Materials under extreme conditions

Materials under extreme pressures and temperatures can behave extremely different from materials under ambient conditions. There is a need to quantify such behavior in order to ensure performance of structural materials under extreme conditions and, at the same time, new materials, with improved properties, could be generated due to this novel behavior. Understanding mechanical deformation of metals at high strain rate requires studies of the equation of state, properties of point, line, planar, and volumetric defects, and effect of loading rate. There are a number of results on non-equilibrium molecular dynamics (MD) simulations of loading of face centered cubic (fcc) metals, but almost nothing has been done for bcc metals, despite their relevance for technological applications.

We propose to carry out large-scale MD simulations of loading up to high pressures and temperatures, with up to several hundred million atoms, for body-centered-cubic (bcc) metals, including Fe, Ta, V and Mo, using embedded-atom method (EAM), modified-EAM (MEAM) and bond-order potentials. Our computational samples will include defective crystals, in order to mimic experimental conditions used by several collaborators abroad. We will obtain X-ray diffraction patterns and defect microstructure as it can be observed by dynamic diffraction and electron microscopy from these experiments. The resulting relaxed microstructure will be tested for improved mechanical properties. Our MD simulations will help parametrizing various constitutive models for continuum-level simulations, carried out as part of this effort, aiding in the connection of MD results to engineering applications.

Subsidios

This work is funded by the National Agency for Scientific & Technological Promotion (http://www.agencia.gov.ar) under PICT2008-1325.

Integrantes y colaboradores

Diego R. Tramontina (UN Cuyo)

Justin Wark, Andrew Higginbotham (Oxford)

Marc A. Meyers (UCSD)