Effect of vacancies on the damping attenuation of Mn–Cu–Al–0∼3Sn alloys at room temperature

Abstract Mn–Cu alloys are metal materials, which can be used to reduce vibration and noise from machines. With their inner damping mechanism, the alloys show an excellent damping capacity. However, previous reports show that the damping capacity of the alloys often attenuates after placing at room temperature (RT) for a long time. In the present study, the as-cast Mn–Cu–Al–0∼3 wt% Sn alloys were held at RT for 18 months. Their crystallization morphology was observed using backscattered electron (BSE) technology. The phase distribution was characterized using electron backscatter diffraction (EBSD). Their phase structure was analyzed by using X-ray diffraction (XRD). Their starting martensite transformation temperature ( Ms ) and damping capacity were measured by using an inverted torsion pendulum device. It is observed for the first time that the FCT phases mainly form in the dendrites. With vacancies diffusing towards boundaries of phases and twins, the boundaries are pinned and the Ms point declines. Hence, the damping capacity attenuates within 18 months. Moreover, the addition of Sn can weaken the decline trend of Ms point and consequently the IF value of the Sn-contained Mn–Cu alloys attenuates less than that of the none-Sn alloy. This research could help us to understand how to cope with the damping attenuation of the Mn–Cu alloys.