Effects of Mn addition on the microstructures and mechanical properties of the Mg-15Gd-1Zn alloy

The effects of different manganese (Mn) content of 0-0.8 wt% on the microstructures and roomtemperature tensile properties of Mg-15Gd-1Zn (wt%) alloys have been investigated. The results reveal that the solution-treated microstructures of the alloys are mainly composed of a-Mg matrix, the secondary eutectic phase [(Mg, Zn) Gd-3], X phase with 14H long period stacking ordered (LPSO) structure. However, small alpha-Mn particles precipitate within the a-Mg matrix with the increase of Mn content from 0 to 0.8 wt% during the solution treatment at 773 K. It shows that the a-Mn particles can inhibit grain growth, which can result in grain refinement. Moreover, Mn addition can promote the formation of 14H-LPSO structure in the solution-treated alloy by increasing stacking fault probability of a-Mg matrix. In this study, the influence mechanisms of Mn addition were suggested according to observation of microstructure and calculation of stacking fault probability. Besides, the room-temperature tensile properties can be improved as Mn addition content increases. In conclusion, the solution-treated Mg15Gd-1Zn-0.8Mn (wt%) alloy exhibits an ultimate tensile strength of 275 MPa, a yield strength of 154 MPa and an elongation of 7.4%. (C) 2016 Elsevier B.V. All rights reserved.