In　this　paper,　long-term　thermal　treatment　of　a　binary　Ni-Al　model　nickel-based　superalloy　was　performed　at　1000　degrees　C　for　50　h,　100　h　and　200　h.　The　evolution　of　the　gamma/gamma＇　interface　was　studied.　As　the　treatment　time　increased,　the　gamma＇　precipitates　coarsened　and　grew.　Regular　interface　instability　was　observed　that　the　shape　of　the　gamma/gamma＇　interface　changed　from　flat　to　wavy.　This　interfacial　instability　was　caused　by　the　dynamic　balance　of　strain　energy　and　surface　energy　at　the　interface　between　the　two　phases.　In　addition,　secondary　gamma＇　precipitates　were　observed　after　long-term　treatment　and　some　of　the　larger　ones　took　on　pillow-like　shapes.　The　pillow-shaped　distortion　was　because　that　the　growth　rate　of　the　cube　vertices　was　faster　than　that　of　other　locations　due　to　the　different　strain　states　at　different　locations.　(C)　2015　Elsevier　B.V.　All　rights　reserved.