Microstructure, tensile properties and creep behaviors of as-cast Mg–2Al–1Zn–xGd (x = 1, 2, 3, and 4 wt.%) alloys

The microstructure, tensile properties and creep behaviors of as-cast Mg–2Al–1Zn–xGd (x = 1, 2, 3, and 4 wt.%) alloys have been investigated. The results indicated that the addition of Gd led to the formation of a branched (Mg, Al)3Gd phase and a cubic Al2Gd phase. The tensile properties of the AZ21 alloy have been improved greatly at both room temperature and elevated temperature due to the presence of the branched (Mg, Al)3Gd phase. The AZ21 alloy containing 4% Gd presented a good creep-resistant property. The steady-region and the total creep strain of the alloy after 100 h were 2.6 × 10−8 s−1 and 1.2%, respectively. The enhancement of creep properties of the AZ21 alloy was mainly ascribed to the thermal stable branched (Mg, Al)3Gd phase by which the movement of dislocations were impeded effectively.

► The as-casting Mg–2Al–1Zn–xGd (x = 1, 2, 3, and 4 wt.%) alloys are composed of α-Mg with zinc in solid solution, reticular (Al, Mg)3Gd phases and cubic Al2Gd phase.
► The heat resistant of the as-cast Mg–2Al–1Zn–xGd (x = 1, 2, 3, and 4 wt.%) alloys at 200 °C could be obviously improved with the increase of Gd content.
► The reticular (Mg, Al)3Gd phase improved the creep resistance due to the effect of barriers to dislocation movement.