Influence of Long-Period-Stacking Ordered Structure on the Damping Capacities and Mechanical Properties of Mg-Zn-Y-Mn As-Cast Alloys

Abstract

Magnesium alloys are concerned for its mechanical properties and high damping performance. The influence of Mn toward the internal organization morphology of long-period stacking ordered (LPSO) second phase and the consistent damping performance in Mg-4.9Zn-8.9Y-xMn have been studies in this work. It has shown that the addition of Mn tends to diffuse to the LPSO interface and causes the LPSO phase to expand in the arc direction. The circular structure of LPSO can optimize the damping property of the alloy better than the structure with strong orientation, especially at the strain of 10−3 and 250 °C. With more additions of Mn, damping would have a reduction due to the dispersed fine LPSO phases and α-Mn particles. When the Mn content is higher than 1.02%, the grain is refined, and mechanical properties have been significantly improved. Mg-4.9%Zn-8.9%Y-1.33%Mn shows the best mechanical property.

Effects of heat treatment routes on microstructure and damping properties of Mg–Zn–Y–Mn alloys

“…amount and refinement). With the addition of Mn content, the mechanical changes of the samples in the three states are relatively consistent, showing a monotonic upward trend, which is related to the fine grain strengthening of Mn and the refinement of the LPSO phase [9].…”

“…In Mg-Zn-Y-Mn alloys, both LPSO phases and α-Mn particles have obvious effects on dislocations' slipping, leading to complicated internal friction. According to a previous study [7,9], as-cast Mg-Mn alloys present high strain-dependent damping values. Mn could provide long dislocation into the alloys, which can be explained using the Granato-Lücke dislocation damping theory [18,19].…”

“…Table 1 lists the nominal and actual chemical composition. The previous study [9,12] found that the LPSO phase in Mg-Zn-Y alloy has high temperature stability, and its dissolution temperature is about 547 °C. It was found that the LPSO phase with rod-like structure can be obtained after heat treatment at 540 °C for 4 h. In this experiment, 540 °C and 550 °C were selected as the experimental temperature to analyze the effect of Mn on the structure of LPSO during heat treatment.…”

“…It can be found that the Y/Zn ratio in the second phase (point A) at the grain boundary is about 1.53. In combination with previous studies [9][10][11][12], the LPSO phase can be determined. Compared with as-cast alloys, the net-shaped LPSO phase at the grain boundary in alloy I am transformed into rod or small block, with some white Y-rich particles (point B) attached on it.…”

“…LPSO phase is a hot spot in the research of magnesium alloys. In the study of the influence of LPSO on the damping of magnesium alloy [8][9][10][11], it is found that the mechanical properties and damping properties were improved with the increase of LPSO content. In addition, the microstructure of LPSO phase in magnesium alloy can be changed by heat treatment to improve the damping and mechanical properties of the alloy.…”