抄録
A pseudo-HIP technique combined with self-propagating high-temperature synthesis (SHS) has been studied for synthesis and consolidation of titanium aluminides, starting from compacts of mixtures of elemental powders of titanium and aluminum. The environmental pressure applied by the pseudo-HIP is effective to prevent swelling and dimensional change during the SHS reaction, resulting in high density in consolidated products. Density increases with the increase in applied pressure and 92% of theoretical density is stably achieved over a pressure of 45MPa. The volume of open pores remaining in consolidated products reduces rapidly with the increase in pressure; for example, the volume fraction of open pores is 2.7% in a Ti-47at%Al aluminide reaction-synthesized under a pressure of 45MPa and this value is about one eighth of that in a sample reaction-synthesized without any pressure. The volume of closed pores remaining, however, is scarcely affected with pressure, keeping a volume fraction of about 10%. Non-equilibrium phases remaining in as-reaction-synthesized products can be changed into the equilibrium phases without any dimensional change of the products by annealing them at 1273K for an hour, and the consolidated samples show good ductility in compression tests at elevated temperatures above 1273K.
