Effect of heat treatment on the microstructure and mechanical properties of Er-containing Al–7Si–0.6 Mg alloy by laser powder bed fusion

The Al–7Si–0.6 Mg alloy with added rare earth erbium (Er) was prepared by laser powder bed fusion (LPBF) technology, and the effect of heat treatment on the microstructure and mechanical properties was studied. The addition of Er introduces Al3Er to the molten pool, which can effectively hinder the epitaxial growth of the columnar crystal. The effect of rapid cooling and the addition of Er can also modify eutectic Si particles, resulting in an ultrafine eutectic network cellular structure. Moreover, the as-built samples have an excellent tensile strength exceeding 438 MPa and a ductility of over 8%; furthermore, such excellent mechanical properties are associated with small grains, a continuous Si network, and extremely oversaturated solid solubility. After heat treatment, LPBF-processed alloy samples exhibit superior mechanical properties, especially after direct age treatment, which can mainly be attributed to the precipitation strengthening effect introduced by nanosized precipitates.