Correlation between electron work functions of multiphase Cu-8Mn-8Al and de-alloying corrosion

Low energy electron emission microscopy (LEEM) was used to measure local transition energy that was directly correlated to electron work function (EWF) of multiphase manganese-aluminum bronze alloys. We developed color mapping to distinguish the EWF of multiple phases and clarified that the EWF were in the following order: EWF of alpha > EWF of beta > EWF of kappa (EWF alpha > EWF beta > EWF kappa). De-alloying corrosion took place due to the micro-galvanic cell at grain boundaries before it propagated into the beta phase that had lower EWF than the alpha phase. The alpha phase was a stable phase because it contained high Cu while the beta phase contained high Al and Mn. In addition, XRD analysis showed that the texture coefficient of the b phase revealed that almost all of the grains had (2 2 0) orientation, the lowest EWF compared to (1 1 1) and (2 0 0). Furthermore, transmission electron microscopy illustrated that there were fine Cu3Mn2Al precipitates in the Cu2MnAl matrix of the beta phase. These precipitates formed micro-galvanic cells which played an important role in accelerating de-alloying corrosion. (C) 2018 Elsevier B.V. All rights reserved.