In　our　research,　the　effects　of　rare-earth　element　erbium　(Er)　on　microstructures　and　mechanical　properties　of　some　aluminum　alloys　are　investigated.　It　is　shown　that　aluminum　alloys　with　Er　additions,　including　Al-Mg,　Al-Zn-Mg,　Al-Zn-Mg-Cu,　1420　Al-Li　alloys　and　high　purity　aluminum,　have　refined　grain　size,　superior　thermal　stability,　and　higher　hardness　or　tensile　strength　with　unchanged　ductility.　It　is　concluded　that,　in　most　aluminum　alloys,　Er　Is　an　effective　alloying　element.　©　Institute　of　Materials　Engineering　Australasia　Ltd.