Effects of spinning rate on structures and electrochemical hydrogen storage performances of RE-Mg-Ni-Mn-based AB_2-type alloys

La was partially substituted by Ce with the aim of improving the electrochemical hydrogen storage performances ofLa1–xCexMgNi3.5Mn0.5 (x=0, 0.1, 0.2, 0.3, 0.4) alloys, and melt spinning technology was adopted to fabricate the alloys. Theidentification of XRD and SEM reveals that the experimental alloys consist of a major phase LaMgNi4 and a secondary phase LaNi5.The growth of spinning rate results in that the lattice constants and cell volume increase and the grains are markedly refined. Theelectrochemical measurement shows that the as-cast and spun alloys can obtain the maximum discharge capacities just at the firstcycle without any activation needed. With the increase of spinning rate, the discharge capacities of the alloys first increase and thendecline, whereas their cycle stabilities always grow. Moreover, the electrochemical kinetic performances of the alloys first increaseand then decrease with spinning rate growing.

Fatigue small crack growth threshold determination of a high-Nb TiAl alloy at different temperatures by in-situ observation

The purpose of this paper is to estimate the fatigue crack growth threshold of a high-Nb TiAl alloy at the different temperatures based on scanning electron microscopy （SEM） in-situ observation. The results indicated that the fatigue crack growth threshold △Kth of a nearly lamellar high-Nb TiAl alloy with 8% Nb content at room temperature and 750℃ was determined as 12.89 MPa.m^1/2 and 8.69 MPa.m^1/2, respectively. The effect of the elevated temperature on the fatigue crack growth threshold cannot be ignored. At the same time, the early stage of fatigue crack propagation exhibited multicrack initiation and bridge-link behavior.

Tensile properties of tungsten-rhenium wires with nanofibrous structure

In this study, the mechanical properties of tungsten-rhenium wires with nanofibrous microstructure were investigated at both room temperature(RT) and 800?C. The strengthening mechanism associated to the nanofibrous microstructure was discussed. The results showed that the tungsten-rhenium wires with nanofibrous grains exhibited a very high tensile strength reaching values of 3.5 GPa and 4.4 GPa for the coarse(grains diameter of 240 nm) and fine(grains diameter of 80 nm) wires, respectively. With increasing the temperature from RT to 800?C, the tensile strength decreased slightly but still held high values(1.8 GPa and 3.8 GPa). All the fracture surfaces exhibited apparent necking and characteristics of spear-edge shaped fracture surface, indicating excellent ductility of the wires. A model of the strengthening mechanism of these tungsten-rhenium wires was proposed.

Structure and electrochemical performances of Mg20-xYxNi10（x=0-4） alloys prepared by mechanical milling

Mg2Ni-type Mg20-xYxNi10(x=0,1,2,3 and4) electrode alloys were fabricated by vacuum induction melting.Subsequently,the as-cast alloys were mechanically milled on a planetary-type ball mill.The effects of milling time and Y content on the microstructures and electrochemical performances of the alloys were investigated in detail.The results show that nanocrystalline and amorphous structure can be successfully obtained through mechanical milling.The substitution of Y for Mg facilitates the glass forming of the Mg2Ni-type alloy and significantly enhances the electrochemical characteristics of the alloy electrodes.Moreover,the discharge capacity of Y-free alloy monotonously grows with the milling time prolonging,while that of the Y-substituted alloys has the maximum values in the same case.The milling time of obtaining the greatest discharge capacity markedly decreases with Y content increasing.The electrochemical kinetics of the alloys,including high rate discharge ability(HRD),diffusion coefficient(D),limiting current density(IL) and charge transfer rate,monotonously increase with milling time extending.