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 ( IF PT + IF I ) β 3 ( L 2 1 ) → γ 3 ′ ( 2 H ) peaks exhibit higher damping capacity than the Cu-7.0Zn-11Al SMA with a ( IF PT + IF I ) β 3 ( L 2 1 ) → γ 3 ′ ( 2 H ) peak, because the γ 3 ′ martensite phase possesses a 2H type structure with abundant movable twin boundaries, while the β 3 ′ phase possesses an 18R structure with stacking faults. The Cu-9.0Zn-11Al SMA also possesses a ( IF PT + IF I ) β 3 ( L 2 1 ) → γ 3 ′ ( 2 H ) peak but exhibits low damping capacity because the formation of γ 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.

Keywords

• shape memory alloys (SMAs)
• martensitic transformation
• internal friction
• dynamic mechanical analysis