Densification of Ti/HA functionally graded material (FGM) by SPS

Abstract

Composites of hydroxyaptite (HA) and titanium (Ti) decompose for few days. The composite prepared from titanium hydride (TiH) and HA is stable for more than a year, but its toughness is very low. Functionally graded materials (FGMs) fabricated from TiH and HA by SPS cracked in the HA layer by the residual stress due to thermal expansion mismatch between Ti and HA and due to the higher relative density of the HA layer. A nitrided titanium (Ti(N)) was synthesized in N2 gas at 800 °C for 180 min, which formed a stable composite with HA. The Ti(N)/HA FGM free from crack was fabricated at 900 °C, which includes pores in the layer of Ti(N). The sintering temperature of 900 °C was low for the densification of the Ti(N) layer. A dense Ti/HA FGM was fabricated with layers of Ti, Ti(N), 80vol%Ti(N)-20vol%HA, 60vol%Ti(N)-40vol%HA and 40vol%Ti(N)-60vol%HA.