Structure Determination of Al2CuMg Precipitates in AlCu15Mg5 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.