Effects of milling and annealing on formation and structural characterization of nanocrystalline intermetallic compounds from Ni–Ti elemental powders

Nickel and Titanium elemental powders with a nominal composition Ni–50at.%Ti were mechanical alloyed in a planetary high-energy ball mill in different milling conditions (5, 10, 20, 40 and 60h). The investigation revealed that increasing milling time leads to a reduction in crystallite size, and after 60h of milling, the Ti dissolved in Ni lattice and NiTi (B2) phase was obtained. With milling time, morphology of pre-alloyed powders changed from lamella to globular. Annealing of as-milled powders at 1173K for 900s led to formation of nanocrystalline NiTi (B19′), grain growth and release of internal strain. The results indicated that this technique is a powerful and high productive process for preparing NiTi intermetallic compound with nanocrystalline structure and appropriate morphology. ► The mechanical alloying leads to prepare nanostructured NiTi. ► The compounds exhibit suitable morphology and homogeneous structure. ► The crystallite size in the milled samples decreases with milling time.