Combined thermodynamic and kinetic computational simulation of heat treatments: precipitation of metastable phases in Al alloys

摘要

The combination of calculations dealing with thermodynamic properties and diffusion processes allows a physically-meaningful simulation of precipitation processes. The present results are part of a broader project, the final goal of which is theprediction of microstructures produced by actual heat treatments of commercial Al alloys. As a first step in the description of higher component systems, the binary system Al-Cu is analysed here. The growth of one particle of metastable phase from asupersaturated Al-1.75 at. % Cu alloy is simulated at different temperatures.First the solvus lines for the metastable phases GP zones, θ" andθ' were thermodynamically described by means of the THFRMO-CALC calculation package. Some of the necessary thermodynamic data on the stable phases were obtained from already existing databanks (THFRDAS/SGTE, COST-507). On the other hand, due to the absence of a database for the metastable phases, these had to be directly compiled from the literature and used after a thorough assessment. The obtained thermodynamic description was thenused, in combination with actual diffusion data, to simulate the precipitate growth during an annealing at constant temperature. For this purpose, the program DICTRA was used.