Separating densification and in-situ reaction of Cu–Ni and B4C system for tailoring properties of resulting composites

A novel two-step sintering strategy is developed for the Cu-Ni+B 4 C system, separating the densification and in-situ reaction stages, to fabricate (Ni 2 B+C)/Cu composites. In the first step, the Cu-Ni+B 4 C powder mixture is rapidly densified into compacted blocks via hot-pressing sintering. In the second step, these blocks are transferred to a pressure-less sintering furnace to promote the in-situ reaction between Ni and B 4 C. Experimental studies were conducted on the densification and in-situ reaction processes, as well as the properties of the resulting composites. Kinetic analysis revealed that the two-step sintering strategy effectively enhances densification and provides precise control over the size and distribution of the reinforcing phase. Compared to the traditional one-step hot-pressing sintering, the composites fabricated using the two-step strategy exhibit significant improvements of 15.4% in tensile strength, 15.0% in fracture elongation, 13.4% in hardness, and 13.1% in electrical conductivity. The in-situ reaction of Cu-Ni+B 4 C system is predominantly governed by interface control, with an activation energy of 76.7 kJ/mol, which is higher than that of traditional age-hardening alloys. Future research should focus on exploring methods to reduce the reaction activation energy of this system. The two-step sintering strategy holds promise as an effective method for large-scale industrial production of in-situ composites.