Preparation of TiBw/Ti–6Al–4V composite with an inhomogeneous reinforced structure by a canned hot extrusion process

Abstract

The present study provided an efficient process combining pressureless sintering and subsequent canned hot extrusion to prepare a high-performance TiBw/Ti–6Al–4V composite with a columnar reinforced structure. Microstructure and mechanical performance for the as-extruded TiBw/Ti–6Al–4V composite was systematically investigated. The formation of TiB whiskers was significantly accelerated by the introduced high pressure and severe plastic deformation during the short canned extrusion compared to the pressureless sintering. With the development of highly preferred alignment of TiB whiskers along extrusion direction, a TiB columnar reinforced structure allied with a refined and irregular morphology in the Ti matrix was finally achieved in the as-extruded TiBw/Ti–6Al–4V composite. This led to a high relative density of ∼99.8% along with superior mechanical properties of ∼1282 MPa in ultimate tensile strength and ∼9.4% in fracture elongation at room temperature. Further investigation on high-temperature performance reveals that effective strengthening of the TiB columnar reinforced structure could be retained at 500 °C corresponding to the improved high-temperature strength over the as-extruded Ti–6Al–4V alloy by a 41% increase, but dramatically weakened at 600 °C related to the interface debonding between the TiB whiskers and the Ti matrix.