164 resultados para MAGNESIUM ALLOYS
Resumo:
The discovery of the icosahedral phase (i-phase) in rapidly quenched Ti1.6V0.4Ni1-xCox (x=0.02-01) alloys is described herein. The i-phase occurs in a similar amount relative to the coexisting beta Ti phase. The electron diffraction patterns show the distinct spot anisotropy, indicating that the i-phase is metastable. The electrochemical hydrogen storage performance of these five alloy electrodes are also reported herein. The hydrogen desorption of nonelectrochemical recombination in the cyclic voltammetric (CV) response exhibits the demand for electrocatalytic activity improvement.
Resumo:
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.
Resumo:
The electrochemical deposition of magnesium was investigated in ethereal Grignard salt solution with tetraethylammonium bistrifluoro-methanesulfonimidate additive, using cyclic voltammetry, potentiostatic transients, and scanning electron microscope measurements. The voltammograms showed the presence of reduction and oxidation peaks associated with the deposition and dissolution of magnesium. From the analysis of the experimental current transients, it was shown that the magnesium deposition process was characterized as a three-dimensional nucleation. The deposited product obtained from potentiostatic reduction presented a generally uniform and dense film.
Resumo:
Ti45Zr35Ni13Pd7 alloys are prepared by melt spinning at different cooling rates (v). The phase structure and electrochemical hydrogen storage performance are investigated. When U is 10 m/s, the alloy consists of icosahedral quasicrystalline phase (I-phase), C14 Laves phase and a little amorphous phase. When v increases to 20 or 30 m/s, a mixed structure of I-phase and amorphous phase is formed. Maximum discharge capacity of alloy electrode decreases from 156 mAh/g (v = 10 m/s) to 139 mAh/g (v = 30 m/s) with increasing v. High-rate discharge ability at the discharge current density of 240 mA/g decreases monotonically from 61.2% (v = 10 m/s) to 56.8% (v = 30 m/s).
Resumo:
Ti45Zr35Ni20-xPdx (x = 0, 1, 3, 5 and 7, at%) alloys were prepared by melt-spinning. The phase structure and electrochemical hydrogen storage performances of melt-spun alloys were investigated. The melt-spun alloys were icosahedral quasicrystalline phase, and the quasi-lattice constant increased with increasing x value. The maximum discharge capacity of alloy electrodes increased from 79 mAh/g (x = 0) to 148 mAh/g (x = 7). High-rate dis-chargeability and cycling stability were also enhanced with the increase of Pd content. The improvement in the electrochemical hydrogen storage characteristics may be ascribed to better electrochemical activity and oxidation resistance of Pd than that of Ni.
Resumo:
A new magnesium metal-organic framework (MOF) based on an asymmetrical ligand, biphenyl-3,4',5-tricarboxylate (H3PT) has been synthesized and structurally characterized. MOF Mg-3(BPT)(2)(H2O)(4) (1) consists of 10 hexagonal nanotube-like channels and exhibits pronounced hydrogen-sorption hysteresis at medium pressure.
Resumo:
Three Polypropylene/Poly(ethylene-co-propylene) (PP/EPR) in-reactor alloys produced by a two-stage slurry/gas polymerization had different ethylene contents and mechanical properties, which were achieved by controlling the copolymerization time. The three alloys were fractionated into five fractions via temperature rising dissolution fractionation (TRDF), respectively. The chain structures of the whole samples and their fractions were analyzed using high-temperature gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), C-13 nuclear magnetic resonance (C-13 NMR), and differential scanning calorimetry (DSC) techniques. These three in-reactor alloys mainly contained four portions: ethylenepropylene random copolymer (EPR), ethylene-propylene (EP) segmented and block copolymers, and propylene homopolymer. The increased copolymerization time caused the increased ethylene content of the sample. The weight percent of EPR, EP segmented and block copolymer also became higher.
Resumo:
Mg-8Gd-1Dy-0.3Zn (wt.%) alloy was prepared by high-pressure die-casting technique. The thermal stability, mechanical properties at temperature range from room temperature to 573 K and strengthening mechanism was investigated. The results showed that the die-cast state alloy was mainly composed of fine cellular equiaxed grain. The fine porosity-free skin region was related to the aggregation of rare earth elements. The long lamellar-shaped stacking compound containing Zn and polygon-shaped precipitate were observed along the grain boundaries. The die-cast sample exhibited high mechanical properties and good thermal stability until 523 K.
Resumo:
Microstructures and mechanical properties of the Mg-8Gd-xZn-0.4Zr (x = 0, 1 and 3 wt.%) alloys in the as-cast, as-extruded and extruded-T5 conditions, have been investigated. The peak-aged Mg-8Gd-1Zn-0.4Zr alloy during isothermal ageing at 423 K acquires highest mechanical properties, with the highest ultimate tensile strength and yield tensile strength of 314 and 217 MPa, respectively. Addition of Zn has obvious effect on age hardening responses, especially for 1 wt.% Zn addition. It is due to a uniform distribution of beta' phase which can impede the movement of dislocations. However, addition of 3 wt.% Zn to the Mg-8Gd-0.4Zr alloy leads to a precipitation of Mg3Zn3Gd2 phase (W-phase). This phase is incoherent with interface of the matrix and becomes cores of the fracture in tensile test at room or elevated temperature.
