Effects of TiB Volume Fraction on the Microstructure and Mechanical Properties of TiBw/TA15 Composites with Novel Columnar Structure

To solve the problem of the inability to obtain plasticity and strength simultaneously in TMCs prepared through traditional powder metallurgy methods, TiBw/TA15 composites with columnar structure were designed and created which exhibited excellent comprehensive properties. The effects of TiB volume fraction on the microstructure and properties were further investigated to explore the upper limit of TiB volume fraction in TiBw/TA15 composites. The upper limit of TiB volume fraction was firstly obtained by theoretical calculation and then verified by experiment. The results showed that with the increase of TiB volume fraction, the microstructure of TiBw/TA15 composites changed from widmanstätten structure to bi-modal structure, the amount of equiaxed α increased, and the α colonies coarsened. The strength and hardness increased with the increase of TiBw, but the plasticity was opposite. When the TiB volume fraction exceeded the upper limit of the theoretically calculated value (6.7 vol.%), there was residual TiB₂ in the composites which would lead to sharply deteriorated performance.