Determining transformation temperatures of equiatomic TiNi shape memory alloy by dynamic mechanical analysis test

Strain variation induced by martensitic transformation of Ti50Ni50 shape memory alloy (SMA) is investigated by dynamic mechanical analysis (DMA) test. The extent of the positive and negative strain variation is mainly associated with the softening and hardening rate of storage modulus E0, respectively. The occurrence of the strain variation is related to DMA instrument design since the stress accommodation cannot keep up with the drastic change of the E0 softening/hardening rate during transformation. Strain variation is very sensitive and can rapidly respond to the E0 change, thus martensitic transformation temperatures of SMAs associated with a multi-stage transformation can be determined precisely from the onset/finish of the strain variation.

► The extent of positive strain variation is associated with the softening rate of E0.
► Strain variation is very sensitive and can rapidly respond to the E0 change.
► Transformation temperatures can be determined from the onset of the strain variation.