Effects of Solute Atoms Re-Dissolution on Precipitation Behaviour and Mechanical Properties of Selective Laser Melted Al-Mg-Sc-Zr Alloys

Abstract

Although Al-Mg-Sc-Zr alloy manufactured by selective laser melting (SLM) technology has attracted extensive attention, nevertheless, it often requires a post-processing for practical use. Notably, the effects of the different post heat treatments on the SLM Al-Mg-Sc-Zr alloy have not been clearly elucidated. Hence, a series of different heat treatments including aging treatment, solution treatment and solution-aging treatment were designed to improve the mechanical properties of the SLM samples. Furthermore, the impacts of different heat treatment regime on the phase transitions, microstructural evolutions and mechanical properties of SLM specimens were systematically investigated in this study. Scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM) were used to carefully study the emergence and effects of Al 3 (Sc, Zr) precipitates. The cubic primary Al 3 (Sc, Zr) particles with a size of ~100 nm were formed during the SLM. Besides, plenty of spherical secondary Al 3 (Sc, Zr) precipitates would be appeared after aging treatments, greatly enhancing the mechanical properties of the SLM Al-Mg-Sc-Zr alloy. Compared to other states, the aged samples were demonstrated to exhibit the highest mechanical properties. Benefiting from the grain boundary strengthening and precipitation dispersion strengthening mechanisms, ultimate tensile strength of the aged samples increasing from 353.7 MPa to 528.0 MPa.

Keywords: Selective laser melting, Al-Mg-Sc-Zr alloy, Heat treatment regime, Precipitation behavior, mechanical properties