Wettability And Preparation Of Ni₃Al/TiC System Composite Materials

In the present paper, densified Ni3Al/TiC system composite materials with different compositions were prepared, in order that they could be used as the innermost wall of thermonuclear reactors, a kind of functionally graded material.Fine Ni3Al powders with an average grain size of 6.1 m were firstly prepared by SHS method and mechanical grinding for 36ks with the ratio of ball to powder at 3.5. The effects of grinding condition and heat treatment technique on the morphology, microstructure and composition as well as crystal structure of the prepared Ni3Al powders were discussed. The analysis of the grinding mechanism showed that the fineness of Ni3Al powders was caused by the breakage of large Ni3Al particles and grain boundaries between microcrystallines.The wettability between Ni3Al and TiC was measured by high temperature microscope, and then the effect of Mo addition on the wettability of Ni3Al/TiC and the mechanism of interface reaction were mainly discussed. The results showed that the wettability was further improved when 5wt% Mo was added and the wetting angle was only 11 . It was considered that, the substituted Ti reacted with Ni3Al in-situ and a layer of Mo solid solution was formed around the TiC particles, which decreased the solid-liquid surface tension between Ni3Al-TiC, leading to the decreasing of wetting angle.By adding proper content (1~5vol%) of Cr3C2, TiC and Ni3Al/TiC composites were densified at a low temperature and the growth of TiC crystal was restrained simultaneously by the solid reaction of TiC-Cr3C2 binary system. Finally, by adding 3vol% Cr3C2 as sintering additives, Ni3Al/TiC system composite of different compositions with fine mechanical and thermal properties were successfully fabricated by hot-press at 1300 -30MPa-120min, whose relative density reached above 95%.The mechanical and thermal properties of the prepared Ni3Al/TiC composites were measured. The results indicated that the physical properties of these materials were mainly dependent on the content of Ni3Al and increased obviously when 40vol% Ni3Al was contained since a net structure between Ni3Al phase and TiC grains were formed under the circumstances.