Crystallization Kinetics and Structure Evolution during Annealing of Ni-Co-Mn-In Powders Obtained by Mechanical Alloying.

The crystallization kinetics and structure evolution during annealing of the Ni _45.5 Co _4.5 Mn _36.6 In _13.4 (at. %) powders produced by mechanical alloying (MA) was investigated. After 70 h and 100 h of MA, the powder consisted of a mixture of amorphous and nanocrystalline body-centered cubic (bcc) phases. We observed the relaxation in the as-received powder. The relaxation temperature (T _re ) increases logarithmically with the annealing time. Annealing above 440 °C results in (1) ordering of L2 ₁ , (2) dissolution of the residual Ni and Mn, (3) tetragonal MnNi phase formation and (4) γ phases precipitation. The activation energies of the B2 → L2 ₁ and Mn (α-Mn) → MnNi (P4/mmm) transformations were calculated.