Pseudo-HIP Combustion Synthesis of FeAl-TiB2 Composites

Abstract

FeAl-TiB2 composites have been produced from iron, aluminum, titanium and boron powders using the pseudo-HIP combustion synthesis process. The effects of TiB 2 volume fraction and preheating conditions such as time, temperature and pressure on the TiB2 particle size and porosity in the synthesized composites were investigated. When the mixtures of the elemental powders were heated, sudden and rapid temperature rise was always observed at temperatures near the melting point of aluminum, and the powder mixtures were melted. X-ray diffraction analyses revealed that the reaction products consisted of only FeAl and TiB 2 . Based on metallographic investigations and electron probe microanalyses, it was found that fine TiB 2 particle dispersed FeAl-based composites were synthesized by the above-mentioned exothermic reaction, although the composites included a lot of pores. The use of pseudo-isostatic pressure during the exothermic reaction brought about dramatic reduction in porosity. When the volume fraction of the TiB 2 particles increased, their average diameter also increased. The increase in volume fraction of the TiB 2 particles brought about the increase in the Vickers hardness and the volume fraction of pores. The volume fraction of pores was markedly reduced by preheating the powder mixture in vacuum. The preheating also reduced the TiB2 size. The application of pressure during the preheating brought about most significant reduction in TiB 2 size and the effect of preheating temperature was more significant than that of preheating time.