Electrolytic Deposition and Diffusion of Lithium onto Magnesium-9 Wt Pct Yttrium Bulk Alloy in Low-Temperature Molten Salt of Lithium Chloride and Potassium Chloride

The electrolytic deposition and diffusion of lithium onto bulk magnesium-9 wt pct yttrium alloy cathode in molten salt of 47 wt pct lithium chloride and 53 wt pct potassium chloride at 693 K were investigated. Results show that magnesium-yttrium-lithium ternary alloys are formed on the surface of the cathodes, and a penetration depth of 642 mu m is acquired after 2 hours of electrolysis at the cathodic current density of 0.06 A center dot cm(-2). The diffusion of lithium results in a great amount of precipitates in the lithium containing layer. These precipitates are the compound of Mg41Y5, which arrange along the grain boundaries and hinder the diffusion of lithium, and solid solution of yttrium in magnesium. The grain boundaries and the twins of the magnesium-9 wt pct yttrium substrate also have negative effects on the diffusion of lithium.

Microstructures and mechanical properties of extruded Mg-8Gd-0.4Zr alloys containing Zn

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.

Effect of yttrium-rich misch metal on the microstructures, mechanical properties and corrosion behavior of die cast AZ91 alloy

Die cast AZ91-xYmm (x = 0-0.8 wt.%) magnesium alloys with excellent tensile properties and corrosion resistance behavior were successfully prepared by a simple addition of yttrium-rich misch metal (Ymm) to AZ91. Influences of Ymm on the microstructure, mechanical properties and corrosion behavior of AZ91 were investigated. The results showed that addition of Ymm to die cast AZ91 alloy could re. ne the microstructure including primary alpha-Mg and eutectic beta-Mg17Al12. When the content of Ymm reached 0.8 wt.% a small quantity of Al2Y phase would form. The tensile properties were improved greatly with addition of Ymm to AZ91. The creep rate of the AZ91-Ymm alloys, tested at 150 degrees C/50MPa, was one order of magnitude lower than that of AZ91. When addition of Ymm was more than 0.3 wt.%, the salt-spray corrosion resistance of AZ91-Ymm alloys could be 30-40 times of that of AZ91. The improvement of corrosion resistance with addition of Ymm was confirmed by the results of electrochemical polarization experiments. Mechanism of the improvement of mechanical properties and corrosion behavior caused by Ymm was also discussed.

Effect of substituting cerium-rich mischmetal with lanthanum on microstructure and mechanical properties of die-cast Mg-Al-RE alloys

Die-cast Mg-4Al-4RE-0.4Mn (RE = Ce-rich mischmetal) and Mg-4Al-4La-0.4Mn magnesium alloys were prepared successfully and their microstructure, tensile and creep properties have been investigated. The results show that two binary Al-RE phases, Al11RE3 and Al2RE, are formed along grain boundaries in Mg-4Al-4RE-0.4Mn alloy, while the phase compositions of Mg-4Al-4La-0.4Mn alloy mainly consist of alpha-Mg phase and Al11La3 phase. And in Mg-4Al-4La-0.4Mn alloy the Al11La3 phase occupies a large grain boundary area and grows with complicated morphologies, which is characterized by scanning electron microscopy in detail. Changing the rare earth content of the alloy from Ce-rich mischmetal to lanthanum gives a further improvement in the tensile and creep properties, and the later could be attributed to the better thermal stability of Al11La3 phase in Mg-4Al-4La-0.4Mn alloy than that of Al11RE3 phase in Mg-4Al-4RE-0.4Mn alloy.

Effect of Zn concentration on the microstructures and mechanical properties of extruded Mg-7Y-4Gd-0.4Zr alloys

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.

Extended application of edge-to-edge matching model to HCP/HCP (alpha-Mg/MgZn2) system in magnesium alloys

In the present work, the edge-to-edge matching model has been introduced to predict the orientation relationships (OR) between the MgZn2 phase which has hexagonal close packed (HCP) structure and the HCP a-Mg matrix. Based on the crystal structures and lattice parameters only, the model has predicted the two most preferred ORs and they are: (1) [1 1 2 3](alpha-Mg) vertical bar vertical bar]1 1 2 3](alpha-Mg), (0 0 0 1)(alpha-Mg) 0.27 degrees from (0 0 0 1)(MgZn2), (1 0 1 1)(alpha-Mg) 26.18 degrees from (1 1 2 2)(MgZn2), (2) [1 0 1 0](alpha-Mg),vertical bar vertical bar[1 1 2 0](MgZn2), (0 0 0 1)(alpha-Mg) vertical bar vertical bar(0 0 0 1)(MgZn2), (1 0 1 1)(alpha-Mg) 3.28 degrees from ( 1 1 2 2)(MgZn2). Four experimental ORs have been reported in the alpha-Mg/MgZn2 system, and the most frequently reported one is ideally the OR (2). The other three experimental ORs are near versions of the OR (2). The habit plane of the OR (2) has been predicted and it agrees well with the experimental results.

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 -Mg, Mg3YZn6 (I-phase), Mg3Y2Zn3 (W-phase), Mg12YZn (Z-phase), Mg24Y5, MgZn and a small quantity of Al-containing phase. The phase compositions change with various heat treatment conditions. The highest Vickers hardness is obtained in the alloy aged at 200 ◦C for 5 h, the transmission electron microscopy indicated that fine scale Z-phase precipitates in the matrix. The tensile properties of the as-cast and heat-treated alloys were reported.

