Advanced Materials Research Vols. 690-693

Abstract: In this paper, developed a non-aluminum die casting magnesium alloys were studied based on Mg-xGd-Y-Zr（x=6, 8, 12 wt.%）alloys in cold chamber press. The microstructures and mechanical properties of die casting GWK alloys have been investigated using OM, SEM, XRD, EDS and mechanical property test. The experimental results show that with increasing Gd content of Mg-xGd-Y-Zr alloys, the tensile strength increase, but elongation decrease. In particular, die casting GWK alloys after short-term and low-temperature solid solution treatment (T4) have a small variation in grain size and more uniform microstructures, and the second phases distribute at the grain boundaries in form of discontinuous rod shape or granule shape, which result in an obvious improvement in tensile mechanical properties of alloys. The Mg-12Gd-3Y-0.5Zr die casting alloy exhibit maximum tensile strength after solution heat treatment, and the value is 269MPa at room temperature. The effect of solution heat treatment on die casting Mg-xGd-Y-Zr alloys was also discussed.

Abstract: This paper explains sintering properties of Al2O3-70(referred to as the 70 green sample) natural mullite that was prepared by the process of homogenization, wet grinding, vacuum extrusion and high-temperature tunnel kiln sintering. The results show that 70 green sample's dehydroxylation temperature started in 528 °C; 70 green sample's sintering densification started in 1500 °C; 70 green sample had not completed sintering in the 1600 °C, and at this temperature, to prolong the holding time also won't realize densification. After sintering at 1600 °C, the sample's bulk density is 2.82. In this sample, the mullite phase was uniform distribution, density, low porosity and most are closed porosity.

Abstract: The application of Magnesium alloy as a lightweight material in high-speed trains can realize an effect of largely reducing the weight of the trains. However, magnesium alloy extrusion profiles are rarely applied in the high-speed trains. A7003-T5 and 5052 aluminum alloys are used as the high-speed train seat-back’s material on high-speed trains recently. The experimental data indicates that the strength of the AZ31B magnesium alloy is 1.3 times of that of 5052 aluminum alloy and the strength of the ZK60A magnesium alloy is 1.21 times of that of A7003-T5 aluminum alloy.The FE analysis results indicate that if the ZK60A and AZ31B magnesium alloy is used as the material of the high-speed seat back instead of the A7003-T5 and 5052 aluminum alloy, it will have a weight loss of the backrest for approximately 33%. In addition, the application of ZK60A and AZ31B magnesium alloy has more advantages in energy-saving, environmental protection and safety control.

Abstract: The copper specimen was fabricated through liquid die forging under optimum technical parameter, and the die forging copper was annealed under different conditions. The effect of annealing treatment on the microstructure, strength, hardness and electric conductivity of die forging copper was investigated. The results show that the microstructure of die forging copper was changed into equiaxed grain when the treating temperature was less than 250 °C and treating time was less than 2.0 h. The restoration and recrystallization happened during treatment and the obtained crystal grain size became smaller. The strength of die forging copper decreased after annealing treatment owing to the decreasing of dislocation density and concentration of supersaturated vacancy. The hardness of die forging copper also dropped to some extent. The electric conductivity of die forging copper was increased by 5.2% after annealing treatment because the concentration of supersaturated vacancy and dislocation density was decreased obviously.

Abstract: Alloying elements such as Fe, Zr and Mg in Cu were added by direct addition of powders and by feeding of cored alloy wire filled with alloying element powder in a lab scale furnace. The yield of Fe was the highest for both addition methods. Cored wire feeding was significantly more effective than the direct powder addition into the copper melt. Though the yield of Mg was almost zero by the addition of Mg powder, it was increased remarkably by the Mg cored wire feeding. Through the calculation of the model which was designed based on an industrial scale line, it was confirmed that the yield of the alloying elements was affected by the wire feed rate and the thickness of the copper tube that envelops an alloy powder.

Abstract: In order to explore the best way of zinc alloy cooling, respectively adopting air cooling, water cooling, oil cooling and cooling in the furnace, to study its influence on the zinc alloy material properties. The results show that the oil cooling mode can improve the comprehensive properties of zinc alloy.

Abstract: The melt-spun method, X-ray diffractometer (XRD), differential scanning calorimeter (DSC),vickers microhardness measurement and bend test were adopted to study the effects of Cr substitution of Mo on the glass forming ability (GFA), thermal stabilities and mechanical properties of (Fe_0.58Co_0.42)₇₃Mo_17-xCr_xZr₁₀(x=0,3,6,9,12,17at%) ribbons. The results show that when x ranges from 9~17, the ribbons are in an amorphous state. With increasing the Cr content, all the characteristic temperatures including T_gT_xT_p move towards to the lower temperature regions, but the supercooled regionsΔT_x increases, the GFA of sample is rising. In the bend test, all the amorphous ribbons can be classified asductile.

Abstract: Today, magnesium (Mg) alloys are recognized alternatives to iron and aluminum to reduce the weight of structural materials. This contribution was performed to provide information on the flammability of magnesium alloys through investigation of the ignition temperature of selected Mg alloys. The test was performed in a muffle furnace with dynamic heating program. Also were performed tests of chemical composition of studied specimens.

Abstract: A novel process of solid-oxide-oxygen-ion conducting membrane (SOM) technique has been investigated to produce Cr metal directly from Cr₂O₃ in molten CaCl₂. The sintered porous Cr₂O₃ pellet was employed as the cathode while liquid copper, saturated with graphite powder and encased in a one-end-closed yttria-stabilized-zirconia (YSZ) tube, acted as the anode. The particle sizes and porosity of the cathode pellets are important factors that have significant impact on the electrolysis process. The optimal experimental condition is pellet forming pressure 4MPa, sintering and electrolytic temperature 1150°C, cell voltage 3.5V, electrolysis time 2h.

Abstract: The microstructures and electrochemical corrosion behaviors of die-cast Mg-4Al-0.4Mn-xPr (x=0, 1, 4 wt.%) alloys have been investigated. Electrochemical behaviors of all alloys are described by open circuit potential test, potentiodynamic polarization test and electrochemical impedance spectroscope in 3.5 wt.% NaCl solution. The results show that the α-Mg grain is refined and the continuous net β phase appears gradually with increasing the content of Pr in the Mg-4Al-0.4Mn alloys. Moreover, the β phase plays a role of galvanic cathode in AM40 alloy and corrosion barrier in Pr-containing alloys, respectively. Electrochemical measurements show that Pr can improve corrosion resistance of Mg-4Al-0.4Mn alloy in the 3.5 wt.% NaCl solution, and corrosion rate decreases with increasing Pr content.