Quantification of the amount of ε martensite in a Fe-Mn-Si-Cr-Ni shape memory alloy by means of electron backscatter diffraction

The determination of the volume fraction of epsilon martensite is of crucial importance to study the shape memory behaviour of an iron-based shape memory alloy (SMA). Several techniques have been used in literature trying to obtain a reliable measurement of this volume fraction. The results of these attempts were, however, not satisfying. In the present work, the amount of epsilon martensite in a Fe-Mn-Si-Cr-Ni shape memory alloy was measured by means of electron backscatter diffraction (EBSD) before deformation, after deformation, and after subsequent annealing. Despite the specific nature of the austenite-to-epsilon-martensite transformation, which affected the image quality parameter, it was proven, through the high confidence index, that a correct indexing of the diffraction pattern of epsilon martensite is possible with this technique. The evolution of the epsilon martensite volume fraction could readily be followed with a reasonable accuracy, through the entire processing. These results showed that EBSD has a high potential to quantify the e martensite fraction in an iron-based SMA. (C) 2007 Elsevier B.V. All rights reserved.