共查询到20条相似文献,搜索用时 31 毫秒
1.
A high-energy ball milling technique using the mechanical alloying method has been employed for fabrication of glassy Co100−xTix (25≤x≤67) alloy powders at room temperature. The fabricated glassy alloys in the Co-rich (33≥x) side exhibit good soft magnetic properties. The binary glassy alloys for which the glass transition temperatures (Tg) have rather high temperatures (above 800 K), show large supercooled liquid regions before crystallization (ΔTx larger than 50 K). The reduced glass transition temperature (ratio between Tg and liquidus temperatures, Tl (Tg/Tl)) was found to be larger than 0.56. We have also performed post-annealing experiments on the mechanically deformed Co/Ti multilayered composite powders. The results show that annealing of the powders at 710 K leads to the formation of a glassy phase (thermally enhanced glass formation reaction), of which the heat of formation was measured directly. The similarity in the crystallization and magnetization behaviors between the two classes of as-annealed and as-mechanically alloyed glassy powders implies the formation of the same glass state. 相似文献
2.
Bulk metallic glasses (BMGs) Fe61Co6Zr8−xHfxMo7B15Al1Y2 (x = 0–8) have been produced by copper mold casting technique using industrial raw materials. The effect of substitution of Hf for Zr on the glass forming ability (GFA) and the magnetic property has been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and superconducting quantum interference device (SQUID). It was found that the substitution of an appropriate amount of Hf for Zr can improve the GFA of the base alloy Fe61Co6Zr8Mo7B15Al1Y2, as demonstrated by the increase in reduced glass transition temperature Trg (=Tg/Tl) and GFA parameters of γ (=Tx/Tg + Tl) and δ (=Tx/Tl − Tg). The Fe61Co6Zr5Hf3Mo7B15Al1Y2 alloy exhibits the highest GFA with the largest Trg (0.612) and δ (1.633), and can cast a fully amorphous rod in 3 mm diameter. The substitution of Hf for Zr also enhances the magnetic properties, as verified by the increase in saturation magnetization (Ms) in the alloy of Fe61Co6Zr3Hf5Mo7B15Al1Y2, whose Ms is approximately 1.5 times higher than that of the base alloy (x = 0) at room temperature. Finally, the effect of the substitution of Hf for Zr on glass forming ability and magnetic properties is discussed. 相似文献
3.
Kaikai Song Xiufang Bian Jing Guo Shenghai Wang Baoan Sun Xuelian Li Caidong Wang 《Journal of Alloys and Compounds》2007,440(1-2):L8-L12
The effects of Ce and Mm contents on the glass forming ability (GFA) of melt-quenched Al89−xNi8CexSi3 and Al89−xNi8MmxSi3 (x = 0, 1, 3, 5, 7 at.%) alloys have been systematically investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). According to the XRD and DSC results, both Ce and Mm elements can enhance the GFA and thermal stability of the Al–Ni–Si alloys. Moreover, only the x = 5 and x = 7 alloys are totally amorphous in both systems quenched at the wheel speed of 36.6 m/s. Compared with amorphous Al84Ni8Ce5Si3 alloy at different cooling rates, amorphous Al84Ni8Mm5Si3 alloy has higher GFA which is considered to have relation to the different atomic structure of the amorphous alloy. 相似文献
4.
J. Vzquez D. García-G. Barreda P.L. Lpez-Alemany P. Villares R. Jimnez-Garay 《Journal of Alloys and Compounds》2005,390(1-2):94-99
The thermal stability and crystallization of alloys in the Ge–Sb–Se system were studied by differential scanning calorimetry (DSC). A comparison of various simple quantitative methods to assess the level of stability of the glassy materials in the above-mentioned system is presented. All of these methods are based on characteristic temperatures, obtained by heating of the samples in non-isothermal regime, such as the glass transition temperature, Tg, the temperature at which crystallization begins, Tin, the temperature corresponding to the maximum crystallization rate, Tp, or the melting temperature, Tm. In this work, a parameter Kr(T) is added to the stability criteria. The thermal stability of some ternary compounds of GexSb0.23−ySe0.77−x+y type has been evaluated experimentally and correlated with the activation energies of crystallization by this kinetic criterion and compared with those evaluated by other criteria. 相似文献
5.
