Effect of Co additions on the damping properties of Cu-Al-Ni shape memory alloys

This study investigates the effect of Co additions on the damping properties of Cu-13.5Al-4Ni-xCo and Cu-14.0Al-4Ni-xCo (x = 0-2 wt%) shape memory alloys (SMAs). The Cu-14.0Al-4Ni SMA exhibits a higher inherent and intrinsic internal friction (IFPT + IFI) peak than the Cu-13.5Al-4Ni SMA, but its (IFPT + IFI) peak temperature is below 0 degrees C. Adding Co into the Cu-14.0Al-4Ni SMA can effectively increase the (IFPT + IFI) peak temperature and reduce the grain size of the alloys. The grain size of the Cu14.0Al-4Ni-xCo SMAs decreases from approximately 300 um to below 50 um when the Co content increases from 0 to 2 wt%. The (IFPT + IFI) peak temperature for the Cu-14.0Al-4Ni-xCo SMAs increases from -0.1 degrees C to 77.7 degrees C when the Co content increases from 0 to 1 wt%, but their tan delta values decrease from 0.0402 to 0.0090 simultaneously. The Cu-14.0Al-4Ni-2Co SMA does not exhibit an observable (IFPT + IFI) peak. The tan 6 values of the (IFPT + IFI) peaks decrease with increasing Co content because the movements of the parent/martensite phase interfaces and twin boundaries are impeded by the increased amounts of grain boundaries and gamma(2) phase precipitates. Among these Cu-Al-Ni-Co SMAs, the Cu-14.0Al-4Ni-0.5Co SMA is more suitable for high-damping applications as it possesses an (IFPT + IFI) peak with tan 8 close to 0.02 at approximately 50 degrees C. (C) 2020 Elsevier B.V. All rights reserved.