Heterogeneities and strain glass behavior: Role of nanoscale precipitates in low-temperature-aged Ti_48.7Ni_51.3 alloys

A frozen short-range, strain-ordered state has been observed in several doped ferroelastic/martensitic alloys. The reported strain glass behavior has been attributed to atomic-scale point defects such as dopant atoms. We report here how nanoscale precipitates can also lead to such glassy behavior. Nanosized, randomly distributed Ti₃Ni₄-like precipitates, produced by aging/annealing at 473 K for 3 h, prohibit the B2 → B19′ martensitic transition that occurs in a precipitate-free state. The strain glass transition is characterized by a mechanical susceptibility/modulus anomaly with Vogel-Fulcher type frequency-dependence, ergodicity-breaking, invariance in average structure and nanosized strain domains. Our work emphasizes that heterogeneities or in general disordering effects in ferroelastics will also give rise to signatures characteristic of strain glass behavior.