Impact of hot rolling on the mechanical characteristics and microstructure of copper-based metal matrix composites reinforced with titanium carbide

Copper-based metal matrix composites reinforced with varying weight percentages (0, 2, 5, 7, and 10 wt%) of powdered titanium carbide (TiC) particles were successfully fabricated using stir casting, followed by hot rolling as a secondary processing route to enhance their mechanical performance. The microstructural evolution, phase characteristics, and mechanical behaviour of both as-cast and hot-rolled composites were systematically studied. Microstructural examination revealed a dendritic grain structure with non-uniform grain size distribution in as-cast composites, whereas hot-rolled composites exhibited a refined lath-shaped grain structure with uniform TiC particle distribution, attributed to the plastic deformation induced during rolling. XRD analysis confirmed the presence of high-intensity copper matrix peaks in hot-rolled composites and relatively stronger TiC peaks in as-cast composites due to the fragmentation of coarse reinforcement particles during rolling. Mechanical testing demonstrated that hot rolling significantly enhanced both hardness and tensile strength compared to the as-cast condition. The Brinell hardness of the hot-rolled Cu-10 wt% TiC composite reached 59.54 BHN, representing a 42.1% improvement over as-cast pure copper (41.9 BHN). Similarly, the ultimate tensile strength (UTS) of the hot-rolled Cu-10 wt% TiC composite achieved 182.5 MPa, corresponding to a 50.3% improvement over as-cast pure copper (121.4 MPa). However, ductility decreased progressively with increasing TiC content and hot rolling, from 71.56% in as-cast pure copper to 48.69% in hot-rolled Cu-10 wt% TiC, owing to strain hardening effects and grain boundary restriction by TiC particles. The optimal combined strength-ductility balance, assessed through the strain hardening parameter (UTS × % elongation), was achieved at 5 wt% TiC reinforcement in both as-cast and hot-rolled conditions. Fractographic analysis revealed a progressive transition from ductile dimple fracture to mixed-mode and predominantly brittle fracture with increasing TiC content, consistent with the observed mechanical trends.