Free energy simulation of grain boundary segregation and thermodynamics in Ni(3-x)Al(1+x).

摘要

The free energy simulation method is employed to study segregation to (Sigma)5 and (Sigma)13 (001) twist grain boundaries and their free energies in ordered Ni(sub 3-x)Al(sub 1+x). In the temperature range studied (300--900K), it is shown that there is almost no segregation, strong Al segregation, and weak Ni segregation to the grain boundary for the stoichiometric, Al-rich, and Ni-rich bulk compositions respectively. It is also shown that the segregation is limited to a few (002) planes around the grain boundary and its magnitude decreases with increasing temperature. For Al-rich bulk composition, it is demonstrated that segregation at low temperature substantially lowers the grain boundary free energy. 8 refs., 7 figs.