Computational investigation of constitutional liquation in Al-Cu alloys

Constitutional liquation means the local eutectic melting of second-phase particles in a matrix at temperatures above the eutectic temperature and below the solidus of the alloy, which may occur in the heat-affected zone (HAZ) during welding. In the present paper, the constitutional liquation in the Al-Cu system was computationally investigated using the DICTRA program coupled with critically assessed thermodynamic and kinetic databases. Computer simulated results are in quantitative agreement with existing experimental data. The computational procedures for obtaining the critical heating rate to avoid constitutional liquation are demonstrated. The critical heating rate was found to be inversely proportional to the square of the precipitate size. The present computational procedures can be readily extended to predict the susceptibility of multicomponent commercial alloys to constitutional liquation during welding with available thermodynamic and kinetic databases.