Influence of chemical composition on the damping characteristics of Cu–Al–Ni shape memory alloys

Abstract

Cu– XAl–4Ni shape memory alloys (SMAs) are capable of martensitic transformation across a wide temperature range through the precise adjustment of their chemical composition from X = 13.0 to 14.5. In addition, the variations in chemical composition significantly influence the internal friction characteristics of Cu– XAl–4Ni SMAs. Cu– XAl–4Ni SMAs with a higher content of Al exhibit lower internal friction peaks due to decreases in the amount of transformed martensite and the formation of γ 2 phase precipitates. The damping capacity of the inherent and intrinsic internal friction for Cu–13.5Al–4Ni SMA is extremely low due to the fact that the transformed β ′ 1 ( 18 R ) martensite has only an ordered 9R structure with stacking faults. The Cu–14.0Al–4Ni SMA exhibits a relative increase in the inherent and intrinsic damping capacity because the transformed γ ′ 1 ( 2 H ) martensite exhibits twinning with abundant moveable twin boundaries.