The　hot　deformation　behavior　of　an　Al-5.7　wt.%Mg　alloy　with　erbium　was　studied　by　compressive　deformation　tests　in　the　strain　rate　range　of　0.001-10　s(-1)　and　temperature　range　of　300-500　degrees　C.　The　constitutive　equations　were　presented　considering　the　values　of　A　and　beta　as　a　function　of　strain　in　the　exponential　function　form.　The　error　of　predicted　and　measured　data　was　less　than　9%.　Dynamic　recrystallization　was　restrained　by　precipitate　with　Er　and　dynamic　recovery　dominated　in　the　hot　deformation.　The　mechanism　of　dynamic　recovery　was　dislocation　movement　and　the　development　of　microstructure　during　deformation　can　be　characterized　by　the　Z　parameter,　and　then　the　relationship　between　subgrains　and　deformation　parameters　have　been　also　established.　(C)　2009　Elsevier　B.V.　All　rights　reserved.