The homogeneity range of U2Co17−xSix system with the hexagonal Th2Ni17-type crystal structure extends from x = 1 to 3.4. The variation of the magnetic properties within the homogeneity range was studied on single crystals. All the compounds are ferromagnetic, Ms and TC decrease monotonously with increasing Si content. The strongly modified magnetic anisotropy of U2Co17−xSix, as compared to isostructural Lu2Co17−xSix with the non-magnetic Lu, points to a magnetic state of U up to x = 3.0. The U contribution to K1 decreases with increasing Si content and vanishes at x = 3.4 that can be treated as a transition from magnetic to non-magnetic state of U. Spin reorientation was observed with varying temperature in compounds with x ≤ 3 due to a competition of the U and Co sublattices anisotropies which occurs as two second-order phase transitions of the “plane–cone” and the “cone–axis” type. 相似文献
6.
Jo Chol-Lyong Xia Lei Ding Ding Dong Yuan-Da Ekoko Gracien 《Journal of Alloys and Compounds》2008,458(1-2):18-21
The structure and magnetic entropy changes in melt-spun and annealed LaFe11.8−xCoxSi1.2 (x = 0, 0.4 and 0.8) ribbons have been investigated. It is found that the value of Tc can be increased continuously up to 290 K for x = 0.8 and the phase transition, at Tc from paramagnetic to ferromagnetic, is changed from first- to second-order due to Co substitution. Large values of the magnetic entropy change are 31 and 13.5 J/kg K in the magnetic field change from 0 to 5 T at 201 K for the LaFe11.8Si1.2 and at 290 K for the LaFe11Co0.8Si1.2 ribbons, respectively. The magnetic entropy change in the LaFe11Co0.8Si1.2 ribbons is higher than that reported in the bulk counterpart and that of conventional MCE materials, such as pure Gd. The enhanced magnetic entropy change of ribbons compared to bulk counterpart is attributed to a more uniform microstructure and element distribution resulting from the high cooling rate by melt-spinning. 相似文献
7.
The HfFe6Ge6-type RMn6Sn6−xXx′ solid solutions (R=Tb, Dy, X′=Ga, In; x≤1.4) have been studied by powder magnetization measurements. All the series are characterized by ferrimagnetic ordering and by a decrease in Curie temperatures with the substitution (ΔTc/Δx≈−39 K for X′=Ga and ΔTc/Δx≈−75 K for X′=In). The RMn6Sn6−xGax systems are characterized by a strong decrease in the spin reorientation temperature with substitution (ΔTt/Δx≈−191 K and −78 K for R=Tb and Dy, respectively) while this transition almost does not change in systems containing indium. The coercive fields drastically decrease with the substitution in the TbMn6Sn6−xGax system while the substitution of In for Sn has a weaker effect. The coercive fields of the Dy compounds do not vary greatly with the substitution in both series. The behaviour of the TbMn6Sn6−xGax is compared with the evolutions observed in the TmMn6Sn6−xGax series. This comparison strongly suggests that the replacement of Sn by Ga changes the sign of the A02 crystal field parameter. 相似文献
8.
J.J. Rieger W.W. Kim G. Fraunberger A. Mielke E.-W. Scheidt G.R. Stewart 《Journal of Alloys and Compounds》1993,200(1-2):59-63
The heat capacity, magnetic susceptibility and magnetization of Y1−xUxRh4B4 were determined within the range from x = 0 to X = 0.65. The influence of the local magnetic moments of the U atoms (dU-U = 5.27 Å) in the CeCo4B4 structure of the tetragonal RERh4B4 was studied. A.c. susceptibility measurements showed a rather large value for the Tc depression of dTc/dx = −1.88 K per at. % U in the lower concentration range x = 0.0 to x = 0.06. In comparison with the (Bardeen-Cooper-Schrieffer) BCS theory and the Abrikosov-Gorkov model for dilute magnetic impurities, the decrease in the jump in specific heat at Tc vs. the depression of Tc is rather strong in these samples, so the existence of a demagnetizing Kondo cloud around the U moments seems likely. In the samples containing more U, the magnetization and d.c. susceptibility showed a tendency towards magnetic behaviour, but no evidence for long-range magnetic order was found. 相似文献
9.
