Mechanical properties response of isotropic Ti2AlNb/TiAl interpenetrating phase composites with TPMS architectures prepared by laser powder bed fusion

TiAl alloys with high specific strength, excellent oxidation resistance and high-temperature performance are considered to replace nickel-based superalloys in the range of 700-800 degrees C. However, the low fracture toughness caused by the extremely high crack growth rate of TiAl alloys is still the biggest bottleneck restricting their development. Moreover, the anisotropy of continuous fibers and laminated structures reinforced composites is still present. In this study, a three-dimensional continuous Ti2AlNb reinforcement scaffold suitable for the strengthening and toughening of the TiAl alloys was designed, which provides a new idea for isotropic Ti2AlNb/ TiAl interpenetrating phase composites (IPCs) with high strength and toughness. Furthermore, the forming quality of the scaffolds prepared by laser powder bed fusion (L-PBF) was studied, and the anisotropy of L-PBF printed scaffolds was evaluated through the homogenization method and finite element simulation (FEA). What's more, the IPCs were prepared by vacuum hot press sintering (HPS). And the deformation-failure behaviors of scaffolds and their IPCs were analyzed by experimental and FE-simulated quasi-static compression tests. The results show that the equivalent diameter and number of pores for the triply periodic minimal surface (TPMS) structures are small, mostly distributed in 30-60 mu m with the volume fractions (VFs) of 0.14 %-0.26 %. The sheet-Gyroid (Gsh) and sheet-Split P (SPsh) exhibit excellent isotropy, followed by the sheet-Diamond (Dsh), while the skeleton-Gyroid (Gsk) and sheet-Primitive (Psh) show obvious anisotropy as the VF changes. The deviation between the maximum and minimum compressive strength values ranges from 1.7 % to 9.3 % for IPCs with a VF of 30 %, indicating that IPCs show good isotropy. The elastic modulus and yield strength of Gsh-IPCs are 15.8 % and 8.2 % higher than that of linear addition of TiAl matrix and Gsh scaffolds, respectively, which are contributed to three-dimensional interpenetrating structures composed of hard and soft phases, strong interfacial bonding as well as the specific TPMS structure.