Microstructures and mechanical properties of Mg-8Gd-0.6Zr-xNd (x=0, 1, 2 and 3 mass%) alloys

Mg-8Gd-0.6Zr-xNd (x = 0, 1, 2 and 3 mass%) alloys were prepared by metal mould casting method, and the microstructures, age hardening responses and mechanical properties have been investigated. The microhardness of the as-cast alloys is increased with increasing Nd content. The age hardening behavior and mechanical properties are enhanced significantly by adding Nd element. The peak ageing hardness of the Mg-8Gd-0.6Zr-3Nd alloy is 103, it is about 1.3 times more than that of the Mg-8Gd-0.6Zr alloy. The aged Mg-8Gd-0.6Zr-3Nd alloy exhibits maximum ultimate tensile strength and yield strength, and the values are 271 and 205 MPa at room temperature, 205 MPa and 150 MPa at 250 degrees C, respectively. Which are about 2 times higher than those of Mg-8Gd-0.6Zr alloy. The improved hardness and strength are mainly attributed to the fine dispersiveness Of Mg5RE and Mg12RE precipitates in the alloy.

Effect of Y for enhanced age hardening response and mechanical properties of Mg-Gd-Y-Zr alloys

In this study, compositional dependence of age hardening response and tensile properties were investigated for Mg-10G(d-x)Y-0.4Zr (x = 1, 3, 5 wt.%) alloys. With increasing Y content, the age hardening response of the alloys enhanced and tensile properties increased. The Mg-10Gd-5Y-0.4Zr alloy exhibited maximum tensile strength and yield strength at aged-peak hardness, and the values were 302 MPa and 289 MPa at room temperature, and 340 MPa and 267 MPa at 250 degrees C, respectively. The strong peak age hardening was attributed to the precipitation of prismatic beta' plates in a triangular arrangement. The cubic shaped beta phase was also observed at grain boundaries. The remarkable improvement in strength is associated with a uniform and high dense distribution of beta' and cubic shaped beta precipitate phases in Mg matrix. Elongation of Mg-10Gd-0.4Zr alloys decreased with increasing Y content, and the elongation of Mg-10Gd-5Y-0.4Zr alloy was less than 3% below 250 degrees C, whereas the alloys containing I wt.% and 3 wt.% Y exhibited higher elongation than 5% at room temperature.

The mechanical properties of magnesium matrix composites reinforced with 10 wt.% W14Al86 alloy particles

The Mg-based metal matrix composite reinforced by 10 wt.% W14Al86 alloy particles has been prepared by mechanical alloying and press-forming process. X-ray diffraction studies confirm the formation of the composite. Microstructure characterization of the samples reveals the uniform distribution of fine W14Al86 alloy. Mechanical properties characterization revealed that the reinforcement of W14Al86 alloy lead to a significant increase in hardness and tensile strength of Mg and AZ91.

Influence of structure and lonic radius on solubility limit in the Mg-Re systems

The relationship between structure, ionic radius and electronegativity and solubility of the various rare-earth elements in Mg was studied. It is found that light RE(La-Sm, Eu, Yb) have more complicated phase relation with Mg but the heavy RE(Gd-Lu, Sc) have the similar crystal structure with magnesium. Also it is found that the less electronegativity difference between Mg and RE is, the more solubility limit of RE in Mg is. The fact of the RE solubility decreased in magnesium with lowering temperature suggests that there is a possibility of Mg supersaturated solid solution formation and it will decomposition during aging. According to the rule, an megnesium alloy with higher strength feature was developed. Their mechanical properties are UTS 347MPa, YTS 290MPa and elongation 12.5% at room temperature.

Microstructures and tensile properties of Mg-8Gd-0.6Zr-xNd-yY (x+y=3, mass%) alloys

Mg-8Gd-0.6Zr-xNd-yY (mass%) alloys which containing different Nd:Y mass ratio of 3:0, 2:1, 1:2 and 0:3 with a constant x + y = 3 were prepared by metal mould casting method, and the microstructure, aging behaviour and tensile properties have been investigated. The fibrous eutectic areas along the boundaries enlarge clearly in the as-cast alloys containing Y element, and the fine grain boundaries and dispersed precipitation are observed in the aged alloys. The Mg-8Gd-0.6Zr-2Nd-Y alloy exhibits notably age-hardening behaviour and the highest mechanical property. The ultimate tensile strength and yield strength of Mg-8Gd-0.6Zr-2Nd-Y alloy in the peak aged hardness are 293 and 221 MPa at room temperature, 248 and 191 MPa at 230 degrees C. The improvement of age-hardening response and tensile properties is mainly attributed to the quadrate-like stable Mg5RE precipitate, which forms readily and orderly in aged Mg-8Gd-0.6Zr-2Nd-Y alloy.

Energy conversion in shape memory alloy heat engine - Part II: Simulation

In this paper, a theoretical model proposed in Part I (Zhu et al., 2001a) is used to simulate the behavior of a twin crank NiTi SMA spring based heat engine, which has been experimentally studied by Iwanaga et al. (1988). The simulation results are compared favorably with the measurements. It is found that (1) output torque and heat efficiency decrease as rotation speed increase; (2) both output torque and output power increase with the increase of hot water temperature; (3) at high rotation speed, higher water temperature improves the heat efficiency. On the contrary, at low rotation speed, lower water temperature is more efficient; (4) the effects of initial spring length may not be monotonic as reported. According to the simulation, output torque, output power and heat efficiency increase with the decrease of spring length only in the low rotation speed case. At high rotation speed, the result might be on the contrary.

Microstructure and Magnetic Properties of Nd60Al10Fe20Co10 Glass-forming Alloy

The microstructural variations of the Nd60Al10Fe20CO10 melt-spun ribbons and the as-cast rod were studied by high resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD) and differential scanning calorimetry. Nano-clusters in glassy m