Showing papers by "Rang-su Liu published in 2013"

On the heredity and evolution of icosahedral clusters during the rapid solidification of liquid Cu50Zr50 alloys

Abstract: A molecular dynamics simulation is performed to investigate the heredity characteristics of icosahedral clusters during the rapid solidification of liquid Cu 50 Zr 50 alloy at a cooling rate of 5 K/ns. The analysis from a cluster-type index based on the H–A bond-type index shows that (12 0 12 0) icosahedra and their distorted configurations (12 8/1551 2/1541 2/1431) play a key role in the formation of glassy alloys. At T g , the numbers of (12 0 12 0) and (12 8/1551 2/1541 2/1431) basic clusters significantly increase and most of which are Cu-centered Cu 6 Zr 7 , Cu 7 Zr 6 and Cu 5 Zr 8 clusters. An inverse tracking investigation on the configuration evolution during the rapid solidification further reveals that the configuration heredity of icosahedral clusters in the super-cooled liquid is an intrinsic feature of the rapidly solidified Cu 50 Zr 50 alloys, but the onset of configuration heredity merely emerges in the super-cooled liquid region of T m – T g . Below T g , the perfect heredity of icosahedra is dominant and a distinctly ascent in heredity fraction f i takes place at T g . Relative to (12 8/1551 2/1541 2/1431) distorted icosahedra, the standard (12 0 12 0) icosahedra are of high structural stability and large genetic ability, and most of which are passed down by means of the configuration rather than the chemical order.

Evolutions of Micro-clusters of Biodegradable Mg 3 Ca 7 Potential Medical Implant Alloy

Abstract: The molecular dynamics simulation calculation on the micro-clusters evolution properties of liquid Mg3Ca7 during the rapid solidifications has been performed. Results indicate that the icosahedron micro-cluster plays key role in the glass transition which happens at about 600 K; it suggests that the formation and evolution mechanism of icosahedral order is important for the corrosion resistance of medical implant material of Mg- and Mg-Ca based alloys. It is also found that the icosahedron structure is unstable in the liquid and supercooled liquid until the glass transition occurs.

DYNAMIC MECHANISM OF LIQUID–GLASS TRANSITION FOR Mg7Zn3 ALLOY

Abstract: The dynamic mechanism of liquid–glass transition for Mg7Zn3 alloy is studied by the molecular dynamics simulations. The temperature dependences of dynamic properties during the liquid–glass transition are investigated. Two relaxation processes are clearly observed near the glass transition temperature. The diffusivity deviates from the Arrhenius law after the melting temperature Tm and satisfies the power law before the dynamic singularity temperature Tc owing to the cage effect. The solid- and liquid-like atoms are defined according to the vibration characteristic of atoms. It is found that the solid-like atoms have higher local packing density, lower mobility and potential energy than the liquid-like ones. Based on the evolutions of solid- and liquid-like atoms, the atomic mechanism of dynamic liquid–glass transition is systematically elucidated, which is consistent with the potential energy landscape.