect of annealing treatment and thermal cycling on the phase transformation behaviour of Ni-Mn-Ga alloy prepared by arc melting technology has been investigated. The results show that the main transformation parameters decrease in a few initial thermal cycles, and then stabilise with further cycling. The transformation temperature interval decreases with an increase of annealing temperature. As cast material exhibits a columnar grain microstructure, while annealed material exhibits coarsened grains with clearly martensitic plates. When the alloy is annealed at 1073 K, both the martensite start temperature M
s and the austenite finish temperature A
f decrease, while the martensite finish temperature M
f and the austenite start temperature A
s increase with an increase in annealing time. This implies that the chemical order degree of the parent phase increases with increasing annealing time, which causes the chemical driving force for martensitic transformation to decrease.
Materials Science and Technology 05/2003; 19(6):691-694. · 0.77 Impact Factor
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ABSTRACT: Formation of Ce3Fe29−x−yCoxMoy(x=0,3,6,10) compounds has been investigated by means of x-ray diffraction and magnetic measurements. It is found that the required Mo content to stabilize the 3:29 compounds decreases monotonically as Co content increases, totally different from the discovery in the Gd3(Fe1−xCox)29−yCry compounds. Meanwhile, we adopted a lattice inversion method in acquiring the interatomic potentials to rare-earth-transition metal intermetallic compounds, and investigated the substitution behaviors of Mo, Cr, V, and Mn in Fe-based and Co-based 3:29 compounds, respectively, by combining these potentials with computer simulation. The calculated results show that the required Mo content in R3Co29−xMox compounds is lower than that in R3Fe29−xMox compounds, whereas the Cr content in R3Co29−xCrx compounds higher than that in R3Fe29−xCrx compounds, coinciding well with the previous discovery and the experimental results in this work. © 2003 American Institute of Physics.
Journal of Applied Physics 05/2003; 93(10):6921-6923. · 2.17 Impact Factor
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ABSTRACT: The magnetic properties of TbFe12-xTix single crystals with x=0.8–1.4 have been investigated in detail using ac and dc susceptibility and high-field magnetization measurements. A first-order spin reorientation transition from a basal plane easy magnetization direction at low temperatures to an axial easy magnetization direction at high temperatures occurs for all the investigated compounds. The spin reorientation temperatures have been determined by combining ac and dc susceptibility measurements and its dependence on both the Ti content and the applied magnetic field has been studied. A first-order magnetization process is observed below a certain temperature when the magnetic field is applied along the [001] crystallographic direction. The dependence of the transition critical field on the Ti content has been analyzed. The magnetic behavior has been interpreted using a two-sublattices model for the magnetic structure, in the frame of a crystal-electric-field–mean-field model. The parameters describing the crystal-field interaction in TbFe12-xTix compounds have been determined. The calculated magnetic behavior shows a good agreement with experimental results in a wide temperature range.
Phys. Rev. B. 01/2003; 67(1).
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ABSTRACT: The structure and magnetic properties of the (Nd1−xErx)3Fe18Co6Cr5 compounds with x = 0.0–0.8 have been investigated by means of x-ray diffraction and magnetic measurements. It is found that all the compounds are single phase and crystallize in the Nd3(Fe,Ti)29-type structure with monoclinic symmetry and space group A2/m. The lattice constants a, b and c and the unit-cell volume V show a tendency to decrease with increasing Er content, reflecting the lanthanide contraction. The Curie temperature decreases with increasing Er content. The spin-reorientation temperature Tsr increases with increasing Er content till x = 0.2, then tends to saturate upon further increase in Er content. The saturation magnetization at 5 K decreases with increasing Er content owing to the antiferromagnetic coupling between Er and Nd moments. A first-order magnetization process is observed for compounds with x = 0, 0.2 and 0.4 at critical field values of 8 T, 4.5 T and 3.5 T, respectively, applied along the hard magnetization direction.
Journal of Physics D Applied Physics 11/2002; 35(24):3161. · 2.54 Impact Factor
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Z. H. Liu,
M. Zhang,
W. Q. Wang,
W. H. Wang,
J. L. Chen, G. H. Wu,
F. B. Meng,
H. Y. Liu,
B. D. Liu,
J. P. Qu,
Y. X. Li
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ABSTRACT: Quaternary Heusler alloy Ni2(Mn,Fe)Ga has been studied systematically for the structure, martensitic transformation, and magnetic properties in two systems of Ni50.5Mn25−xFexGa24.5 and Ni50.4Mn28−xFexGa21.6. Substituting Fe for Mn up to about 70%, the pure L21 phase and the thermoelastic martensitic transformation still can be observed in these quaternary systems. Iron doping dropped the martensitic transformation temperature from 220 to 140 K, increased the Curie temperature from 351 to 429 K, and broadened the thermal hysteresis from about 7 to 18 K. Magnetic analysis revealed that Fe atoms contribute to the net magnetization of the material with a moment lower than that of Mn. The temperature dependence of magnetic-field-induced strains has been improved by this doping method. © 2002 American Institute of Physics.
