Effects of Ag content and heat treatment on the microstructure and properties of SLMed AZ61 Mg–Al–Zn alloy

The effects of Ag (0, 0.5, 1, and 2 wt%) content on the microstructure and mechanical properties of SLMed AZ61 Mg–Al–Zn alloy in the as-deposited and heat-treated conditions were investigated. The microstructure of SLMed AZ61 Mg–Al–Zn alloy is composed of α-Mg matrix and eutectic of α-Mg and Mg17Al12 phase at grain boundaries. The addition of Ag inhibited the growth of β-Mg17Al12 phase and further refined the grain size. After adding 2 wt% Ag, the volume fraction of β-Mg17Al12 phase is decreased from 40.53 to 30.27%, and the average grain diameter is decreased from 2.35 to 1.82 μm. Mg54Ag17 phase particles were formed after Ag was added and distributed in the grain boundary, which was beneficial to enhance the mechanical properties of Mg–Al alloy. After 8-h solution treatment at 420 °C β-Mg17Al12 phase was basically dissolved in α-Mg matrix, which was beneficial to the precipitation of discontinuous β phase during aging treatment, and this discontinuous β phase could effectively enhance the strength of Mg–Al alloy. When the content of Ag is 2 wt%, the mechanical properties and corrosion resistance of Mg–Al alloy are enhanced. After solution treatment, the mechanical properties of Mg–Al alloy are decreased, but the corrosion resistance is greatly enhanced. After aging treatment, the mechanical properties are increased, but the corrosion resistance is decreased.