Effect of Ultra-Rapid Heating/Cooling on the Microstructure and Properties of TC4-B-Si Titanium Matrix Composites

Titanium matrix composites (TMCs) possess excellent properties, which are widely applied in various high-end fields. An ultrafine multi-scale network structure may further enhance the TMCs. Then, the application potential is widened. Here, the in situ synthesized TC4-B-Si composites were prepared by selective laser melting technology, to achieve ultrafine microstructure by inducing ultra-rapid heating/cooling process. The preparation process–structure–performance relationships were investigated. It was found that an appropriate laser energy density leads to high-density TMCs with stable molten pools and good interlayer bonding. With the decreasing energy density, the in situ generated TiB network structure is refined from the sub-micron scale to the nano-scale. The most Si atoms are supersaturated solid-dissolved in the titanium matrix. In addition, the TiB distribution becomes heterogeneous. Due to the co-effect of grain refinement and reinforcement distribution, the microhardness shows a rising and then falling trend, with decreasing energy density. With a good balance of these two factors, the maximum value of microhardness reaches 454 HV. Therefore, controlling process parameters is a feasible way to achieve multi-structures, and thus enhanced properties. This method is expected to be used on various lightweight and wear-resistant structural components.