Abstract: Carbide dispersion reinforcing has been demonstrated to be an effective way of strengthening metal matrix composites. However, plagued by the nerve-wracking fact that the carbide particles tend to aggregate at the grain boundary of the metal matrix, grow up, and form an incoherent interface with it, their improvement in mechanical strength tends to be limited. In this study, spark plasma sintering (SPS) was used to prepare the bulk alloy Ni20Cr and its composites with different carbides including TiC, SiC, and Ti₃SiC₂. Plasma leads to discharge and elevates temperature at the interface to melt the Ni20Cr alloy particles locally. When cooled down, the alloy is heterogeneously solidified on the surface of the carbide and builds up a coherent interface with it. Owing to the decomposition of Ti₃SiC₂ during sintering, it completely transformed into nanosized TiC particles, which are engulfed by the outer melted layer of Ni20Cr and well dispersed within the alloy grains. In comparison to the Ni20Cr alloy, the composite with merely 4 wt% Ti₃SiC₂ gains over three times enhancement in yield strength to 879 MPa, while keeping a moderate high elongation of 17.8 %. Finite element analysis demonstrated that the combination of SPS and precursor MAX phase of Ti₃SiC₂, which results in the in-situ precipitation of coherent ultrafine TiC particles in alloy grains, plays the key role in getting a good balance between mechanical strength and ductility for the Ni20Cr matrix composites.

Key words: Metal matrix composites, Spark plasma sintering, Interfaces, Mechanical properties