TiB Whisker and Nitrogen Solid‐Solution Synergistic‐Strengthened Titanium Matrix Composites by Ti–BN via Spark Plasma Sintering and Hot Extrusion

Abstract

TiB whisker (TiBw) and nitrogen (N) solid‐solution synergistic‐strengthened titanium matrix composites (TMCs) are prepared by in situ reaction of Ti–BN system via spark plasma sintering (SPS) and hot extrusion. The effects of the in situ‐synthesized TiBw and N solid solution on the microstructure and mechanical properties of TMCs are studied. Results show that TiBw is broken into several short fragments and distributed parallel to the extrusion direction after hot extrusion, whereas N atoms are all dissolved into the Ti matrix. The BN additive dispersion method and hot extrusion process can greatly eliminate TiBw aggregates and reduce the mean size of TiBw. Tensile test results reveal that the Ti with only 0.4 wt.% BN exhibits an exceptional ultimate tensile strength of 879 MPa and 16.6% elongation at room temperature. On this basis, the main strengthening mechanism of TiBw reinforcement and N solid solution at room and high temperature are studied based on the Hall–Petch equation, load transfer mechanism, and Labusch model.

Design of In Situ Metal Matrix Composites Produced by Powder Metallurgy—A Critical Review

“…For instance, Pan et al [34], Otte [35,36], and Toptan [37] used Ti + BN for in situ formation of TiB reinforcements. No TiN can be found in any of the manufactured composites, because although titanium nitride is a very stable compound, nitrogen has very high solubility in Ti.…”