Effects of heat treatments on microstructure and tensile properties of as-extruded TiBw/near-α Ti composites

• Both Ti3Al and (TiZr)6Si3 can precipitate from matrix during aging treatment.
• After solution and aging treatment, (TiZr)6Si3 can be formed in grain body.
• Some precipitates prefer to form near the TiB whiskers.
• The strength of the as-aged composites increases to 760 MPa at 700 °C.

The effects of different heat treatments on the microstructure and tensile properties of the as-extruded TiBw/Ti60 composites have been investigated. Without solution treatment, the α2 phase precipitated from α phase and mounts of elliptical S2 silicide are formed at the interface of α/β phases after aging at 700 °C for 5 h, which results in clear enhancement of strength at 700–800 °C. After the solution and aging treatment, more α2 phase precipitates from αp phase and less spherical S2 silicide precipitated from the body of both αp and transformed β phase. Moreover, some small silicide precipitates are formed from α matrix near the TiBw due to the stacking faults and the interface effect. The TiBw are stable without any interfacial reaction during the heat treatments. The results show that the composites performed by solution and aging treatment exhibit high strength (1377 MPa) and low elongation (2%). The annealing treatment can soften the composites and increase the elongation to 7%.

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