Effect of Mechanical Alloying and Sintering on Ni–Ti Powders

Commercially pure nickel-titanium powders were mechanically milled in a vertical attritor mill under protective atmosphere for various times from 10 to 24 hr. Products were then compacted and sintered at different temperatures for different times. Amorphization and interatomic phase formation were determined by X-ray diffractometry, scanning electron microscopy, and differential scanning calorimetry. Porosity, virtual density, transition temperatures, and the amount of Ni3Ti first increased and then decreased with the milling time. Presence of oxygen in the milling atmosphere showed partial crystallization of NiTi intermetallic compound accompanied by titanium oxide formation.