• The different ceramic phase distribution in TMCs was achieved by using LDED method in this work. • The high-temperature strength and plasticity were simultaneously improved in the TMC with intragranular uniform distribution of submicron-TiB. • The strength-plasticity synergy of TMC was attributed to the multi-scale interactions between the submicron-TiB and the Ti65 matrix alloy. • Early cracks at yield strain along TiB and TiC agglomeration during high-temperature tension in TMC were observed from in-situ tensile test. The Titanium Matrix Composite (TMC) can significantly improve high-temperature service performance, but it inevitably deteriorates strength-plasticity coordination. In this study, B 4 C and Ti65 alloy were used to fabricate TMCs with different ceramic phase distribution configurations by Laser Directed Energy Deposition (LDED), i.e., TMC1 with intragranular uniform distribution of submicron-TiB, and TMC2 with TiB and TiC agglomeration at the prior β grain boundaries. TMC1 exhibited a significantly better synergy of strength (660 MPa) and plasticity (55%) at 700 °C than the Ti65 matrix alloy, benefiting from multi-scale interactions between TiB and the α-Ti matrix. Firstly, the uniform distributed submicron-TiB created a multi-stage barrier to crack propagation. Secondly, the semi-coherent TiB/α interfaces simultaneously contributed to high strength and good plasticity via dislocation interaction. Furthermore, TiB can pin grain boundaries and suppress effectively high-temperature grain-boundary sliding. In contrast, the TiB and TiC aggregated at the grain boundaries intensify crack initiation and propagation, leading to lower plasticity in TMC2. These findings establish design criteria for tailoring reinforcement distribution in additively manufactured TMCs and provide guidance for developing high-performance, high-temperature structural materials.
Ma et al. (Sun,) studied this question.