Time: 10:00 a.m.
Place: IC 02-718
Peter Miodownik, Sente Software Ltd.,ThermoTech Ltd., Guildford, United Kingdom
Although technically all the available thermodynamic data bases refer only to equilibrium conditions, there has always been the question of how far such data can also be used to predict transient or non-equilibrium phenomena which are of industrial interest These include Martensitic Transformations, Amorphous alloys, and the formation of planar defects such as Stacking Fault Energies (SFE), and Anti-Phase Boundaries (APB) This presentation will deal with the procedure by which the latter two important quantities can be calculated using just data from a thermodynamic data base and how far such calculations match available experimental data. There has been a revival of interest in SFE calculations in recent years because of its role in determining deformation mechanisms; a historical treatment of the various assumptions will be used to indicate their relative importance since the early calculations made forty years ago.
Very few attempts seem to have been made to calculate the APB energy via a thermodynamic route. The method which will be described here was initially developed in response to an industrial request for the prediction of this parameter in multi-component nickel base superalloys. Despite the fact that many more assumptions need to be made than in the case of SFE calculations, it seems to have good predictive value.
An important additional conclusion is that experimental macroscopic thermodynamic values represent a natural integration of all the various contributory forces acting on more microscopic scales.