Advanced Materials Research Vol. 815

Abstract: The isothermal sections of the Er-Cu-V and Dy-Cu-V ternary systems at 773K were investigated by experiments. The isothermal section of Er-Cu-V consists of 8 single-phase regions, 13 two-phase regions and 6 three-phase regions. The binary compounds ErCu₅, ErCu₂, ErCu, Er₂Cu₉ and Er₂Cu₇ were observed at 773K. The isothermal section of Dy-Cu-V consists of 7 single-phase regions, 11 two-phase regions and 5 three-phase regions. The binary compounds DyCu₅, DyCu₂, DyCu and Dy₂Cu₉ were confirmed at 773K. No ternary compound was found in the two sections. There is no solubility of V in the Er-Cu and Dy-Cu binary compounds observed.

Abstract: Compton profile measurement of iron polycrystalline sample has been performed with 662 keV γ-radiation from a caesium-137 source. The spectrometer calibration and data corrections for the high energy experiment are discussed. The data are compared with the augmented-plane-wave (APW) and linear combination of atomic orbitals (LCAO) band theoretical Compton profiles of iron. Both theoretical predictions show the band theories overestimate the momentum density at low momenta and underestimate it at intermediate momenta.

Abstract: The hypereutectic Al-20%Si alloy was fabricated by liquid-liquid mixing of Controlled Diffusion Solidification (CDS), and the mixing interface of two precursor alloys as well as the effects of pouring temperature during liquid-liquid mixing process on microstructure of size, morphology and distribution of primary silicon were studied. The results show that the size of primary phase decreases as the pouring temperature decreases, and the distribution of primary phase becomes uniform, but the morphology changes unobvious. Meanwhile, the liquid-liquid mixing interface is divided into four areas: low temperature alloy area, interface front area, fine grain area and high temperature alloy area.

Abstract: High entropy alloys emerge as a new type of advanced metallic materials, which have received increasing attentions from material engineers around the world. In addition to high entropy effect based on equiatomic or near-equiatomic and containing five or more principal elements, they exhibit a cocktail effect resulting from interactions among all the elements and the indirect effects of the various elements on the performances. In this study, according to high entropy alloy design principles, corrosion-resistant elements such as Al, Ni, Cr and Mo were used to improve the anticorrosion property, Fe, Co, B and Si as solid solution elements were added to promote the formation of solid solutions with simple structure, and the wear-resisting property increased.

Abstract: LaNi₅ alloy is one of the promising materials for hydrogen storage. It has good activation property, fast reaction rate and moderate plateau pressure. However, some of its hydrogen storage properties will change after repeated hydriding/dehydriding cycles, which limits its practical application. Therefore, this paper investigated the cycling properties of LaNi₅ alloy by volumetric method. The results showed that the reaction rate increased with cycling. The hydriding/dehydriding hydrogen content decreased with cycling. For hydriding reaction, the equilibrium pressure increased with cycling, while it decreased for dehydriding at 40°C and 60°C. After 100 cycles, the LaNi₅ alloy has been severely pulverized and oxygenated. The oxidation products include LaNiO₂, La₂NiO₄, La₂NiO_4.18 and LaNiO₃. The JMA model was found to fit the kinetic data well, suggesting a nucleation and growth controlling mechanism. The intrinsic reaction rate constant k_a increases from 21.87 s^-1to 24.81 s^-1, while the activation energy decreases from the initial value of 19459 to 19373 J/mol after 100 cycles.

Abstract: The charge and discharge process of heat transfer fluid in the solar thermal power generation system was simulated. A thermal cycle test repeated between high temperature and low temperature was put on prepared Bi-Pb-Sn-Cd low-melting-point alloy. The thermal physical performance tests were put on the alloy samples which experimented with 200, 400 and 800 times thermal cycle test respectively. The test results show that the specific heat capacity of alloy sample declines slowly and the thermal conductivity increases slowly. The phase change temperature of alloy increases slightly and latent heat decreases slightly with the thermal cycle continuing.

Abstract: The hot deformation behavior of 7050aluminum alloy was investigated by hot compression tests in the temperature range of 573-773K and the strain rate ranging from 0.001s^-1 to 10 s^-1.The flow curves showed that the flow stresses increase with the increase of strain rate or the decrease of temperature.In order to determine the optimal processing conditions, hot processing maps were established based on experimental data and Dynamic Materials Model. The processing maps indicate that instability occur at low temperature and high strain rate. The optimum hot working region is the domain in the temperature range of 673-723K and strain rate range of 0.001-0.01 s^-1,where typical recrystallization was observed in the optical microstructures.

Abstract: A fibrous monolith cemented carbide with WC-6%Co as cell and WC-20%Co as cell boundaries was produced through hot co-extrusion process in this paper. The density, hardness, transverse rupture strength (TRS) and fracture toughness (K_Ic) of the fibrous monolith cemented carbide were tested, and the fracture and crack propagation were observed by metalloscope and Scanning Electron Microscope. The result shows fibrous monolith structure design could effectively improve the TRS and the K_Ic of WC/Co cemented carbide without a significant decrease of hardness. It is the reason of high transverse rupture strength and fracture toughness that WC-20%Co can absorb more fracture energy in order to slow, prevent, or deflect crack propagation, proved by metalloscope and scanning electron microscope.

Abstract: The effects of flux components and compositions of solder alloys on the wettability of the Sn-Zn alloys on aluminum surface was investigated. The results show that the wettability of the Sn-9Zn solder on aluminum substrate improved with flux of double solvents composed of diethanolamine and triethanolamine, which is better than single solvent. When flux is composed of 3% zinc fluoborate as activator and 30% triethanolamine plus 67% diethanolamine as double solvents, the spreading area of the Sn-9Zn solder reaches to 75%. Trace addition (0.002%-0.005%) of Al results in significant improvement of the wettability of the Sn-9Zn based solder. However, additions of Bi or Sb are not beneficial to the wettability of the solder on aluminum substrate.