X-ray study of the stacking fault density near the hardness maximum of the Au-Ag-Pd system

Abstract

The annealed hardness of certain dental alloys has been measured and found to be in relatively good agreement with the existing hardness map. In addition, lattice parameters, stacking fault densities, and spacing change fractions have been determined for those alloys. The lattice parameters were found to deviate negatively from Vegard's Law. For the alloys studied, the maximum deviation of 0.0091 A occurred at 20 weight % Ag. The average stacking fault density for the five alloys was determined as 0.007, which is within the range for values reported for the Pd-Ag system. The average of the spacing change was found to be 0.06. A computer program has been developed to extract the lattice parameter for a given reflection from step scan data by obtaining midpoints of a peak at various heights above background. Line shape analysis has been performed for one specimen, with the result that the deformation fault density thus obtained agrees well with that obtained from the lattice parameter measurements, and a twin fault density of 0.0045 was measured.