Effect of alloying with Al and Cr on the microstructure, damping capacity and high-temperature oxidation behaviors of Fe-17Mn damping alloys

Fe-17Mn is a commonly used damping alloy with excellent strength, wide temperature range, and low cost. Nevertheless, its poor resistance to corrosion and its low high-temperature oxidation resistance limit its application. In this study, the high-temperature oxidation resistance was enhanced by alloying with Cr and Al. The oxidation resistance was analyzed at 500 degrees C. Besides, the effects of alloying with Cr and Al on the microstructure and damping capacity of Fe-17Mn alloys were also investigated. Alloying with Cr and Al changed the Ms temperature of the alloys and affected the solid phase composition. Lower Ms temperatures produced higher gamma-austenite and epsilon-martensite phase fractions. Al had a more significant effect on the reduction of the Ms temperature than Cr, because Al sharply increased the stacking faults energy that acted as a barrier for the gamma -> epsilon phase transformation. Alloying with Cr and Al decreased damping capacity at low and high amplitudes. This decrement was a result of the reduction of the stacking faults probability and the 8-martensite. At high amplitudes, the pinning of dislocations was the main factor deteriorating damping capacity. While Cr increased the weak pinning points, Al increased the strong pinning points. The oxidation kinetics obeyed an exponential function model, and alloying with Cr and Al significantly decreased the rate constant. The oxide scales of the Fe-17Mn binary alloy, which easily peeled off during cooling, mainly consisted of M2O3 and MnFe2O4 with several voids. The outmost of the substrate formed a ferritic layer due to the selective oxidation of Mn at high temperatures. MnO was found at the interface between the oxide scales and the ferritic layer. Although alloying with Cr and Al was not enough to form oxide scales, Cr and Al oxides dispersed in the Mn oxide scales and enriched the top of the ferritic layer hindering the inward diffusion of oxygen. (C) 2019 Elsevier B.V. All rights reserved.