Nanocrystalline phase formation and extension of solid solubility by mechanical alloying in Ti-based systems

Abstract

The formation of nanocrystalline phases in TiNi, TiCu systems has been studied by mechanical alloying. In all the above systems, mechanical alloying of the pure metal powder mixture (initial powder particle size - 45 μm) has resulted in the formation of particles of about 20 nm size. The particle size after mechanical alloying has been determined from the X-ray peak broadening using Scherrer's formula (L = 0.9 λ/ β cos θ) after separating out the contribution from lattice strains. Large extensions of solid solubility when compared to the equilibrium solid solubility have been observed after mechanical alloying, which has been attributed to the formation of nanocrystals. The X-ray peak shifts after mechanical alloying have indicated a solid solubility of about 18 at.% and 10 at% Ti in Ni and Cu respectively in the case of binary TiNi and TiCu systems which are far in excess of the equilibrium solid solubility for the respective systems.