Effect of Al element on microstructure, mechanical properties and damping capacity of LPSO-containing Mg-Y-Zn-Li alloy

A novel LPSO containing Mg-5Y-2n-2Li-0.5Al alloy with superior mechanical behaviors and damping capacities was first developed in this paper. The microstructure evolution, mechanical and damping properties of Mg-5Y2n-2Li-0.5Al alloy were analyzed and compared with those of Mg-5Y-2Zn-2Li alloy. The results indicated the extruded Mg-5Y-2n-2Li-0.5Al alloy exhibited bimodal grain structure, including fine dynamically recrystallized grains (DRXed grains) and coarse un-dynamically recrystallized (unDRXed) grains, accompanied by the produce of the 14H LPSO phase, Al3(Y, Zn) particle and nano-precipitates AlLi phase. Due to the strengthening effects of grain boundary, residual dislocation and precipitation, the ultimate tensile strength (UTS), tension yield strength (TYS) and elongation (EL) of the extruded Mg-5Y-2Zn-2Li-0.5Al alloy were 312 MPa, 229 MPa and 10.9%, respectively, which were higher than that those of the extruded Mg-5Y-2Zn-2Li alloy. In addition, the extruded Mg-5Y-2Zn-2Li-0.5Al alloy displayed good damping capacities at both room and high temperature (RT and HT), and its RT damping value (Q-1) at 5 x 10-4 strain amplitude exceeded 0.01, which associated with a high density of movable dislocation. With rising the temperature, the extruded Mg-5Y-2n-2Li-0.5Al alloy possessed superior damping properties than the Al-free alloy, which derived from the grain boundary slide (GBS) and the activation of the incoherent interface between the Al3(Y, Zn) and alpha-Mg phase after adding Al element.