Microstructures　and　mechanical　properties　of　the　Mg-4Y-2Gd-0.4Zr　alloy　with　Zn　additions　have　been　investigated.　The　investigation　suggests　that　the　mechanical　properties　of　the　alloys　have　been　greatly　improved　after　hot　extrusion　due　to　the　refinement　of　microstructures,　especially　the　elongations.　The　extruded　Mg-4Y-2Gd-1.0Zn-0.4Zr　alloy　displays　excellent　tensile　properties.　The　ultimate　tensile　strength　and　the　yield　tensile　strength　are　291　and　228　MPa,　respectively,　with　an　elongation　of　28%.　The　additions　of　Zn　have　an　obvious　effect　on　refining　microstructure　of　the　extruded　alloys,　and　the　vicker　hardness　increases　with　increasing　Zn　additions.　The　age　hardening　responses　of　the　extruded　alloys　have　been　investigated　at　220　degrees　C.　These　alloys　display　unobvious　ageing　hardness　responses.　(C)　2010　Elsevier　B.V.　All　rights　reserved.