Preparation, thermal stability, and magnetic properties of Fe---Co---Zr---Mo---W---B bulk metallic glass 总被引:1,自引:0,他引:1
D.Y. Liu W.S. Sun A.M. Wang H.F. Zhang Z.Q. Hu 《Journal of Alloys and Compounds》2004,370(1-2):249-253
A bulk metallic glass (BMG) cylinder of Fe60Co8Zr10Mo5W2B15 with a diameter of 1.5 mm was prepared by copper mould casting of industrial raw materials. The amorphous state and the crystallization behavior were investigated by X-ray diffraction (XRD). The thermal stability parameters, such as glass transition temperature (Tg), crystallization temperature (Tx), supercooled liquid region (ΔTx) between Tg and Tx, and reduced glass transition temperature Trg (Tg/Tm) were measured by differential scanning calorimetry (DSC) to be 891, 950, 59 K, and 0.62, respectively. The crystallization process took place through a single stage, and involved crystallization of the phases -Fe, ZrFe2, Fe3B, MoB2, Mo2FeB2, and an unknown phase, as determined by X-ray analysis of the sample annealed for 1.5 ks at 1023 K, 50 K above the DSC peak temperature of crystallization. Mössbauer spectroscopy was studied for this alloy. The spectra exhibit a broadened and asymmetric doublet-like structure that indicated paramagnetic behavior and a fully amorphous structure. -Fe was found in the amorphous matrix for a cylinder with a diameter of 2.5 mm. The success of synthesis of the Fe-based bulk metallic glass from industrial materials is important for the future progress in research and practical application of new bulk metallic glasses. 相似文献
10.
M. Ohnuma K. Hono S. Linderoth J. S. Pedersen Y. Yoshizawa H. Onodera 《Acta Materialia》2000,48(20):4783-4790
The kinetics of copper clustering and primary crystallization of FINEMET type alloys with the compositions Fe74.5−xSi13.5B9Nb3Cux and Fe77Si11B9Nb3−xCux have been studied by small-angle neutron scattering (SANS) and high-sensitivity differential scanning calorimetry (DSC) in order to explain the different optimized Cu contents, x, for obtaining the highest permeability in these two alloys. SANS results have shown that the alloys with the optimized Cu contents have the finest nanocrystalline microstructures. Kinetic analyses of Cu clustering prior to primary crystallization have shown that the number density of Cu clusters becomes highest at the crystallization stage of -Fe primary crystals in the alloy containing an optimized amount of Cu. 相似文献
11.
The effect of Si addition on the glass-forming ability (GFA) of a NiTiZrAlCu alloy was investigated by using differential scanning calorimetry (DSC), differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The maximum diameter of glassy rods increased from 0.5 mm for the Ni42Ti20Zr25Al8Cu5 alloy (the base alloy) to 2.5 mm for the Ni42Ti20Zr21.5Al8Cu5Si3.5 alloy and to 3 mm for the Ni42Ti19Zr22.5Al8Cu5Si3.5 alloy, when prepared by using the copper mould casting. The GFA of the alloys can be assessed by the reduced glass transition temperature Trg(=Tg/Tl) and a newly proposed parameter, δ(=Tx/Tl − Tg). An addition of a proper amount of Si and a minor substitution of Ti with Zr can enhance the GFA of the base alloy by suppressing the formation of primary Ni(TiZr) and (TiZr)(CuAl)2 phases and inducing the composition close to eutectic. 相似文献
12.
I. Nehdi M. Abdellaoui L. Bessais C. Djega-Mariadassou H. Zarrouk 《Journal of Alloys and Compounds》2003,360(1-2):14-20
The crystallographic and the Curie temperature of the Sm2Fe17−xCrxC2 (x=0.5, 1, 1.5 and 2) carbides have been extensively studied. X-ray diffraction studies have shown that all these alloys are approximately single phases corresponding to the Th2Zn17 type rhombohedral structure with a small amount of -Fe. The amount of this residual -Fe phase decreases with increasing the Cr atomic content. It decreases from 1 wt% for x=0.5 to 0.4 wt.% for x=2. The lattice parameter c increases as a function of the Cr atomic content x from x=0 to x=1.5 and then decreases. This is due to the Cr atoms which prefer to substitute the Fe atoms in the 6c sites located along the c-axis. The lattice parameter a and the unit-cell volume decrease in all substitution ranges. The insertion of the C atoms leads essentially to an increase of the distances between the 9d and 18h sites and the 9d–18f sites. The Curie temperature reaches a maximum value of 583 K for x=1.5 and then decreases to 551 K for x=2. The enhancement of the Tc for lower Cr contents is due to a lowering of the hybridization of the iron atoms with their neighbors, the magnetovolume effect and the reduction of antiferromagnetic interactions. However, the decrease in Tc for higher Cr content is due to the reduction in the number of Fe–Fe pairs due to the magnetic dilution effect. For given interatomic distances, the exchange coupling of the Cr–Cr atoms is not of antiferromagnetic type and the exchange integral of the Cr–Cr pair is higher than that of the Fe–Fe pair. 相似文献
13.
