Microstructure and mechanical properties of TiC-Ni functionally graded materials by simultaneous combustion synthesis and compaction

The simultaneous combustion synthesis and hot compaction of Ti, C and Ni powders under a hydrostatic pressure was undertaken to fabricate fully dense TiC-Ni functionally graded materials (FGM) in a single processing operation. The composition gradient was optimized by finite element analysis and obtained by stacking different powder mixtures of desired compositions. X-ray diffraction, scanning electron microscopy and microprobe analysis were employed to investigate the crystalline phase, microstructure and Ni distribution. Experimental results demonstrate that the combustion reaction was complete and the final products contained the phases TiC and Ni only, the microstructure varies coherently throughout the specimen with no distinct interface. The physical and mechanical properties were measured as a function of composition. It was found that the properties of the FGMs were dependent on the Ni content and approached the maximum values for the relative density, hardness and flexural strength at room temperature when the Ni content was increased to 20 wt%. The maximum in fracture toughness value was found in the TiC-30 wt% Ni material. (C) 2000 Kluwer Academic Publishers.