Reinforcements stimulated dynamic recrystallization behavior and tensile properties of extruded (TiB + TiC + La2O3)/Ti6Al4V composites

TiB, TiC and La2O3 multiple-reinforced Ti6Al4V matrix composites were successfully fabricated by common casting based on the in situ reaction of Ti, B4C, LaB6, and oxygen in the raw materials and forged subsequently. Hot extrusion was carried out on the as-forged composites to investigate its effect on microstructure and tensile properties of Ti6Al4V composites reinforced by low volume fraction of reinforcements. The microstructure showed that the TiBw and TiCp distributed homogeneously and the clustered reinforcements disappeared after hot extrusion. Besides, TiBw exhibited favorable alignment, rotating parallel to the extrusion direction and TiCp also distributed along the same direction. Moreover, the microstructure of as-extruded composites tended to formed two kind of microstructure zones: finer basket-weave zones containing few reinforcements, and equiaxial zones embedded with abundant reinforcements, which indicated that reinforcements stimulated dynamic recrystallization during hot extrusion. The tensile test results revealed that the hot extrusion can significantly improve the ductility of (TiB + TiC + La2O3)/Ti6Al4V composites accompanied by slight decrease of tensile strength, among which the 1.5 vol% (TiB + TiC + La2O3)/Ti6Al4V increased by nearly four times from 2.71% to 13.2% With ultimate strength decreasing by 8.5%. from 954 MPa to 903 MPa, compared with that of the as-forged composites. (C) 2017 Elsevier B.V. All rights reserved.