Retrogression mechanisms simulations of Al-Li alloys

The dissolution kinetics of L1₂ ordered precipitations (δ′-Al₃Li) in a disordered matrix during retrogression heat treatment was investigated on atomic scale using computer simulations based on microscopic diffusion equations (Langevin equation) with the discrete format. The evolutions of atomic pictures and order parameter profiles with time were analyzed, and the retrogression mechanisms of Al-Li alloys were further studied. In the course of retrogression, it is firstly proved that the evolutions of δ′ phase in a disordered matrix is in the order: stoicheometric δ′ phase → non-stoicheometric ordered phase → disordered matrix; and then the retrogression of alloys at metastable field tends to the anti-process of the phase precipitation of alloys at unstable field, while retrogression of alloys at unstable field tends to the anti-process of the phase precipitation of alloys at metastable field.