X-ray diffraction and computer simulation studies on the structure of homophase and heterophase interfaces in metals

Abstract

We use the Thin Film X-ray Diffraction (TFXD) technique in conjunction with computer simulation methods to obtain detailed information on the structure of complex interfacial systems in metals. Results for three 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] twist Au-Pd heterophase boundary and finally the [Sigma] 4/5 [001] twist Ag-Cu heterophase boundary. For the homophase boundary in Au-Cu we demonstrate the utility of the X-ray technique in studying the effects of solute segregation on boundary structure. Calculations predict trends which are in agreement with the experimental observations; however the precise magnitudes of the observed effects are not reproduced by the calculations. For the Au-Pd heterophase boundary semi-quantitative agreement is obtained between the experiments and the calculations (performed 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 boundary; fairly good agreement is obtained with computer simulated structures. We conclude with speculations on the usefulness of the simple dislocation model in the Ag-Cu [001] twist system.