Effect of quasicrystal phase on mechanical properties and damping capacities of Mg-Zn-Y-Zr alloys

Four Mg-5x%Zn-x%Y-0.6%Zr alloys reinforced with the I-Mg3YZn6 quasicrystal phase were fabricated by introducing Zn and Y elements into Mg-0.6%Zr alloys under conventional solidification condition. Due to the coherent lattice relationship between the I-Mg3YZn6 phase and the α-Mg matrix, the grain sizes of the Mg-Zn-Y-Zr alloys are obviously refined and the tensile strengths are largely improved to a maximum value of 216 MPa. The fracture mechanism transformed from cleavage fracture to quasi-cleavage fracture with increasing amount of I-Mg3YZn6 phase. The damping capacities of the Mg-Zn-Y-Zr alloys decrease with the increasing I-Mg3YZn6 phase and the damping behavior can be explained with the G-L dislocation model. The forming of the I-Mg3YZn6 phase makes more grain boundaries, phases and interfaces generate in the alloys. And the dislocation densities in the alloys hardly changes as little residual stress or entanglement of dislocation generates at the interface between the I-Mg3YZn6 phase and the α-Mg matrix. So the damping values are reduced accordingly with the strong pinning points on dislocations increasing tremendously.