Complex precipitates with long periodic stacking (LPS) phase and precipitation behaviors in the Mg97Zn1Y1.5Nd0.5 alloy by age-annealing

We report the first microscopic observation of complex precipitates coexisting with LPS phases in Mg97Zn1Y1.5Nd0.5 (at %) alloy formed by aging at 473 K, and their effects on mechanical properties. It was found that the β’ [space group Cmc21 , a = 0.68 nm], β1[space group F m 3 ¯ m , a = 0.77 nm] phases and GP zones in α-Mg matrix are responsible for the peak hardness; which appeared after 30 h of annealing at 473 K, while large β1 precipitates and GP zones appeared in an over-aged specimen. With the increase of the annealing temperature from 473 K to 523 K, stacking faults, together with GP zones appeared. It is proposed that the precipitates and GP-zones contribute simultaneously to the age-hardening process, and that GP zones are more stable at 473 K than 523 K.