Cooling rate dependence of the properties for Ti110Al14V4 alloy investigated by ab initio molecular dynamics

Abstract

The structural evolution and kinetic properties of Ti110Al14V4 alloy under two constant cooling rates are comprehensively studied by ab initio molecular dynamics simulations. A variety of statistical methods are used to progressively analyze the changes in local atomic structure with temperature under different cooling rates. It is revealed that for slow cooling, the icosahedron and face-centered cubic (FCC) cluster dominate in the melt before the system transforms into a body-centered cubic (BCC) crystalline phase at a temperature of about 1600 K. For fast cooling, the system melts from 2600 to 1600 K, then turns into solid glass at 1400 K, and finally forms a crystalline and amorphous mixture. This is a process in which the icosahedron competes with the FCC structure, indicating that the Ti110Al14V4 alloy has a very poor glass-forming ability because of the fragility of Ti110Al14V4 liquids at high temperature. Furthermore, under a fast cooling rate, the self-diffusion coefficient obeys the Arrhenius function at high temperature but conforms to the mode coupling theory when approaching the critical temperature. Finally, through the five-fold local symmetry parameters and viscosity, a direct relationship between structure and dynamics is established, confirming that structural evolution is the root cause of slow dynamics. This discovery provides a new perspective on the structural mechanism of dynamic arrest in the Ti110Al14V4 melt.