Inherent internal friction of Ti50Ni50−xCux shape memory alloys measured under isothermal conditions

• Ti50Ni50−xCux exhibited higher inherent internal friction peak than Ti50Ni45Cu5.
• Ti50Ni40Cu10 showed a high inherent internal friction at room temperature.
• Ti50Ni40Cu10 had an acceptable inherent internal friction and adequate workability.

Ti50Ni50−xCux (x ⩾ 10) SMAs with (IFPT + IFI)B2→B19 and/or (IFPT + IFI)B19→B19′ peaks exhibited higher damping capacities than the Ti50Ni45Cu5 SMA did with only a (IFPT + IFI)B2→B19′ peak, because the twinning shear values of the {0 1 1} compound twin and {1 1 1} Type I twin in B19 martensite are much lower than that of the 〈0 1 1〉 Type II twin in B19′ martensite. Compared with other Ti50Ni40−xCux SMAs with higher Cu contents, the Ti50Ni40Cu10 SMA was more suitable for high-damping applications because it had the advantages of both an acceptable inherent internal friction and adequate workability. The Ti50Ni40Cu10 SMA showed the highest inherent internal friction of tan δ > 0.03 at room temperature, and is thus a potential high-damping material for use at a steady temperature.