Research on the inhomogeneity and joint interface of in situ oriented TiBw/TA15 composites fabricated by vacuum hot-pressing sintering and canned extrusion

TiBw/TA15 composite bars with in situ synthesized TiBw were successfully manufactured by the hot-pressing sintering and subsequent hot canned extrusion. Microstructure evolution and mechanical behavior of as-sintered and as-extruded composites had been systematically investigated. After extrusion, due to the large deformation degree, significant grain refinement occurred and the long axes of whiskers were almost parallel to the extrusion direction. Almost no micro-voids were caused by the fractured TiBw as a consequence of three-dimensional compressive stress during the extrusion process. The mechanical properties results demonstrated that the ultimate tensile strength, elongation and Vickers hardness of the as-extruded composites all increased compared with that of the as-sintered composites. Moreover, there was an inhomogeneous microstructure in the as-extruded composites. The edge part possessed stronger grain refinement and much weaker texture than that of the central part owing to the different deformation degree. The interface between the titanium matrix composites and the capsule (45# steel) was relatively flat with no interfacial reaction, which showed the superiority of the 45# steel as the capsule for hot canned extrusion. Oxygen content result illustrated that there was no significant oxidation of titanium matrix during the sintering and extrusion process.