Multilayered heterogeneous titanium matrix composites based on in-situ reaction fabricated by selective laser melting: Microstructure and mechanical properties under different strain rates

Abstract

Multilayer heterogeneous titanium matrix composites (MHTMCs) based on in-situ reaction between Ti6Al4V and TiB2 were successfully fabricated by selective laser melting (SLM). The microstructure and mechanical properties under various strain rates were characterized by a combination of several methods in detail. Ti6Al4V layers and TMC layers exhibited alternate distribution in MHTMCs, both of which were mainly composed of α′-Ti with high aspect ratio due to the high cooling rate of the molten pool during SLM, and the in-situ TiB effectively refined the α′ laths in the TMC layers. The tensile strength and elongation of the MHTMCs reached 1406 MPa and 6.03 % respectively, and the enhancement of strength of the MHTMCs were mainly attributed to the synergistic effect of grain refinement strengthening, dispersion strengthening and hetero-deformation induced (HDI) strengthening. Under high strain rates, the MHTMCs exhibits significant strain rate hardening effect, and the fragmentation of α′ laths and intensive dislocation pile-up occurred during the dynamic deformation.