Reaction mechanism study of Al/Ti alloy thin films under thermal stimulation

Abstract

Alloy films are widely used in energy-containing materials to enhance combustion efficiency and heat release, and to improve explosive or propulsive performance. However, studies on the reaction mechanism under thermal stimulation are scarce. In this study, the reaction properties of Al/Ti nanolayers under different conditions are systematically investigated using molecular dynamics simulations (NVT and NVE) and atomic embedding potentials. By constructing accurate atomic models ((Al/Ti)_II, (Al/Ti)_III, and (Al/Ti)_IV) and using appropriate potential energy functions, the reaction was firstly relaxed at 1500 K for 20 ps, followed by reaction simulations under adiabatic conditions for 6 ns. The study reveals the microscopic mechanism of the Al/Ti nanolayer reaction, covering the key processes of reaction triggering, interfacial evolution and temperature change. The main results are as follows: at the junction of the Al and Ti layers, Ti atoms are exfoliated from the solid state and migrate to the Al liquid phase, triggering the reaction. In the “liquid-like” structure (reaction temperature in the range of 1840–1900 K), the interface atoms alloy with the Ti surface, and as the temperature increases, the Ti atoms absorb heat and transform from solid to liquid, and contact with the Al melt to drive the reaction. With the increase of the reaction period, the alloying of the transition layer is completed in advance, and the shorter the period ((Al/Ti)_II, (Al/Ti)_III, and (Al/Ti)_IV), the faster the reaction rate (0.203, 0.398, and 0.707 K ps⁻¹). In the adiabatic stage, the Al/Ti system exhibits self-sustained reaction properties, and the temperature increase promotes the alloying reaction. Eventually, the system reaches equilibrium. This study provides an important theoretical reference for alloy film design and reaction energy control. Simulations provide insight into the high-temperature properties, while experiments demonstrate the behavior of the alloy at lower temperatures, providing a basis for the practical application of the material in industry, and together the two studies build a more comprehensive picture of the material's behavior.