Comparison of Dislocation Accumulation Behavior upon Thermal Cycling in Ti-30Ni-20Cu and Ti-39Ni-11Pd Shape Memory Alloys

Accumulation behavior of transformation -induced dislocation upon thermal cycling of Ti-30Ni-20Cu which satisfies the triplet condition (TC) was compared to that of Ti-39Ni-11Pd which is known as low hysteresis shape memory alloy designed by the condition that the middle eigenvalue of lattice deformation is 1 (CC1). The dislocation density was determined by the Williamson -Hall method. Although the 0.2% proof stress of the Ti-30Ni-20Cu alloy was about half that of the Ti-39Ni-11Pd alloy, the dislocation accumulation behavior was almost the same in both alloys. The formation of transformation -induced dislocation is effectively suppressed by satisfying TC, more than equivalently to satisfying CC1 only. TC is suggested to be a new guideline to design durable shape memory alloy. [doi:10.2320/matertrans.MT-M2023202]