X-ray diffraction characterization of the decomposition behavior of γ Mn phase in a Mn-30at.%Cu alloy

Abstract

In MnCu alloys with more than about 70 at. % Mn, antiferromagnetic phase transition and the closely associated fcc-fct phase transformation take place in the {gamma}{sub Mn} phase which is stable at higher temperatures. The decomposition of {gamma}{sub Mn} phase into Mn-rich and Cu-rich fractions in aged MnCu alloys has been extensively investigated and the boundaries of the metastable miscibility gap for {gamma}{sub Mn} phase were also outlined by means of the Vickers hardness data of aged MnCu alloys. However, the Mn contents of the two decomposed fractions confined by the gap boundaries describe the decomposition behavior during aging only qualitatively, because both Mn content and volume fraction of the decomposed products are influenced not only by aging temperature, but also by alloy composition, aging time and the possible precipitation of {alpha}{sub Mn} phase. The purpose of the present work is to characterize the co-existence of the decomposed two phases by an accurate X-ray scanning, and hence trying to clarify the decomposition process of {gamma}{sub Mn} phase quantitatively.