Combustion synthesis and thermal stress analysis of TiC-Ni functionally graded materials

Simultaneous combustion synthesis reaction and compaction of Ti, C, and Ni powders under a hydrostatic pressure was carried out to fabricate dense TiC-Ni functionally graded materials (FGMs) in a single processing operation. Scanning-electron microscope (SEM) and microprobe analysis (EPMA) was employed to investigate the microstructure and composition distribution. Experimental results demonstrate that Ni and Ti composition varies continuously and gradually along the thickness of the reacted sample, remarkably different from stepwise type prior to combustion synthesis. The constituents are continuous in microstructure everywhere and no distinct interaction occurs in TiC-Ni FGM. Moreover, the thermal physical and mechanical properties were measured as a function of composition. It was found that the properties of the FGMs were dependent on Ni content. The residual thermal stress of TiC-Ni FGM and dual-laminate non-FGM cooled to room temperature after combustion synthesis has been analyzed by finite element method. TiC-Ni FGM shows distortion and thermal stress relaxation, which is in striking contrast to the layered TiC-Ni non-FGM.