In this paper, the compression test on the bulk nanocrystalline sliver ( n Ag) with average grain size of 50 nm was made. The stress-strain curves under different strain rates were obtained by test. The test results show that the mechanical behavior of n Ag is rate-dependent, and the dynamic compress yield stress are about 1.5 times of that n Ag in static test condition; The effect of strain harding on n Ag is smaller than that of coarse-grained silver (c Ag) in plastic deformation; The relationship between the yield strength and the logarithm of strain rate is approximately linear.
Absback.We performed a least-squares fit for crystal potentials derived by APW band structure calculations for monatomic, as well as diatomic, structures. The potential is described by an eighth order polynomial multiplied by an exponential function. The fitted potentials yield eigenvalues, for a variety ofk points, within 2-3 mRyd of the first-principles APW results We have also discovered that starting with the fitted potential at a given lattice constant and using the potential in the interstitial region (muffin-tin zero) as a single
In this paper, the analysis and method of forming for cold extrusion die of precision gears is analyzed. The basic principle and progress of gear closed forming based on exchanging axles on the common hydraulic press are introduced. The mould structure is introduced.
In this paper, melt-spinning technology was used for preparing Mg20Ni10-xCox (x = 0, 1, 2, 3, 4) hydrogen storage alloys. The influences of both the Co substitution and the melt spinning on the the physical and electrochemical hydrogen storage kinetics of the alloys were investigated. The XRD, SEM and TEM characterization exhibits that the as-spun Co-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys substituted by Co display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. The Co substitution gives rise to forming secondary phase MgCo2 without altering the Mg2Ni major phase of the alloys. The measurement of the physical and electrochemical hydrogen storage kinetics of the alloys shows that both the melt spinning and the substitution of Co for Ni markedly improve the physical hydriding and dehydriding kinetics and the electrochmeical kinetics (HRD) of the alloys.
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