A new approach to the analysis of short-range order in alloys using total scattering

Abstract

a b s t r a c tIn spite of its influence on a number of physical properties, short-range order in crystalline alloys has received little recent attention, largely due to the complexity of the experimental methods involved. In this work, a novel approach that could be used for the analysis of ordering transitions and short-range order in crystalline alloys using total scattering and reverse Monte Carlo (RMC) refinements is presented. Calculated pair distribution functions representative of different types of short-range order are used to illustrate the level of information contained within these experimentally accessible functions and the insight into ordering which may be obtained using this new method. Key considerations in the acquisition of data of sufficient quality for successful analysis are also discussed. It is shown that the atomistic models obtained from RMC refinements may be analysed to identify directly the Clapp configurations that are present. It is further shown how these configurations can be enhanced compared with a random structure, and how their degradation pathways and the distribution of Warren-Cowley parameters, can then be used to obtain a detailed, quantitative structural description of the short-range order occurring in crystalline alloys.

Analysis of short-range order in Cu3Au using X-ray pair distribution functions

“…To provide a quantification of and description of SRO present in a large box model, the following descriptors may be employed. The use of the descriptors for such analysis is described in detail in our previous work [4].…”

“…The Warren-Cowley α−parameters and Clapp configuration enhancement factors, calculated as described in our previous theoretical work [4], are shown in Fig. 4.…”

“…The output boxes from the RMC runs were analysed using the methods described in previous work [4], calculating the enhancement factors and Warren-Cowley parameters for these systems. The Warren-Cowley α-parameters for the first ten co-ordination shells, obtained using this method, are shown in Fig.…”

“…In this current work, a systematic measurement of the short-range order in Cu 3 Au has been made using in situ X-ray total scattering. Analysis of these data using the RMC method represents the first application of the method outlined in our previous theoretical work [4] to real experimental data and demonstrates the potential of total scattering to provide a better understanding of ordering occurring in metallic systems beyond analyses based on Warren Cowley α-parameters alone.…”

“…However, to data, total scattering has rarely been applied to the study of short-range order (SRO) in alloys. In a previous paper [4], a method by which SRO in metal alloys can be determined from total scattering data was proposed. In this paper, X-ray total scattering data from Cu 3 Au have been used to demonstrate this analysis in action.…”