Comparison of the two relaxation peaks in the Ti50Ni48Fe2 alloy

The internal friction (tan δ) and storage modulus of Ti50Ni48Fe2 alloy were studied by dynamic mechanical analysis (DMA). On cooling, a broad relaxation peak with tan δ value as high as 0.2 was detected in R-phase. On heating, another relaxation peak with tan δ value of 0.06 was found in B19′ martensite. Both relaxation peaks disappeared when the alloy was dehydrogenated in a dynamic vacuum furnace. Thus, the origin of both relaxation peaks was attributed to the interaction between twin boundaries and hydrogen atoms, as recently proved in Ti–Ni–Cu alloy. The direct comparison of these two relaxation peaks in the same sample indicates that the height of relaxation peaks increases with the decreasing of twinning shear.