Internal friction of R-phase and B19′ martensite in equiatomic TiNi shape memory alloy under isothermal conditions

The intrinsic internal friction IFI of R-phase and B19′ martensite are composed of static internal friction IFS and dynamic internal friction IFD. The tan δ values of IFSR and IFSB19′ are both proportional to σ0/υ1/2 and are related to the stress-assisted motions of twin boundaries. The tan δ values of IFSR are higher than those of IFSB19′ is owing to the softer storage modulus E0 in R-phase. The tan δ values of IFDB19′ are linearly proportional to T˙/υ1/2. The occurrence of relaxation peak at ≈−60 °C is found to come from the IFSB19′, instead of the IFDB19′.