Structure Determination of Al 2 CuMg Precipitates in AlCu 15 Mg 5 Alloys by High-Resolution Electron Microscopy

In this paper, the structure of the S - phase (Al₂CuMg) precipitate in Al matrix in high-copper AlCu₁₅Mg₅ alloys has been determined by using a high-resolution electron microscopy. Al₂CuMg precipitate improve the mechanical properties of the AlCu₁₅Mg₅ alloy because the precipitates act to impede dislocation motion through the material. The two alloys AlCu₁₅Mg₅, without of Ti and with 0.3%Ti, reveal a similar density of precipitate with a particle size ranging from 50nm up to 80nm in length. The precipitates have an irregular shape and precipitates in the [2 1 4] direction. The precipitates mainly composed of Al, Cu and Mg and homogeneously distributed throughout the matrix. Small-size particles and dislocations observed by TEM with EDS mapping showing the copper rich nature of particles. Al, Cu, Mg were detected by EDS, and EDS maps suggests that they correspond to Al₂CuMg.