Yu Li Jipeng Miao Yu Sui Qian Cheng Wei Zhang Xianjie Wang Wenhui Su 《Journal of Alloys and Compounds》2008,458(1-2):11-17
A detailed study of step-like metamagnetic transitions in polycrystalline Pr0.75Na0.25Mn1 − xFexO3 (0 ≤ x ≤ 0.30) is reported. It shows that the charge-orbit ordering antiferromagnetic (COOAF) phase in the phase-separated materials is responsible for the step-like metamagnetic transition with extremely sharp steps (width <0.01 T). The fraction of antiferromagnet II (AFII) with larger antiferromagnetic exchange interaction than COOAF is proved to be the effective factor of critical fields (Hc). A model of anisotropy barrier for up/down thermal blocking spins has been proposed to explain the sharp step-like transitions in polycrystalline manganites for the first time. The metamagnetic transitions at 2 K (below the spin blocking temperature TB) and high temperatures are compared. Both sorts of metamagnetic transitions originate from COOAF phase. And the temperature is responsible for the difference between them. 相似文献
14.
Magnetization measurements on zero field cooled (ZFC) and field cooled (FC) samples as a function of temperature where made on Fe0.70−xMnxAl0.30 alloys with 0≤x≤0.10. Our data show the existence of two regimes of the spin glass temperature Tf when increasing the concentration x of the Mn atoms. We found that Tf decreases slowly with increasing x up to x=0.06 and then shows a rapid linear decrease above this concentration. The existence of two regimes of Tf behavior with x may be attributed to the disappearance of ferromagnetic clusters which exist for low values of x (x<0.06). Compared to the Mn-free alloy, the relative changes in Tf are bigger and exceed 40% at x=0.10. The second regime (x>0.06) is associated with more influence of x on Tf. 相似文献
15.
Y.S. Reddy V. Prashanth Kumar E. Nagabhushanam P. Kistaiah C. Vishuvardhan Reddy 《Journal of Alloys and Compounds》2007,440(1-2):6-12
Polycrystalline bulk samples of double layered manganite system La1.2(Sr1−xCax)1.8Mn2O7 (0.0 ≤ x ≤ 0.4) were prepared by sol–gel method. After characterizing the samples using XRD and SEM, their electrical, magnetic and elastic properties were investigated. The lattice parameters and cell volume show a monotonous decrease with increase of Ca content, whereas the grain size is found to increase with increasing Ca content. The value of TIM is found to decrease with Ca content up to x = 0.3 and then a slight increase of TIM is observed. The low temperature upturn of resistivity is attributed to the spin-glass-like behavior, which is also evidenced by the irreversibility observed between ZFC and FC magnetizations. The conduction mechanism above TIM can be explained by Mott VRH model. The present magnetization and ultrasonic studies indicate that the system shows a secondary transition at T*, which decreases with increasing Ca content. Further, the T* seems to be intrinsic to the present double layered manganite system. 相似文献
16.
Gd65Fe20Al15, Gd65Fe15Al20 and Gd70Fe15Al15 bulk amorphous alloys were produced by copper mold casting method with the maximum diameters of 2, 1 and 1 mm, respectively. The crystallization temperature (Tx) and melting temperature (Tm) of the Gd65Fe20Al15 bulk amorphous alloy are 808 and 943 K, respectively. Accordingly, the temperature interval of Tm and Tx, ΔTm (=Tm − Tx), is as small as 135 K and the reduced crystallization temperature (Tx/Tm) is as high as 0.86. The small ΔTm and high Tx/Tm values are presumed to be the origin for the achievement of the high amorphous-forming ability of the Gd–Fe–Al bulk amorphous alloy. The Gd65Fe20Al15, Gd65Fe15Al20 and Gd70Fe15Al15 bulk amorphous cylinders with a diameter of 1 mm exhibit superparamagnetism at room temperature, while the amorphous ribbon shows the paramagnetism at room temperature. Finally, the mechanical properties of Gd65Fe20Al15 bulk amorphous alloys are investigated. 相似文献
17.
