Fabrication and characterization of NiTi/Ti3SiC2 and NiTi/Ti2AlC composites

Spark plasma sintering (SPS) was used as a fast consolidation technique to reduce reactions during powder consolidation of highly reactive systems (shape memory alloy/ternary carbide composites), which could not otherwise be fabricated using conventional methods. NiTi/Ti2AlC and NiTi/Ti3SiC2 powder mixtures, each with a 50/50 volume ratio, were processed in the 1233-1373 K temperature range under 100-300 MPa for 3 to 30 min. Martensitic phase transformation behavior of the composites was studied using differential scanning calorimetry and was compared with starting powders to evaluate the transformable NiTi in the composites. The effects of starting materials and processing conditions (sintering temperature, soaking time, and sintering pressure) on densification, reaction, and transformable NiTi were studied. A high-pressure (300 MPa) run at 1233 K for 8 min produced a fully-dense NiTi/Ti3SiC2 composite with a maximum percent of transformable NiTi. Based on the phase analysis on the interfacial reaction layers, we developed the reaction mechanisms between NiTi and Ti3SiC2 or Ti2AlC during SPS. The results suggest that SPS is a viable technique to fabricate highly reactive ceramic-metal system with active components.