Effects of direct aging on precipitation behavior, mechanical properties and thermal conductivity of an Mg-3Al-5Zn-3Ca alloy

This work reveals the precipitation behavior in an Mg-3Al-5Zn-3Ca alloy during isothermal aging (without prior solution treatment) and its effects on mechanical properties and thermal conductivity. Significant precipitation of micro-scale C15-Al ₂ Ca Laves phase occurs within the grains only when the temperature reaches 350 °C. During the initial aging stage, the precipitation fraction, number density, and size increase with aging time, while the solute-enriched zones near the grain boundary Ca-containing second phases are gradually consumed by nearby precipitation. Peak aging is achieved after 20 h. Upon further aging to 60 h, the volume fraction and average size of the precipitates continue to increase, exhibiting a balanced combination of properties. Dissolution of the grain boundary phases and precipitates occurred after 100 h.