The　effect　of　Yb　and　Si　on　precipitation　hardening　and　recrystallization　of　Al-Zr　alloys　have　been　investigated.　The　results　show　that　Yb　is　more　effective　than　Si　to　accelerate　the　precipitation　kinetics　and　stimulate　the　precipitation　of　Al-Zr　alloy.　The　peak　hardness　values　for　the　Al-Yb-Si-0.08Zr　are　510　MPa　and　515　MPa　after　isochronal　aging　to　425　degrees　C　and　isothermal　at　350　degrees　C　for　200　h,　respectively,　which　are　significantly　larger　than　that　of　the　Al-Yb-Zr　and　Al-Si-Zr　alloys.　The　precipitates　in　alloys　with　addition　of　Zr　are　more　thermally　stable　than　that　of　the　Al-Yb　alloy.　The　recrystallization　temperatures　of　Al-Zr,　Al-Si-Zr,　Al-Yb-Zr　and　Al-Yb-Si-Zr　alloys　are　250,　400,　425　and　450　degrees　C,　respectively,　increase　with　the　increase　of　the　corresponding　peak　aging　hardness.　The　recrystallization　temperature　of　Al-Yb　alloy　is　325　degrees　C,　which　is　much　lower　than　that　of　the　Al-Yb-Zr　alloy　due　to　the　coarsening　of　the　Al3Yb　at　temperature　larger　than　300　degrees　C.　(C)　2014　Elsevier　B.　V.　All　rights　reserved.