Microstructure and mechanical properties of Mg-Zn-Gd-based alloys strengthened with quasicrystal and Laves phase

One kind of Mg3.5Zn0.6Gd-based alloy strengthened with quasicrystals was designed,and the effect of alloying elements on microstructure and mechanical properties of as-cast Mg-Zn-Gd alloy at room temperature and elevated temperatures were studied. The results indicate that MgZnCu Laves phase,which coexists with quasicrystal at grain boundary,emerges with the addition of copper element in Mg-Zn-Gd alloy. The strength of alloys exhibits the parabola curve with the increase of copper content. The alloy with 1.5%(mole fraction) Cu shows better mechanical properties at room temperature:tensile strength 176 MPa,yield strength 176 MPa and elongation 6.5%. The existence of MgZnCu Laves phase can effectively improve the heat resistance and elevated temperature properties of the alloy. The alloy with 1.5% Cu has better mechanical properties at 200 ℃:tensile strength 130 MPa and elongation 18.5%. The creep test of the alloys at 200 ℃ and 50 MPa for 102 h indicates that Mg3.5Zn0.6Gd alloy reinforced with quasicrystal has better creep properties than AE42,which can be further improved with the introduction of Laves phase in the alloy.