Dissolution of Al₂Cu Precipitate in Al2024 Additively Manufactured by Electron Beam Melting

Abstract

Samples built by the additive manufacturing experience various thermal cycles during the process. This, as a result, defines the final microstructure of the samples. Herein, the dissolution of θ‐Al2Cu precipitate along the building direction during electron beam melting process is aimed at. Induced thermal cycles cause the layers to experience critical temperatures. The results show that the average fraction area of precipitates is decreased from 3.34% to 2.63% and finally to 2.02% by moving along the building direction from the top to the bottom. This is due to the fact that the first deposited layers are kept at temperatures more than 520 °C for longer times, which is higher than the critical temperature of Al2Cu dissolution. Because of the solubility limit of Cu in the matrix, precipitates are not fully dissolved. Comparing the ratio of the integration area of the strongest θ diffraction peak to that of the α matrix at different locations, the dissolution is also confirmed by X‐ray diffraction (XRD) results. The results of the tensile test also demonstrate a decline of about 29% in the mechanical performance by moving from the top to the bottom, which can be attributed to the precipitates’ dissolution and grain coarsening.