X-RAY-DIFFRACTION AND COMPUTER-SIMULATION STUDIES ON THE STRUCTURE OFHOMOPHASE AND HETEROPHASE INTERFACES IN METALS

We use the Thin Film X-ray Diffraction (TFXD) technique in conjunction with computer simulation methods to obtain detailed information on th e structure of complex interfacial systems in metals. Results for thre e types of interfaces are presented. These are, a Sigma 13 [001] twist homophase boundary in a Au-Cu 10 at. % alloy, a Sigma 26/29 [001] twi st Au-Pd heterophase boundary and finally the Sigma 4/5 [001] twist Ag -Cu heterophase boundary. For the homophase boundary in Au-Cu we demon strate the utility of the X-ray technique in studying the effects of s olute segregation on boundary structure. Calculations predict trends w hich are in agreement with the experimental observations; however the precise magnitudes of the observed effects are not reproduced by the c alculations. For the Au-Pd heterophase boundary semi-quantitative agre ement is obtained between the experiments and the calculations (perfor med using EAM potentials and Molecular Statics), Finally, in the Ag-Cu Sigma 4/5 system, strong X-ray scattering is observed on the BDL, and is correlated with surprisingly large atomic displacements in this bo undary; fairly good agreement is obtained with computer simulated stru ctures. We conclude with speculations on the usefulness of the simple dislocation model in the Ag-Cu [001] twist system.