Resumo:
Microstructures and mechanical properties of the Mg-7Y-4Gd-xZn-0.4Zr (x = 0.5, 1.5, 3, and 5 wt.%) alloys in the as-cast, as-extruded, and peak-aged conditions have been investigated by using optical microscopy, scanning electron microscope, X-ray diffraction, and transmission electron microscopy. It is found that the peak-aged Mg-7Y-4Gd-1.5Zn-0.4Zr alloys have the highest strength after aging at 220 A degrees C. The highest ultimate tensile strength and yield tensile strength are 418 and 320 MPa, respectively. The addition of 1.5 wt.% Zn to the based alloys results in a greater aging effect and better mechanical properties at both room and elevated temperatures. The improved mechanical properties are mainly ascribed to both a fine beta' phase and a long periodic stacking-ordered structure, which coexist together in the peak-aged alloys.
Resumo:
Ti44Zr32Ni22Cu2 and Ti41Zr29Ni28Cu2 alloys were prepared by the melt-spinning method. The phase structure was analyzed by X-ray diffraction, and the electrochemical performances of the melt-spun alloys were investigated. The results indicated that the Ti44Zr32Ni22Cu2 alloy was composed of the icosahedral quasicrystals and amorphous phases, and the Ti41Zr29Ni28Cu2 alloy comprised icosahedral quasicrystals, amorphous, and Laves phases. The maximum discharge capacity was 141 mAh/g for the Ti44Zr32Ni22Cu2 alloy and 181 mAh/g for the Ti41Zr29Ni28Cu2 alloy, respectively. The Ti41Zr29Ni28Cu2 alloy also showed a better high-rate dischargeabifity and cycling stability. The better electrochemical properties should be ascribed to the high content of Ni, which was beneficial to the electrochemical kinetic properties and made the alloy more resistant to oxidation, as well as to the Laves phase in the Ti41Zr29Ni28Cu2 alloy, which could work as the electro-catalyst and the micro-current collector.
Resumo:
Mg-7 mass%Gd-x mass%Y (x = 0, 1, 3 and 5) alloys were prepared by casting method, and the microstructures, age hardening behavior and mechanical properties have been investigated. The results show that the addition of Y to the binary Mg-7Gd alloy could reduce the grain size of the as-cast alloys, and enhance the age hardening response and improve mechanical properties during the investigated temperature range. The Mg-7Gd-5Y alloy exhibits maximum ultimate tensile strength and yield strength at peak hardness, and the values are 258 and 167 MPa at room temperature, and 212 and 140 MPa at 250 degrees C, respectively, which is about 1.8 times as high as the Mg-7Gd binary alloy. When x is more than 3, the amount of Mg-5 (Gd,Y) phase is observed at the peak hardness of aged alloys. The significant improvement of the tensile strength at peak hardness is mainly attributed to the fine dispersion of the beta-Mg-5(Gd,Y) precipitate.
Resumo:
The Mg-8Zn-8Al-4RE (RE = mischmetal, mass%) magnesium alloy was prepared by using casting method. The microstructure and mechanical properties of as-cast alloy, solid solution alloy and aged alloy samples have been investigated. Optical microscopy, X-ray diffractometery and scanning electron microscope attached energy spectrometer were used to characterize the microstructure and phase composition for the alloy. Net shaped tau-Mg-32(Al,Zn)(49) phase was obtained at the grain boundary, and needle-like or blocky Al11RE3 phase disperses in grain boundary and alpha-Mg matrix. The tau-Mg-32(Al,Zn)(49) phase disappeared during solution treatment and a new phase of Al(2)CeZn2 formed during subsequent age treatment. The mechanical properties were performed by universal testing machine at room temperature, 150 degrees C and 200 degrees C, separately. The ultimate tensile strength of as-cast alloy is lower compared to an age treatment alloy at 200 degrees C for 12h. The strengths decreased with enhancing test temperature, but elongation has not been effect by age treatment.
Resumo:
The lightest density of Mg has stimulated renewed interest in Mg based alloys for applications in the automotive, aerospace and communications industries. However, Mg in the pure form has relatively low strength, limited ductility and is susceptible to corrosion. Great efforts have been made to improve the mechanical properties of Mg alloys. Alloying Mg with other elements is one of the most important methods. An important class of Mg alloys is the Mg-Zn-RE system (RE = rare earth elements). In recent few decades, a series of new Mg-Zn-RE system alloys have been obtained, and detailed the structure and mechanical properties of the alloys. In this paper, the structure and mechanical properties of the Mg-Zn-RE alloys have been summarized. It showed that these alloys have high strength and they are prospected to be widely used in the future.
Resumo:
A new-type Mg2Si composite was prepared with Mg-9Al-1Zn (AZ91) alloy and vermiculite as raw materials by melt infiltration method. The results show that the microstructure of composite consists of a large amount Of Mg2Si precipitates and a little amount of MgO embedded in alpha-Mg matrix. The Vickers hardness of the composite is obviously higher than that of matrix of AZ91 alloy. Moreover, the composite exhibits excellent compressive property. The ultimate compressive strength of the material is 290 MPa, the yield strength is 175 MPa, and the elongation is about 5%, which are higher than those of AZ91 alloy.