7,828 research outputs found
Synthesis of single-component metallic glasses by thermal spray of nanodroplets on amorphous substrates
We show that single component metallic glasses can be synthesized by thermal spray coating of nanodroplets onto an amorphous substrate. We demonstrate this using molecular dynamics simulations of nanodroplets up to 30 nm that the spreading of the nanodroplets during impact on a substrate leads to sufficiently rapid cooling (10^(12)–10^(13) K/s) sustained by the large temperature gradients between the thinned nanodroplets and the bulk substrate. However, even under these conditions, in order to ensure that the glass transition outruns crystal nucleation, it is essential that the substrate be amorphous (eliminating sites for heterogeneous nucleation of crystallization)
Liquid metals: early contributions and some recent developments
We illustrate in this contribution the progress in the theoretical study of
liquid metals made in the last decades, starting from the example of liquid
gallium and the early work in Jean-Pierre Badiali's group. This was based on
the combination of the perturbation theory with pseudo-potentials for the
electrons and the liquid state theory for the ions. More recent developments
combining ab initio and classical molecular dynamics simulations are finally
illustrated on the example of glass forming alloys.Comment: 12 pages, 8 figure
Molecular Dynamics Simulations of Lead and Lithium in Liquid Phase
Pb17Li is today a reference breeder material in diverse fusion R&D programs worldwide. Extracting dynamic and structural properties of liquid LiPb mixtures via molecular dynamics simulations, represent a crucial step for multiscale modeling efforts in order to understand the suitability of this compound for future Nuclear Fusion technologies. At present a Li-Pb cross potential is not available in the literature. Here we present our first results on the validation of two semi-empirical potentials for Li and Pb in liquid phase. Our results represent the establishment of a solid base as a previous but crucial step to implement a LiPb cross potential. Structural and thermodynamical analyses confirm that the implemented potentials for Li and Pb are realistic to simulate both elements in the liquid phase
From metallic glasses to nanocrystals: Molecular dynamics simulations on the crossover from glass-like to grain-boundary-mediated deformation behaviour
Nanocrystalline metals contain a large fraction of high-energy grain
boundaries, which may be considered as glassy phases. Consequently, with
decreasing grain size, a crossover in the deformation behaviour of nanocrystals
to that of metallic glasses has been proposed. Here, we study this crossover
using molecular dynamics simulations on bulk glasses, glass-crystal
nanocomposites, and nanocrystals of Cu64Zr36 with varying crystalline volume
fractions induced by long-time thermal annealing. We find that the grain
boundary phase behaves like a metallic glass under constraint from the abutting
crystallites. The transition from glass-like to grain-boundary-mediated
plasticity can be classified into three regimes: (1) For low crystalline volume
fractions, the system resembles a glass-crystal composite and plastic flow is
localised in the amorphous phase; (2) with increasing crystalline volume
fraction, clusters of crystallites become jammed and the mechanical response
depends critically on the relaxation state of the glassy grain boundaries; (3)
at grain sizes 10 nm, the system is jammed completely, prohibiting pure
grain-boundary plasticity and instead leading to co-deformation. We observe an
inverse Hall-Petch effect only in the second regime when the grain boundary is
not deeply relaxed. Experimental results with different grain boundary states
are therefore not directly comparable in this regime.Comment: 19 pages, 17 figure
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