To overcome the mechanical limitations hindering die-cast magnesium alloys, rare earth microalloying serves as a promising and economical strengthening approach. Mg-4Al-1.5La-2.5Ce-0.3Mn- x Y ( x = 0, 0.05, 0.1, 0.2) alloys with trace Y additions were fabricated via the high-pressure die-casting (HPDC) process. Following T5 aging treatment, high-temperature tensile tests were conducted on the alloys at 200 °C. The alloy with a Y addition of 0.2 wt.% exhibited the optimal high-temperature mechanical properties, achieving an ultimate tensile strength (UTS) of 140 MPa, a yield strength (YS) of 122 MPa, and an elongation (EL) of 27.7%, respectively. The incorporation of Y increased the content of precipitates and facilitated the formation of fine, continuous intragranular precipitates. The continuous intragranular precipitates could partition the matrix grains, restrict the slip space of dislocations within the grains, and thus contribute to the enhancement of alloy strength. The strength improvement of the alloys could be attributed to the combined effects of second-phase strengthening and grain refinement induced by the increased content and optimized distribution of precipitates, while the improvement in plasticity originated from the effective promotion of pyramidal slip activation by Y element.
Qin et al. (Wed,) studied this question.