Ti-based bulk amorphous and quasicrystalline materials prepared by warm process

Amorphization and crystallization behaviors of Ti₇₀Ni₁₅Al₁₅ and Ti_41.5Zr_41.5Ni₁₇ powders during mechanical alloying (MA) and subsequent heat treatments are studied. Fully amorphous powders are prepared by MA of the elemental powder mixture of the nominal composition of Ti₇₀Ni₁₅Al₁₅. During.continuous heating of the amorphous powders in DSC, two exothermic events are observed. The first exothermic event corresponds to the formation of a supersaturated α-Ti phase of hexagonal close-packed structure. The growth kinetic of the α-Ti phase is sluggish forming nanostructured α-Ti matrix. The second exothermic event is associated with the solid-state transformation of the meta-stable α-Ti into the equilibrium phases, Ti₂Ni and Ti₃Al. Amorphous powders are prepared after MA for more than 30 hours in the mixture of elemental powders with the nominal composition of Ti_41.5Zr_41.5Ni₁₇. The amorphous powder transforms into the quasicrystalline phase in the temperature range of 300-400 °C during continuous heating in DSC. Based on the observed amorphization and crystallization behavior Ti₇₀Ni₁₅Al₁₅ and Ti_41.5Zr_41.5Ni₁₇ powders, bulk materials consisting of amorphous phase with small fraction of nanocrystals in the Ti-Ni-Al system and quasicrystalline phase in the Ti-Zr-Ni system can be fabricated in a hot press using MA powders.