ON THE INTERPRETATION OF HREM IMAGES OF PARTIALLY ORDERED ALLOYS

The ordering for 11/20 alloys has been studied by high-resolution elec tron microscopy (HREM). The distribution of the intensity maxima in th e HREM image have been statistically examined, which provides a profou nd basis for the image interpretation. Processing of the HREM images a llows ''dark-field'' images to be obtained, exhibiting a two-dimension al distribution of those columns which contain the most information in order to interpret the short-range order correlations. Pair correlati ons and higher cluster correlations between projected columns can be v isualised, providing unique information about the ordering as retrieve d from an experimental result without any other assumption. The method has been applied to Au4Cr and to Au4Mn to interpret the quenched shor t-range order state and the transition to long-range order.