Precipitation Process of The New Intermetallic γ1 Phase in Ti-Al-Nb Ternary System

摘要

High Nb containing TiAl alloys are often cited as a kind of prospective lightweight material for high temperature application. The novel intermetallic phase γ1(Ti4Nb3Al9), which formed from γ-TiAl phase,could elevate the service temperature. The development of new lightweight Ti-Al-Nb alloys having higher service temperature than high Nb containing TiAl alloys becomes possible. This paper investigated the effect of heat treatment on the precipitation of the γ1 phase in Nb-TiAl based intermetallic alloys. The results showed that as for nominal composition of γ1 alloy the homogenization temperature should be up to 1400°C. γ1 phase precipitates from the y phase matrix during the following furnace cooling process. Higher Nb and Al contents are favorable for the precipitation of γ1 phase. After appropriate heat treatment γ1 phase could form from the alloys with nominal composition of Ti53Al-(16-26)Nb,Ti-55Al-(22-28)Nb,Ti-56Al-(16-25)Nb(all at%). The angle between γ1 phases is about 120°,so in terms of morphologic characteristics the classical full lamellar(FL) is not favorable for the precipitation of γ1.