The synthesis of porous TiC-TiB2-NiAl composites by SHS

Porous TiC-TiB2-NiAl composites have been prepared through self-propagating high-temperature synthesis (SHS) of 3Ti + B4C + x(Ni+Al) -> TiC + 2TiB(2) + xNiAl using Ni, Al, Ti, B4C powders as raw materials. The effects of Ni and Al content on phase constitution and pore structure of the obtained porous TiC-TiB2-NiAl composites have been investigated. XRD results show that the final composites of Ti+B4C+Ni+Al powders consist of TiC, TiB2 and NiAl, while only TiC and TiB2 are observed without using Ni+Al powders in the reaction system. NiAl additives play a significant role in controlling reaction behavior and constituents of the final products. TiC, TiB2 and NiAl are homogenously distributed in porous TiC-TiB2-NiAl composites, and TiC shows spherical. shape, TiB2 exhibits hexagon or long strip shape while NiAl shows the irregular shape distributed between TiB2 and TiC particles. The prepared TiC-TiB2-NiAl composites contain a large amount of pores with the aperture concentrating between 20-80 mu m and the porosity was about 35%, NiAl additives make the pores distributed uniformly in the matrix. The more NiAl additives, the more obvious of melting trace on the matrix skeleton, some spherical particles adhering on pore wall gradually submerge in matrix and combine with it closely. The NiAl additives increase the compressive strength of TiC-TiB2 and for TiC-TiB2-NiAl composites, the fracture mode of TiB2 and TiC is brittle fracture, while NiAl mainly occur transgranular fracture.