In-situ synchrotron X-ray diffraction study of the precipitates-matrix interaction in a selective laser melted Al-Mg-Sc-Zr alloy

Abstract

In-situ synchrotron diffraction analysis was employed to investigate the influence of precipitates on the deformation of an Al-Mg-Sc-Zr alloy fabricated through selective laser melting. The evolution of lattice strain, dislocation density, and dislocation types throughout the tensile test exhibits three distinct stages. In the elastic region, the precipitates and the matrix exhibit identical lattice strains. Upon yielding, the discrepancy in lattice strain between the matrix and precipitates widens, resulting in important dislocation pile-up and a sharp increase of dislocation density. The variation in lattice strain, peak broadening and dislocation density reveals that the plasticity is firstly accumulated by the matrix and then by the precipitates after yielding. Furthermore, the portion of screw-type dislocations gradually became dominant during plastic deformation. This is attributed to the favored cross-slip motion related to the shearing of nanosized precipitates and the alleviation of the solute drag on edge-type dislocations.