Deformation-induced structural transformation in boron-doped Ni76Al24

The paper describes the effect of cold deformation on the stability of L12 structured hypostoichiometric Ni76Al24(B) alloy. During cold rolling, the order parameter decreases with the degree of deformation. After 85% cold rolling, the material transforms to DO22 structure from its initial L12 structure. The lattice parameters are measured as a = 3.567 Å and c = 7.188 Å having a c/a ratio of ∼2.015. After annealing, the metastable structure transforms back to its original L12 structure. The DO22 structure can be derived from the L12 structure by local rearrangement of the Ni atoms as antisites. The activation energy of the reverse transformation is similar to that for the diffusion of Ni atoms in Ni3Al.