Atomic diffusion at the Ni–Ti liquid interface using molecular dynamics simulations

Nickel Titanium (NiTi) alloys are produced by heating raw Ni and Ti in high temperature. In this stage, Ni and Ti atoms diffuse and mix to form an alloy. Despite the importance of technology, Ni and Ti atoms’ diffusion mechanism, however, still remains unelucidated. We performed molecular dynamics simulations for 1 ns to investigate the diffusion process of Ni–Ti liquid at temperatures of 2000, 2200, 2400, and 2600 K. Our results show that the diffusion coefficient increases with increasing temperature. In the 2000–2400 K temperature range, Ni atoms diffuse faster by 1.4% to 16.3% than Ti atoms. On the other hand, the liquid Ni structure becomes less dense at higher temperatures (T = 2600 K), such that Ti atoms with a smaller mass can diffuse more rapidly. From the calculations, the diffusion activation energy of Ni is 0.2 eV higher than that of Ti.