Microstructure　and　mechanical　properties　development　of　extruded　Mg-1Y　(wt.　%)　binary　alloy　during　equal　channel　angular　pressing　(ECAP)　with　route　Bc　at　400　degrees　C,　and　subsequent　annealing　treatment　between　300-400　degrees　C　at　different　holding　time　of　5-120　min　were　investigated　using　an　optical　and　scanning　electron　microscope　(SEM),　electron　back　scattered　diffraction　(EBSD),　tensile　test,　and　hardness　test.　The　grain　size　of　as-extruded　material　(similar　to　10.9　mu　m)　was　refined　significantly　by　1-pass　ECAP　(similar　to　5.8　mu　m),　and　resulted　in　a　remarkably　enhanced　elongation　to　failure　(EL)　(similar　to+62%)　with　a　slightly　decreased　ultimate　tensile　strength　(UTS)　(similar　to-3%)　comparing　to　the　as-extruded　condition　(EL　=　11.3%,　UTS　=　200　MPa).　The　EL　was　further　increased　to　27.3%　(similar　to+142%)　after　four　passes　of　ECAP　comparing　to　the　as-extruded　condition,　which　was　mainly　caused　by　the　much　more　homogenized　microstructure.　The　split　basal　poles　with　about　60　degrees　rotations　to　the　extruded　direction　(ED),　the　relatively　coarsened　grain　size　by　static　recrystallization　(SRX)　and　post-dynamic　recrystallization　(PDRX)　after　four　passes　of　ECAP　might　be　responsible　for　the　decreased　strength　with　increasing　ECAP　pass.　During　the　annealing　treatment,　recovery　dominantly　occurred　at　300　degrees　C,　SRX　and　grain　growth　emerged　at　350　degrees　C　and　400　degrees　C,　respectively.　Meanwhile,　the　grain　grew　and　hardness　decreased　rapidly　even　within　5　min　for　1-pass　ECAPed　material　at　400　degrees　C,　indicating　a　larger　grain　boundary　mobility　of　ECAPed　materials　induced　by　higher　deformation　energy　than　the　as-extruded　ones.