Fe-57 Mossbauer spectroscopic and magnetic studies of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy)

Mossbauer spectra for Fe atoms in the series of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) compounds were collected at 4.2 K. The ratio of 14.5 T/mu(B) between the average hyperfine field B-hf and the average Fe magnetic moment mu(Fe)(MS), obtained from our data, in Y3Fe29-xVx is in agreement with that deduced from the RxTy alloys by Gubbens et al. The average Fe magnetic moments mu(Fe)(MS) in these compounds at 4.2 K, deduced from our Mossbauer spectroscopic studies, are in accord with the results of magnetization measurement. The average hyperfine field of the Fe sites for R3Fe29-xVx at 4.2 K increases with increasing values of the rare earth effective spin (g(J) - 1) J, which indicates that there exists a transferred spin polarization induced by the neighboring rare earth atom.

Fe-57 Mossbauer spectroscopic and magnetic studies of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy)

Mossbauer spectra for Fe atoms in the series of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) compounds were collected at 4.2 K. The ratio of 14.5 T/mu(B) between the average hyperfine field B-hf and the average Fe magnetic moment mu(Fe)(MS), obtained from our data, in Y3Fe29-xVx is in agreement with that deduced from the RxTy alloys by Gubbens et al. The average Fe magnetic moments mu(Fe)(MS) in these compounds at 4.2 K, deduced from our Mossbauer spectroscopic studies, are in accord with the results of magnetization measurement. The average hyperfine field of the Fe sites for R3Fe29-xVx at 4.2 K increases with increasing values of the rare earth effective spin (g(J) - 1) J, which indicates that there exists a transferred spin polarization induced by the neighboring rare earth atom.

Effects of rare earth on the structure and properties of Mg–6Zn–5Al–4Gd–1RE (RE = Ce or Y) alloys

The microstructures and mechanical properties of Mg-6Zn-5Al-4Gd-1RE (RE = Ce or Y) alloys were investigated. The addition of Ce or Y obviously refines the grain size for the Mg-6Zn-5Al-4Gd-based alloy, while the Y element has a better refining effect. The Ce and Y show different grain-refining mechanisms: Ce addition mostly promotes the growth of secondary dendrite, while Y addition mainly increases the heterogeneous nucleation sites.

Dry sliding wear behavior of magnesium alloys

Dry sliding tests were performed on as-cast magnesium alloys Mg97Zn1Y2 and AZ91 using a pin-on-disc configuration. Coefficients of friction and wear rates were measured within a load range of 20-380 and 20-240 N at a sliding velocity of 0.785 m/s. X-ray differactometer, scanning electron microscopy, tensile testing machine were used to characterize the microstructures and mechanical properties of Mg97Zn1Y2 alloy and AZ91 alloy. Worn surface morphologies of Mg97Zn1Y2 and AZ91 were examined using scanning electron microscopy.

Microstructure and mechanical properties of Mg-12.3Zn-5.8Y-1.4Al alloy

Microstructure and mechanical properties of as-cast and heat-treated Mg-12.3Zn-5.8Y-1.4Al (ZYA1261) alloy were investigated. The phase compositions of the as-cast alloy are alpha-Mg, Mg3YZn6 (I-phase), Mg(3)y(2)Zn(3) (W-phase), Mg12YZn (Z-phase), Mg24Y5, MgZn and a small quantity of Al-containing phase.

Microstructures and mechanical properties of as-cast Mg–5Al–0.4Mn–xNd (x=0, 1, 2 and 4) alloys

Mg-5Al-0.4Mn-xNd (x=0, 1, 2 and 4wt.%) alloys were prepared by metal mould casting method. The microstructures and mechanical properties were investigated. The results demonstrated that Al11Nd3 phase was formed and mainly aggregated along the grain boundaries with the addition of Nd. Meanwhile, the grain sizes were greatly reduced with the increasing Nd content.

