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We studied Ni 50+ x Ti 50-x with compositions between x= 0.1 and 2.0, by performing 47 Ti and 49 Ti nuclear magnetic resonance (NMR) measurements over a temperature range from 4 K to 400 K. Substitutional disorder has been shown to interrupt the displacive phase transition in these materials and induce a reversible freezing process akin to that of spin glasses or relaxor ferroelectrics. The unfrozen state is characterized by cooperative nanoscale dynamical displacements. Our work probes the local dynamics of this system by NMR spin-lattice relaxation time (T 1) measurements, and points to large fluctuation in the parent system as well as in the substituted strain glasses. The Vogel-Fulcher relation has been extensively used to parameterize the relaxation dynamics in glassy systems. However, our results point instead to more standard Arrhenius behavior, implying a nonstandard glass freezing process. High …