Effect of Y addition on microstructure and mechanical properties of Mg-Zn-Mn alloy

The effects of Y on the microstructure and mechanical properties of Mg-6Zn-1Mn alloy were investigated. The results show that the addition of Y has significant effect on the phase composition, microstructure and mechanical properties of Mg-6Zn-1Mn alloy. Varied phases compositions, including Mg7Zn3, I-phase (Mg3YZn6), W-phase (Mg3Y2Zn3) and X-phase (Mg12YZn), are obtained by adjusting the Zn to Y mass ratio. Mn element exists as the fine Mn particles, which are well distributed in the alloy. Thermal analysis and microstructure observation reveal that the phase stability follows the trend of X>W>I>Mg7Zn3. In addition, Y can improve the mechanical properties of Mg-Zn-Mn alloy significantly, and the alloy with Y content of 6.09% has the best mechanical properties. The high strength is mainly due to the strengthening by the grain size refinement, dispersion strengthening by fine Mn particles, and introduction of the Mg-Zn-Y ternary phases.