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 gamma(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 beta'(1) (18R) martensite has only an ordered OR structure with stacking faults. The Cu-14.0Al-4Ni SMA exhibits a relative increase in the inherent and intrinsic damping capacity because the transformed gamma'(1) (2H) martensite exhibits twinning with abundant moveable twin boundaries. (C) 2010 Elsevier B.V. All rights reserved.