Guangli Bi

Microstructural evolution and age-hardening behavior of quasicrystal-reinforced Mg–Dy–Zn alloy

Microstructural evolution and age-hardening behavior of Mg–2Dy–6Zn (at%) alloy during solid-solution and aging treatment were investigated. The microstructure of as-cast alloy is composed of α-Mg, Mg3DyZn6 (I) phase, Mg3Dy2Zn3 (W) phase, Mg(Zn,Dy) phase and a small amount of Mg0.97Zn0.03 phases. After solid-solution treatment (480xa0°C, 12xa0h), all the I phases and most W phases dissolve into α-Mg matrix and the remainder W phases transform into Mg(Dy,Zn) phase and MgDy3 phase. During aging treatment, I phase and small amounts of W phases co-precipitate from α-Mg matrix, respectively. The alloy exhibits a peak hardness of HV 77.5 at 200xa0°C for 8xa0h. The excellent age-hardening behavior of alloy is mainly attributed to the co-precipitation strengthening of I and W phases.

Microstructural evolution and high-temperature compressive properties of an extruded Mg–Dy–Zn alloy sheet

Abstract Microstructural evolution and compressive properties of an extruded Mg-2Dy-0.5Zn (at.%) alloy sheet at 350°C were investigated. As the compressive strain increased, the volume fraction of dynamic recrystallization increased, the fine lamellar 14H long period stacking ordered phase precipitated in the dynamic recrystallization grain, and the Mg12ZnDy phase with an 18R long period stacking ordered structure gradually bent. These secondary phases not only acted as nucleation sites to promote dynamic recrystallization but also restrained grain growth by inhibiting dislocation movement and grain boundary sliding. The compressive yield strength, ultimate compressive strength, and compressive strain of the alloy sheet were 161 MPa, 212 MPa, and 12.4% at 350°C, respectively. The high compressive strengths were mainly attributed to grain refinement, kink band strengthening of the 18R long period stacking ordered phase and precipitation strengthening of the fine lamellar 14H long period stacking ordered phase in the dynamic recrystallization grain.