Two　distinct　evolutionary　processes　of　secondary　gamma＇　precipitates　in　a　Ni-based　single　crystal　superalloy　were　revealed　by　means　of　Cs-corrected　high-resolution　transmission　electron　microscopy　(HRTEM)　and　corresponding　X-ray　energy　dispersive　spectroscopy　analyses.　Upon　creep　testing　at　elevated　temperatures,　it　was　determined　that　large　quantities　of　secondary　gamma＇　precipitates　were　formed.　The　precipitates　were　found　to　select　two　distinctive　forms　and　routes:　one　randomly　dispersed　in　the　gamma　matrix　(2nd　gamma＇(gamma)),　and　the　other　formed　at　nodes　of　dislocation　networks　(2nd　gamma＇(d))　in　regular　arrays.　These　two　types　of　secondary　gamma＇　precipitates　exhibited　different　evolutionary　morphologies　and　mechanisms.　The　2nd　gamma＇(gamma)　precipitates　progressively　evolved　in　shape　from　spherical　to　cuboidal　and　then　to　butterfly-like　shapes,　and　the　mean　size　also　increased　gradually　from　11　nm　to　34　nm.　The　2nd　gamma＇(d)　precipitates　exhibited　stable　cuboidal　morphology　and　a　mean　size　of　30　nm.　These　differences　are　attributable　to　the　different　element　transport　conditions　for　the　two　types　of　precipitates,　i.e.,　an　uphill　diffusion　for　the　2nd　gamma＇(gamma)　precipitates　and　a　dislocation　network　pipe　transportation　for　the　2nd　gamma＇(d)　precipitates.　The　2nd　gamma＇(gamma)　precipitates　show　severe　segregation　of　gamma＇-rich　elements　of　Ni　and　Al　and　deficiency　of　gamma＇-poor　elements　of　Cr　compared　with　the　2nd　gamma＇(d)　precipitates.　(C)　2016　Acta　Materialia　Inc.　Published　by　Elsevier　Ltd.　All　rights　reserved.