Effect of extrusion parameters on microstructure, mechanical properties and damping capacities of Mg-Y-Zn-Zr alloy

In this work, different extrusion processes were carried out on a Mg-3.16Y-1.85Zn-0.37Zr (wt%) alloy containing long period stacking ordered (LPSO) phases. The effect of extrusion parameters on the microstructure, mechanical properties and damping capacities of the alloy were investigated. The results show that the alloy extruded at 360 °C and a ratio of 9:1 shows good comprehensive properties with a tensile yield strength (TYS) of 280 MPa, ultimate tensile strength (UTS) of 330 MPa, elongation (EL) to failure of 21% and damping value Q−1 of 0.023 (strain amplitude ε = 10−3) at room temperature (RT). As the extrusion temperature or ratio increases, the strength decreases and EL increases, while the damping value of ε = 10−3 at RT is slightly down due to the decrease in the LPSO phase and dislocation density. All as-extruded alloys show a similar variation tendency for the relationship between Q−1 and test temperature T, with elevated temperature (ET) damping capacities Q−1 > 0.01 at a frequency of 1 Hz and T > 300 °C. Strengthening mechanisms for mechanical properties of the as-extruded alloys have also been analyzed, and the damping capacities are also discussed in terms of the Granato-Lücke (G-L) dislocation theory and grain boundary sliding. The results of the present work provide a new perspective for further developing high-performance Mg-Y-based alloys with both high damping and excellent comprehensive mechanical properties by careful tailoring of the extrusion process parameters.