In-situ synthesized multi-component particle reinforced TiAl composite with excellent mechanical properties

Abstract

In order to overcome the inherent trade-off between strength and ductility of TiAl alloys, the BN nanosheets were added in Ti-48Al-2Cr-2Nb alloy. Ti-48Al-2Cr-2Nb-xBN (x = 0, 0.1, 0.5, 1, 2 wt%) alloys were prepared by vacuum arc melting (VAR), and the microstructures displayed a fully lamellar structure accompanied by simultaneous precipitation of Ti2AlN and TiB2 phases. The reaction of BN nanosheets with the Ti and Al elements resulted in formation of Ti2AlN and TiB2 phases. The lamellar colony size of TiAl composites was refined from 276.7 to 29.4 µm with BN content increasing from 0 to 2 wt%. While the lamellar spacing displayed an initial decrease followed by an increase, which was attributed to the synergistic effect of Ti2AlN and TiB2. Room temperature compression results showed that the compressive strength surged from 1653 to 2272 MPa as BN content rose from 0 to 0.5 wt%, with the highest compression strain of 34.7 % at 0.5 wt% BN. The high temperature compression results showed that the compressive strength increased from 887 to 1399 MPa as the BN content increasing from 0 to 1 wt%. Crack extension took the form of both trans-granular and inter-granular modes. The strengthening effect of TiAl composites was attributed to grain refinement strengthening and secondary phase strengthening via Ti2AlN and TiB2.