The influence of Zr content on microstructure and precipitation of silicide in as-cast near α titanium alloys

The influence of Zr content on microstructure and precipitation of silicide in as-cast Ti-1100-xZr (x = 4, 6 wt.%) alloys was systematically investigated. The results demonstrate that the addition of 6 wt.% Zr promotes the essential refinement of alloy microstructures and the formation of TiSi and ternary (TiZr)6Si3 (S2 type) silicides. The TiSi and S2 type silicides are found to precipitate heterogeneously in the retained β phase. The TiSi phase has specific orientation relationships with the retained β phase: 102TiSi//11¯0β, 2¯41TiSi//001β and (100)TiSi//(101)β, 01¯1TiSi//1¯11β. The long axis direction of S2 type silicide has geometric connection with the direction of plates of α phase due to the orientation relationships between the S2 phase and the α phase: 011¯0S2//21¯1¯0α, 21¯1¯3S2//0001α and 101¯0S2//12¯10α, 12¯13S2//1¯011α. It is also found that the Zr element added to titanium alloys affects the lattice parameters.