Microstructure and Properties of 3.5 vol.% TiBw/T16A14V Composite Tubes Fabricated by Hot-hydrostatic Extrusion

Tubes of 3.5 vol.% TiB whiskers reinforced Ti6AI4V matrix composites (TiBwiTi6A14V) were successfully fabricated by a two-step hot-hydrostatic extrusion process: beta extrusion at 1100 degrees C and subsequent near-0 extrusion at 950 degrees C. The dimensions of tubes were about 7 mm in diameter and 2 mm in thickness. A refined basket-weave structure in Ti6AI4V matrix was achieved at ambient temperature after the extrusion process. Besides, the original network structure formed by TiB whiskers synthesized was broken, while the TiB whiskers were preferentially aligned in the extruding direction. Meanwhile, a fibrous texture was evolved finally, resulting from partial dynamic recrystallization during the beta extrusion and the involvement of a phase during the near-beta extrusion. The tensile and compressive tests results showed that both the strength and ductility of the tubes were significantly improved. In particular, the tubes exhibited good mechanical properties at elevated temperatures.