Effect of TiB2 content on the characteristics of spark plasma sintered Ti-TiBw composites

摘要

Spark plasma sintering (SPS) was employed to fabricate monolithic titanium and in-situ formed TiB whisker (TiBw) reinforced titanium matrix composites (TMCs) by adding different amounts of TiB2 as boron source. The sintering process was completed at 1050 degrees C for 5 min under 50 MPa. The influences of TiB2 content (0.6-9.6 wt. ) on microstructural evolution and mechanical properties of TMCs were investigated. Thermodynamics, XRD analysis and microstructural investigations confirmed the in-situ formation of TiBw in the composite samples. However, some semi-reacted TiB2 phases, surrounded by TiB coronas, were remained in the microstructure due to the unfinished chemical reaction between the components during a short-time sintering process. The results showed that all samples were appropriately densified by SPS process into the almost dense parts with relative density no less than 97.5. While bending strength decreased and hardness increased with increasing TiB2 content, the sample with 4.8 wt. TiB2 had the maximum tensile strength. Fractographical assessments showed that the addition of TiB2 hindered the grain growth of titanium matrix. With increasing TiB2 content, fracture mode changed from a multiple pattern to a predominantly transgranular and brittle state. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.