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

Abstract The influence of Zr content on microstructure and precipitation of silicide in as-cast Ti-1100- x Zr ( 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) 6 Si 3 (S 2 type) silicides. The TiSi and S 2 type silicides are found to precipitate heterogeneously in the retained β phase. The TiSi phase has specific orientation relationships with the retained β phase: 102 TiSi / / 1 1 ¯ 0 β , 2 ¯ 41 TiSi / / 001 β and (100) TiSi //(101) β , 0 1 ¯ 1 TiSi / / 1 ¯ 11 β . The long axis direction of S 2 type silicide has geometric connection with the direction of plates of α phase due to the orientation relationships between the S 2 phase and the α phase: 01 1 ¯ 0 S 2 / / 2 1 ¯ 1 ¯ 0 α , 2 1 ¯ 1 ¯ 3 S 2 / / 0001 α and 10 1 ¯ 0 S 2 / / 1 2 ¯ 10 α , 1 2 ¯ 13 S 2 / / 1 ¯ 011 α . It is also found that the Zr element added to titanium alloys affects the lattice parameters.