Damping characteristics of inherent and intrinsic internal friction of Cu-Zn-Al shape memory alloys

Abstract

Damping properties of the inherent and intrinsic internal friction peaks (IFPT + IFI) of Cu-xZn-11Al (x = 7.0, 7.5, 8.0, 8.5, and 9.0 wt. %) shape memory alloys (SMAs) were investigated by using dynamic mechanical analysis. The Cu-7.5Zn-11Al, Cu-8.0Zn-11Al, and Cu-8.5Zn-11Al SMAs with (IFPT + IFI)β3(L21) → γ'03 (2H) peaks exhibit higher damping capacity than the Cu-7.0Zn-11Al SMA with a (IFPT + IFI)β3(L21) → γ'03 (2H) peak, because theγ'03 martensite phase possesses a 2H type structure with abundant movable twin boundaries, while theβ'03 phase possesses an 18R structure with stacking faults. The Cu-9.0Zn-11Al SMA also possesses a (IFPT + IFI)β3(L21) → γ'03 (2H) peak but exhibits low damping capacity because the formation of g phase precipitates inhibits martensitic transformation. The Cu-8.0Zn-11Al SMA was found to be a promising candidate for practical high-damping applications because of its high (IFPT + IFI) peak with tan δ > 0.05 around room temperature.