Samples　made　of　a　super　high　strength　aluminum　alloy　with　high　Zn　content　were　friction　stir　welded　with　rotation　rates　of　350-950　rpm　and　welding　speeds　of　50-150　mm/min.　The　effect　of　welding　parameters　on　the　microstructure　and　mechanical　properties　was　investigated.　It　was　observed　that　the　grain　size　of　the　nugget　zones　decreased　with　the　increasing　welding　speed　or　the　decreasing　tool　rotation　rate.　Most　of　the　strengthening　precipitates　in　the　nugget　zone　were　dissolved　back　and　the　intragranular　and　grain　boundary　precipitates　in　the　heat　affected　zone　coarsened　significantly.　The　greatest　ultimate　tensile　strength　of　484　MPa　and　largest　elongation　of　9.4　were　obtained　at　350　rpm　-100　mm/min　and　350　rpm　-50　mm/min,　respectively.　The　ultimate　tensile　strength　and　elongation　deteriorated　drastically　when　rotation　rate　increased　from　350　to　950　rpm　at　a　constant　welding　speed　of　100　mm/min.　(C)　2014　Elsevier　Ltd.　All　rights　reserved.