Effect of Nd on the microstructure, mechanical properties and corrosion behavior of die-cast Mg-4Al-based alloy

Die-cast Mg-4Al-0.4Mn-xNd(x = 0, 1, 2, 4 and 6 wt.%) magnesium alloys were prepared successfully and influences of Nd on the microstructure, mechanical properties and corrosion behavior of the Mg-4Al-0.4Mn alloy have been investigated. The results showed that with the addition of Nd binary Al2Nd phase and Al11Nd3 phase. which mainly aggregated along the grain boundaries, were formed, and the relative ratio of above two phases was in correlation with the Nd content in the alloy. Meanwhile, the grain sizes were greatly reduced with the increasing Nd content. It was found that due to the addition of Nd both the tensile properties and corrosion resistance were improved substantially.

Electrochemical corrosion behavior of Mg-5Al-0.4Mn-xNd in NaCl solution

The electrochemical corrosion behavior of Mg-5Al-0.4Mn-xNd (x = 0, 1, 2 and 4 wt.%) alloys in 3.5% NaCl solution was investigated. The corrosion behavior of the alloys was assessed by open circuit potential measure, potentiodynamic polarization, and electrochemical impedance spectroscopy. The electrochemical results show the intermetallic precipitates with Nd behave as less noble cathodes in micro-galvanic corrosion and suppress the cathodic process. During corrosion, Al2O3 and Nd2O3, in proper ratio, is incorporated into the corrosion film, and enhances the corrosion resistance.

Preparation and characterization of As-cast and hot-rolled Mg-3Al-0.5Mn-0.5Zn-1MM alloy

Mg-3Al-0.5Mn-0.5Zn-1MM alloy was prepared by metal mould casting method. The as-cast ingot was homogenized and then hot-rolled at 673 K with total thickness reduction of 65%. Microstructure and mechanical properties of the as-cast and hot-rolled samples were investigated. The results showed that the as-cast sample mainly consisted of alpha-Mg, beta-Mg17Al12, Al10Ce2Mn7, and Al11RE3 (RE = La and Ce) phases. The average grain size of the sample homogenized at 673 K was about 240 gm, and it was greatly refined to about 7 mu m by dynamic recrystallization for the hot-rolled sample.

Effect of La-Mg-based alloy addition on structure and electrochemical characteristics of Ti0.10Zr0.15V0.35Cr0.10Ni0.30 hydrogen storage alloy

Effect of La-Mg-based alloy (AB(5)) addition on Structure and electrochemical characteristics of Ti0.10Zr0.15V0.35Cr0.10Ni0.30 hydrogen storage alloy has been investigated systematically. XRD shows that the matrix phase structure is not changed after adding AB(5) alloy, however, the amount of the secondary phase increases with increasing AB(5) alloy content. The electrochemical measurements show that the plateau pressure Ti0.10Zr0.15V0.35Cr0.10Ni0.30 + x% La0.85Mg0.25Ni4.5Co0.35Al0.15 (X = 0, 1, 5, 10, 20) hydrogen storage alloys increase with increasing x, and the width of the pressure plateau first increases when x increases from 0 to 5 and then decreases as x increases further, and the maximum discharge capacity changes in the same trend.

Thermal-shock resistance of LnMgAl(11)O(19) (Ln = La, Nd, Sm, Gd) with magnetoplumbite structure

Lanthanide hexaaluminates including LaMgAl11O19, NdMgAl11O19, SmMgAl11O19 and GdMgAl11O19 were synthesized via Sol-Gel method. Due to the anisotropic crystal growth, these oxides crystallize in the form of platelets and the platelet thickness increases with the decrease of rare-earth ionic radius. It was observed that the thermal-shock resistances of LaMgAl11O19, NdMgAl11O19 and SmMgAl11O19 oxides were superior to 8YSZ as proved by water quenching tests. In addition, the thinner the platelet. the more interstices are retained in the sintered specimen, and the better thermal-shock resistance the oxide has. Based on SEM images, it can be seen that the SmMgAl11O19 sample exhibits a mixture of the intergranular and transgranular fracture after thermal cycling failure.

