Molecular dynamics simulation of alloying in a Ti-coated Al nanoparticle

Using molecular dynamics simulation in combination with an embedded atom method potential we analyze the alloying reaction of a Ti-coated Al nanoparticle with equi-atomic fractions and a diameter of about 4.8 nm. The alloying reaction in the nanoparticle occurs mostly as a metastable solid-state alloying process. However, it quickly completes after the melting of the Al-based nanoparticle core. The final product of the reaction is the undercooled liquid Ti50Al50 alloy. The estimated adiabatic temperature, about 1352 K, of the alloying reaction in the nanoparticle is significantly less than the melting temperature, 1494K, of the gamma-TiAl phase in the model. We demonstrate that the amorphous structure of Ti50Al50 alloy is quite stable against crystallization and tends to develop short-range icosahedral order. The possibility of the alloying reaction synthesis of a nanostructured intermetallic TiAl via crystallization of the deeply undercooled liquid Ti50Al50 alloy formed during the self-heating of a highly compacted mixture of crystalline Ti and Al nanopowders is discussed in the light of some related experimental findings [H. Kimura, Philos. Mag., 1996, A 73, 723]. (C) 2011 Elsevier Ltd. All rights reserved.