The　formation　of　intermetallic　compound　has　been　widely　considered　as　an　effective　strengthening　approach　in　Al　alloy.　Its　precipitate　dimension　is　a　key　factor　influencing　the　mechanical　performance.　Except　for　the　pinning　effect　of　nanosized　precipitate,　the　contribution　of　submicron　precipitate　is　also　nonnegligible.　Therefore,　establishing　the　mechanism　framework　for　the　relationship　of　manufacturing　process-precipitate　structure-fracture　performance　is　of　great　significance,　which　is　essential　and　foundational　for　optimizing　the　practical　service　performance　of　alloys　parts.　Herein,　by　taking　the　Al-Cu-Ni　series　alloy　(e.g.　RR350)　as　background,　the　study　reveals　the　microstructure　evolution　of　high-strength　submicron　Al7Cu4Ni　precipitate　from　fabrication　(additive　manufacturing-heat　treatment)　to　failure,　and　its　influence　mechanism　on　the　fracture　behavior.　Through　the　microstructure　regulation,　a　high　elongation　rate　of　∼28.5　%　and　slightly-deteriorated　ultimate　tensile　strength　of　∼305.2　MPa　are　achieved.　The　in-situ　and　ex-situ　characterizations　are　employed　to　analyze　the　synergy　mechanism　of　strength-ductility　performance.　Some　novel　findings　are　obtained　that　the　submicron　grain-boundary　precipitates　can　interrupt　the　intergranular　crack　by　influencing　the　stress　status,　thus　decreasing　the　crack　propagation　rate　and　altering　its　propagation　pathways.　The　entangled　dislocation　also　presents　an　obstruction　impact　on　the　intragranular　crack　extension　by　its　hardening　effect.　Moreover,　the　submicron　Al7Cu4Ni　precipitates　with　high　bonding　strength　can　withstand　the　concentrated　stress　to　maintain　a　stable　structure　during　alloy　fracture,　meanwhile　present　a　strengthening　effect　on　α-Al　matrix　to　ameliorate　the　deterioration　of　tensile　strength.　The　characterization　of　dislocation　and　microcrack　evolution,　provides　direct　evidence　to　the　mechanism　framework　above,　and　could　also　provide　insights　into　the　strength-ductility　coordination　for　other　Al　alloys.　©　2025　The　Authors