Berlin 2012 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 54: Computational Materials Modelling VIII - Mechanical Properties and Strain

MM 54.4: Vortrag

Donnerstag, 29. März 2012, 16:30–16:45, TC 006

Role of coherency strain in the stabilization of metastable precipitate of the Mo-C binary system — •Sankari Sampath, Rebecca Janisch, Suzana G Fries, and Alexander Hartmeier — ICAMS, Bochum, Germany

The precipitation of second phases in metals and metallic alloys is an important phenomenon that has a high influence on the mechanical properties of the material. In a previous computational study, the precipitation behavior of (bct)carbide, MoCx at a grain boundary in Mo(bcc) has been investigated. The study showed that there is a significant strain contribution to the interface energy of the lattice misfit. In the present project, the Mo-C binary system is being studied thoroughly by varying carbon concentrations in the system. The aim is to quantify this strain contribution to the interface energy by means of ab-initio Density Functional Theory using VASP code such that the stabilization of the metastable phase(bct) could be carried out.

The structural stability of various phases of the Mo-C system has been analyzed and compared with experimental results where available.The phase diagram has been obtained using Thermo-Calc and the stable phases agree with our predictions at T=0K. A metastable phase(bct), which is not present in the phase diagram, has been observed experimentally by HREM as a semi-coherent precipitate. We assume that it is stabilized by the precipitate interface energy. Starting with the coherent interface for Mo(001) and MoCx(001),the study has been extended to gamma surface calculations that yield possible Burgers vectors for misfit dislocations.