The　immiscible　bimetallic　composites　play　an　important　role　in　civilian　industries　and　aerospace　fields　owing　to　their　integrated　mechanical　and　physical　properties.　However,　metallic　composites　of　immiscible　constituents　suffer　from　one　critical　drawback　of　weak　interface　bonding,　which　makes　the　composites　particularly　vulnerable　at　elevated　service　temperatures.　Here　we　proposed　a　novel　strategy　to　resolve　the　challenge　by　creating　low-energy　phase　interfaces　in　a　typical　immiscible　bimetallic　W–Cu　composite.　This　was　achieved　by　in-situ　reactions　of　WO3　and　CuO　with　WC,　which　acts　in　a　dual　function　as　the　reducing　agent　for　the　reactions　and　an　interface　forming　agent.　The　sintered　W-WC-Cu　composite　possessed　a　significant　number　of　low-energy　WC/W　and　WC/Cu　interfaces　and　exhibited　a　compressive　strength　of　609　MPa　and　a　compressive　ductility　of　22.6　%　at　600　°C,　which　ranks　among　the　highest　in　similar　composites.　The　characteristics　of　WC/W　and　WC/Cu　interfaces　and　their　effects　on　the　mechanical　behavior　of　the　composite　were　demonstrated　by　the　timely　and　atomic-resolved　high-temperature　mechanical　investigations.　The　introduced　stable　interfaces　were　also　found　to　induce　[1‾　11]BCC　→　[011]FCC　phase　transformation　of　W　as　another　mechanism　of　plastic　deformation　in　addition　to　dislocation　activities　in　W　and　Cu.　This　study　provides　a　new　approach　to　greatly　enhance　the　mechanical　properties　of　the　immiscible　metallic　composites.　©　2024　Elsevier　Ltd