Ultrafine　β　grain　structures　with　recrystallized　morphologies　were　fabricated　by　severe　plastic　deformation　and　subsequent　annealing　in　Ti-10Mo-8　V-1Fe-3.5Al　alloy.　The　minimum　mean　β　grain　size　of　480　nm　was　obtained　for　the　first　time　as　a　recrystallized　structure　in　Ti　alloys.　Precipitation　behavior　of　α　in　subsequent　aging　significantly　changed　with　decreasing　the　recrystallized　β　grain　size.　Both　tensile　strength　and　total　ductility　of　the　aged　Ti-alloy　were　increased　by　the　β　grain　refinement.　Tensile　strength　of　1.6　GPa　and　total　elongation　of　9.1%　were　achieved　in　the　aged　specimen　having　the　prior　β　grain　size　of　480　nm,　which　was　attributed　to　its　finer　and　more　homogeneous　precipitated　microstructure　having　a　mixture　of　nanoscale　thin-plate　α　and　globular　α　without　side　α　plates　along　β　grain　boundaries.　©　2020　The　Authors