Precipitates formed in a Mg-7Y-4Gd-0.5Zn-0.4Zr alloy during isothermal ageing at 250 degrees C

The ageing behavior of an extruded Mg-7Y-4Gd-0.5Zn-0.4Zr alloy during ageing at 250 degrees C has been investigated. Two types of phases have been observed during the ageing process. One is a lamellar phase with a 14H long periodic stacking structure, the other is the beta' phase with an ellipsoidal morphology. The increased mechanical properties of the peak-aged alloy are mainly ascribed to the presence of both of these phases at peak hardness.

Effects of cerium on the microstructure and mechanical properties of Mg-20Zn-8Al alloy

Mg-20Zn-8Al-xCe(x=0-2 wt.%) alloys were prepared by metal mould casting method, the effects of Ce on the microstructure and mechanical properties of the alloys were investigated. The results showed that the dendrite as well as gram size were refined by the addition of Ce, and the best refinement was obtained in 1.39% Ce containing alloy. The main phases in the as cast alloys were alpha-Mg and tau-Mg-32 (Al, Zn)(49), and Al4Ce phase was found in the alloys contained more than 1.39% Ce. The addition of Ce improved the mechanical properties of the alloys. The strengthening mechanism was attributed to grain refinement and compound reinforced.

Effect of La/Ce ratio on the structure and electrochemical characteristics of La0.7-xCexMg0.3Ni2.8Co0.5 (x=0. 1-0.5) hydrogen storage alloys

The effect of La/Ce ratio on the structure and electrochemical characteristics of the La0.7-xCexMg0.3Ni2.8Co0.5 (x = 0.1, 0.2, 0.3, 0.4, 0.5) alloys has been studied systematically. The result of the Rietveld analyses shows that, except for small amount of impurity phases including LaNi and LaNi2, all these alloys mainly consist of two phases: the La(La, Mg)(2)Ni-9 phase with the rhombohedral PuNi3-type structure and the LaNi5 phase with the hexagonal CaCU5-type structure. The abundance of the La(La, Mg)(2)Ni-9 phase decreases with increasing cerium content whereas the LaNi5 phase increases with increasing Ce content, moreover, both the a and cell volumes of the two phases decrease with the increase of Ce content. The maximum discharge capacity decreases from 367.5 mAh g(-1) (x = 0.1) to 68.3 mAh g(-1) (x = 0.5) but the cycling life gradually improve. As the discharge current density is 1200 mA g(-1), the HRD increases from 55.4% (x = 0.1) to 67.5% (x = 0.3) and then decreases to 52.1% (x = 0.5). The cell volume reduction with increasing x is detrimental to hydrogen diffusion D and accordingly decreases the low temperature dischargeability of the La0.7-xCexMg0.3Ni2.8Co0.5 (x = 0.1-0.5) alloy electrodes.

Crystallographic and electrochemical characteristics of La0.7Mg0.3Ni3.5-x (Al0.5Mo0.5)(x) (x=0-0.8) hydrogen storage alloys

The crystal structure, hydrogen storage property and electrochemical characteristics of the La0.7Mg0.3Ni3.5-x(Al0.5Mo0.5), (x=0-0.8) alloys have been investigated systematically. It can be found that with X-ray powder diffraction and Rietveld analysis the alloys are of multiphase alloy and consisted of impurity LaNi phase and two main crystallographic phases, namely the La(La, Mg)(2)Ni-9 phase and the LaNi5 phase, and the lattice parameter and the cell volume of both the La(La, Mg)(2)Ni-9 phase and the LaNi5 phase increases with increasing A] and Mo content in the alloys. The P-C isotherms curves indicate that the hydrogen storage capacity of the alloy first increases and then decreases with increasing x, and the equilibrium pressure decreases with increasing x. The electrochemical measurements show that the maximum discharge capacity first increases from 354.2 (v = 0) to 397.6 mAh g(-1) (x = 0.6) and then decreases to 370.4 mAh g(-1) (x= 0.8). The high-rate dischargeability of the alloy electrode increases lineally from 55.7% (x=0) to 73.8% (x=0.8) at the discharge current density of 1200 mA g(-1). Moreover, the exchange current density of the alloy electrodes also increases monotonously with increasing x.