Nanocrystalline (Nd,Dy)16(Fe,Co)76−xTixB8 magnets were prepared by mechanical alloying and respective heat treatment at 973–1073 K/30–60 min. An addition of 0.5 at.% of Ti results in increase of coercivity from 796 to 1115 kA/m. Partial substitution of Nd by Dy results in an additional increase of coercivity up to 1234 kA/m. The highest corrosion resistance have magnets with 0.5–0.75 at.% of Ti. Beside the Ti, the Co and Dy content significantly improve the corrosion resistance, too. It was found, that for Ti content smaller than x ≤ 1, the (Nd,Dy)16(Fe,Co)76−xTixB8 powders are single phase. For higher Ti contents (x > 1) the mechanically alloyed powders heat treated at 973 K are no more single phase, and the coercivity as well as corrosion resistance decreases due to the presence of an amorphous phase and -Fe. A heat treatment at a higher temperature (1073 K/30 min) or at 973 K for longer time (1 h) results in the full recrystallisation of the powders. The obtained homogenized structure results in higher corrosion resistance. 相似文献
18.
Feng Xu Zhiming Wang Zuanru Yuan Guang Chen Jianzhong Jiang 《Journal of Alloys and Compounds》2008,458(1-2):261-264
On the basis of the previous work on (Nd62.5Ni37.5)85Al15 alloy, Cu is selected to partially substitute Ni to form (Nd62.5Ni37.5−xCux)85Al15 (x = 0, 10, 20, 30) melt-spun alloys. The glass-forming ability (GFA) of the as-prepared alloys is evaluated by the isochronal differential scanning calorimeter (DSC) measurement. The results show that GFA increases with Cu content according to several different criterions. The isothermal crystallization behaviors in the corresponding supercooled liquid region is discussed by both Johnson–Mehl–Avrami (JMA) equation and some nucleation and growth models. The fitting shows that it is reasonable to divide the whole crystallization processes into two stages. And the fittings with the nucleation and growth models infers that with increasing Cu content, the nucleation mechanism of the primary stage changes from the quenched-in and steady-state nucleation for (Nd62.5Ni37.5)85Al15, to the steady-state nucleation for (Nd62.5Ni27.5Cu10)85Al15 and (Nd62.5Ni17.5Cu20)85Al15, then to the time-dependent nucleation for (Nd62.5Ni7.5Cu30)85Al15. And the dependence of crystallization mechanisms on Cu substitution agrees well with the change of their GFAs. 相似文献
19.
R.K. Jain Ankur Jain Shivani Agarwal N.P. Lalla V. Ganesan D.M. Phase I.P. Jain 《Journal of Alloys and Compounds》2007,430(1-2):165-169
The effect of partial substitution of Ni by Cr in CeNi5 intermetallic compound has been studied by pressure–composition isotherm measurements for different temperatures. The samples were prepared of high purity materials using the standard arc melting technique in argon atmosphere. The structure and the elemental composition of different alloys have been investigated by means of XRD, SEM and EDX techniques. The unit cell volume of the alloy was found to increase with increasing Cr content. In order to calculate the hydrogen storage capacity pressure–composition isotherm has been investigated for CeNi5−xCrx (x = 1, 2) alloys in the temperature and pressure ranges of 293 ≤ T ≤ 333 K and 0.5 ≤ P ≤ 35 bar, respectively. The P–C–T isotherm for different alloys clearly shows the presence of three regions , + β and β. The enthalpy and entropy for the systems has also been calculated using Van’t Hoff plot. The variation of enthalpy and entropy with hydrogen content has also been studied. 相似文献
20.
Polycrystalline samples of potassium doped lanthanum manganites having nanometric crystallite size have been synthesized by pyrophoric method. The Curie temperature (TC) of the prepared samples is found to be strongly dependent on K content and spans between 260 and 309 K. Close to TC, large change in magnetic entropy has been observed in all the samples. The maximum magnetic entropy change observed for samples with different concentration of K, exhibits a linear dependence with the applied magnetic field. Adiabatic temperature change at TC at 1 T also increases with K doping and attains a maximum of 2.1 K for La0.85K0.15MnO3. Estimated relative cooling power of La1−xKxMnO3 compounds is nearly one-third of pure Gd. In addition to the tuneability of TC between 260 and 310 K, higher chemical stability, lower eddy current heating and inexpensive preparation technique; the magnetic entropy change in La0.85K0.15MnO3 compound at 1 T magnetic field is found to be 3.00 J/kg K and is 89% to that known for the prototype magnetic refrigerant (pure Gd). Our result on magnetocaloric properties suggests that La1−xKxMnO3 compounds are attractive as a possible refrigerant for near room temperature magnetic refrigeration. 相似文献