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

Abstract

The crystallization kinetics and structure evolution during annealing of the Ni45.5Co4.5Mn36.6In13.4 (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 degrees C results in (1) ordering of L2(1), (2) dissolution of the residual Ni and Mn, (3) tetragonal MnNi phase formation and (4) gamma phases precipitation. The activation energies of the B2 -> L2(1) and Mn (alpha-Mn) -> MnNi (P4/mmm) transformations were calculated.