Journal of Applied Physics 10/2002; 92(9):5006-5010. · 2.17 Impact Factor
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ABSTRACT: The effects of Mn substitution on the magnetic properties of Er2Fe17−xMnx compounds have been investigated by different experimental techniques. An unusual composition dependence of the unit cell volume at room temperature occurs due to a strong magnetovolume effect, which has been confirmed by high temperature linear thermal expansion measurements. From magnetization measurements the composition dependence of the spontaneous magnetization of the 3d-sublattice magnetic moment and of the Curie temperature has been determined. Spin reorientation has been detected for compounds with 3⩽x⩽5.5, as well as remarkable magnetic history effects. © 2002 American Institute of Physics.
Journal of Applied Physics 07/2002; 92(3):1453-1457. · 2.17 Impact Factor
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ABSTRACT: LaFe13−xSix compounds with x=2.4, 2.6, and 2.8 have been carefully prepared and characterized. X-ray powder diffraction patterns confirm that the samples crystallize in a single NaZn13-type phase. Magnetic measurements were carried out in a SQUID magnetometer. The Curie temperature Tc of LaFe13−xSix samples decreases nearly 50 K with x increasing from 2.4 to 2.8. Around Tc the samples exhibit a typical second-order phase transition; and no trace of first-order itinerant electron metamagnetic transition is found. So it is reliable to characterize the magnetic entropy change around Tc using magnetic measurement. The maximum values of the magnetic entropy change of LaFe13−xSix samples are found to be, at their Curie temperatures, 5.85, 5.9, and 3.7 J/kg.K for x=2.4, 2.6, and 2.8 under a field change of 5 T (0–5 T). For the quite large magnetic entropy change over a wide temperature range, LaFe13−xSix compounds appear, therefore, to be a potential material candidate for magnetic cooling. © 2002 American Institute of Physics.
Journal of Applied Physics 05/2002; 91(10):8537-8539. · 2.17 Impact Factor
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ABSTRACT: Thermal expansion and magnetic properties of the YFe11−xCoxTi compounds have been investigated by various experimental methods. A large magnetovolume effect has been clearly observed below TC for the Fe-rich compounds. When the transition metal concentration changes from Fe to Co rich, the invar-like effect becomes less pronounced and almost disappears close to the pure-Co compound. The dependence of the spontaneous volume magnetostriction on temperature and Co concentration has been estimated from the thermal expansion measurements. It has been found that, for the YFe11−xCoxTi compounds, the largest spontaneous volume magnetostriction (about 2.1%) occurs at x=3, close to the concentration in which a maximum in saturation magnetization was found. The anomalous thermal expansion can be attributed to the volume dependence of the magnetic energy, which is very sensitive to the distance between first-neighbors transition-metal atoms for Fe-rich compounds. © 2002 American Institute of Physics.
Journal of Applied Physics 05/2002; 91(10):8216-8218. · 2.17 Impact Factor
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ABSTRACT: The magnetic properties of RFe <sub>12-x</sub> Nb <sub>x</sub> and R(Fe <sub>1-y</sub> Co <sub>y</sub>)<sub>11.3</sub> Nb <sub>0.7</sub> compounds with R=Y, Tb, and Dy have been investigated in the concentration region defined by 0.6≪x≪0.8 and y≤0.3, where the compounds are single phase with the ThMn <sub>12</sub> -type of structure. The Curie temperature T<sub>C</sub> of the RFe <sub>12-x</sub> Nb <sub>x</sub> compounds is almost independent of the Nb content whereas the saturation magnetization M<sub>s</sub> decreases with increasing Nb content. The spin-reorientation temperature T<sub> sr </sub> of the TbFe <sub>12-x</sub> Nb <sub>x</sub> and DyFe <sub>12-x</sub> Nb <sub>x</sub> compounds decreases monotonically with increasing x. Substitution of Co for Fe in RFe <sub> 11.3 </sub> Nb <sub>0.7</sub> leads to a remarkable increase of T<sub>C</sub> and the appearance of a maximum in the Co-concentration dependence of M<sub>s</sub>. In contrast, T<sub> sr </sub> decreases monotonically with increasing Co content for both R=Tb and Dy. The modification of T- and R-sublattice anisotropy originating from a change of the Nb content and from substitution of Co for Fe was analyzed by combining crystalline electric field theory and the individual-site model. © 2002 American Institute of Physics.
Journal of Applied Physics 03/2002; · 2.17 Impact Factor
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ABSTRACT: Single crystals of a pseudoquaternary Heusler alloy, Ni <sub>52</sub> Mn <sub>16</sub> Fe <sub>8</sub> Ga <sub>24</sub>, have now been synthesized. The substitution of Fe for Mn strengthens the magnetic exchange interactions, increasing the Curie temperature to 381 K. The Fe also increases the Ni magnetic moment to 0.41 μB relative to that in the stoichiometric Heusler composition. The strain accompanying the martensitic transformation is 2.4% in zero field and can be enhanced to 4.2% by a field of 1.2 T. A field-induced strain of 1.15% has been induced along [001] in unstressed crystals with magnetic fields of 1.2 T applied at 291 K. © 2002 American Institute of Physics.
Applied Physics Letters 02/2002; · 3.84 Impact Factor
