An icosahedral Mg_3 YZn_6 quasicrystalline phase can be produced in Mg-Zn-Y system alloys when a proper amount of Zn and Y is contained,and it is feasible to prepare the quasicrystal phase-reinforced low-density magnesium alloy.In this article,phase con- stituents and the effect of reciprocating extrusion on microstructures and properties of the as-cast Mg-6.4Zn-1.1Y alloy are analyzed.The microstructure of the as-cast Mg-6.4Zn-1.1 Y alloy consists of theα-Mg solid solution,icosahedral Mg_3 YZn_6 qua- sicrystal,and Mg_3 Y_2Zn_3 and MgZn_2 compounds.After the alloy was reciprocatingly extruded for four passes,grains were refined,Mg_3 Y_2 Zn_3 and MgZn_2 phases dissolved into the matrix,whereas,Mg3 YZn6 precipitated and distributed uniformly.The alloy possesses the best performance at this state;the tensile strength,yield strength,and elongation are 323.4 MPa.258.2 MPa,and 19.7%,respectively.In comparison with that of the as-cast alloy,the tensile strength,yield strength,and elongation of the reciprocatingly extruded alloy increase by 258.3%,397.5%,and 18 times,respectively. It is concluded that reciprocating extrusion can substantially improve the properties of the as-cast Mg-6.4Zn-1.1 Y alloy,particularly for elongation.The high performance of the Mg-6.4Zn-1.1 Y alloy after reciprocating extrusion can be attributed to dispersion strenqtheninq and grain-refined microstructures. An icosahedral Mg_3 YZn_6 quasicrystalline phase can be produced in Mg-Zn-Y system alloys when a proper amount of Zn and Y is contained, and it is feasible to prepare the quasicrystal phase-reinforced low-density magnesium alloy. In this article, phase con- stituents and the effect of reciprocating extrusion on microstructures and properties of the as-cast Mg-6.4Zn-1.1Y alloy are analyzed. The microstructure of the as-cast Mg-6.4Zn-1.1 Y alloy consists of α-Mg solid solution, icosahedral Mg_3 YZn_6 qua- sicrystal, and Mg_3 Y_2Zn_3 and MgZn_2 compounds. After the alloy was reciprocatingly extruded for four passes, grains were refined, Mg_3 Y_2 Zn_3 and MgZn_2 phases dissolved in the matrix, while, Mg_3 YZn_6 precipitated and distributed uniformly. The alloy possesses the best performance at this state; the tensile strength, yield strength, and elongation are 323.4 MPa. 258.2 MPa, and 19.7%, respectively. In contrast with that of as-cast alloy, the tensile strength, yield strength, and elongation of the reciprocatingly extruded alloy increase by 258.3%, 397.5%, and 18 times, respectively. It is said that reciprocating extrusion can substantially improve the properties of the as-cast Mg-6.4Zn-1.1 Y alloy, particularly for elongation. performance of the Mg-6.4Zn-1.1 Y alloy after reciprocating extrusion can be attributed to dispersion strenqtheninq and grain-refined microstructures.