Kadau, Kai; Germann, Timothy C.; Lomdahl, Peter S.; Hoolian, Brad Lee; Kadau, Dirk; Entel, Peter; Kreth, Magnus; Westerhoff, Frank; Wolf, Dietrich:

Molecular-dynamics study of physical properties in sintered nano-particles

In: Technical Proceedings of the 2002 International Conference on Computational Nanoscience and Nanotechnology (Nanotech 2002 Vol. 2)
Cambridge, Mass. [u.a.]: Computational Publ. (2002), S. 338-339
ISBN: 0-9708275-6-3, 0-9708275-8-X
Buchaufsatz / Kapitel / Fach: Physik
Nano-crystalline metals, in which the size of grains is in the nanometer range, exhibit physical properties different from ordinary polycrystalline materials, thus these materials are of technological interest [1]. One example is the increasing hardness with decreasing grain size due to dislocation immobilisation at the grain boundaries (Hall-Petch effect). However when decreasing the grain size below a critical value, sliding processes between the grains decrease the hardness which is called the reverse Hall-Petch effect [2, 3]. Another interesting aspect is the phase stability of a polymorphic material and structural phase transitions such as martensitic transformations in Fe-based alloys [4] in nano-crystalline materials. Here we report on the first molecular-dynamics simulations [5] in combination with contact-dynamics [6]. We used the contact-dynamics method to determine the arrangement of a number of particles with a given size-distribution. Using this arrangement as the initial configuration of randomly oriented nano-particles and modeling the sintering-process on the atomic scale within the framework of molecular-dynamics simulations, where the atomic interactions were described by an embedded-atom method (EAM) potential specially designed to model the Fe-Ni alloy [8, 7] and Al [9]. After a simulation time of some 100 ps a more or less dense polycrystal has formed, whereas the density depends on the temperature and pressure. Interesting physical properties of the formed nano-phase material such as the afore mentioned reverse Hall-Petch effect and martensitic transformations were studied and compared to single-crystals.