Formation of enclosed precipitates structure in a novel Mg-RE alloy to enhance high-temperature mechanical properties

Abstract

• The enclosed precipitates structure was constructed in GWN-1.5Ag alloy. • Ag alloying and heat treatment are effective methods for controlling precipitates. • Enclosed precipitates simultaneously block basal and non-basal dislocation slip. • High-temperature mechanical properties of the alloy were improved significantly. The influences of Ag addition and heat treatment on precipitates evolution and high-temperature mechanical properties of a novel Mg-6Gd-2Y-Nd-0.4Zn-0.5Zr (GWN) alloy were investigated. The addition of Ag induced the precipitation of basal γ '' phase and prismatic β ' phase simultaneously resulting in the formation of special enclosed precipitates structure. Compared with the alloy without Ag, the peak hardness increased by 8.9%, while the ultimate tensile strength, yield strength and elongation at 250 °C increased by 24.8%, 23.9% and 7.6%, respectively, by adding 1.5 wt% Ag. The enclosed precipitates structure can effectively block dislocation slip, which is the primary reason for enhancing mechanical properties. Hence, the construction of the special enclosed precipitates structure provides an effective approach for designing and developing heat-resistant Mg alloys for aerospace applications.