Effects of pre-sintering on microstructure and properties of TiBw/Ti6Al4V composites fabricated by hot extrusion with steel cup

In situ synthesized TiB whisker reinforced 3.5 vol% TiBw/Ti6Al4V composites have been synthesized by pre-sintering and hot extrusion with steel cup processes. The effects of pre-sintering temperature and time on densification behavior and mechanical properties of the as-extruded composites were investigated. The results indicated that as-extruded TiBw/Ti64 composite sintered at 1100 degrees C had the highest relative density of 99.4% along with ultimate tensile strength of 1352 MPa and elongation of 4.72%. With increasing pre-sintering temperature from 900 to 1100 degrees C, the in situ synthesized TiB whiskers which construct a quasi-continuous network microstructure produced by pre-sintering and hot extrusion techniques grow rapidly, while the relative density of the composites increases obviously. At the same time, the fracture type changes from brittle fracture to the hybrid-fracture characteristic of plastic fracture and brittle fracture. The strengthening effects can attribute to the matrix refine and the in-situ reaction TiB whiskers reinforcement due to pre-sintering and hot extrusion plastic deformation. The results also suggest that the optimal pre-sintering and hot extrusion with steel cup techniques are sintered at 1100 degrees C for 1 h in consideration of the comprehensive properties and the cost. (C) 2015 Elsevier B.V. All rights reserved.