Properties of carbon fiber reinforced titanium matrix composites by direct ink writing 3D Printing

The aligned short carbon fiber reinforced titanium matrix composites with the carbon fiber mass fractions ranging from 0.3% to 0.9% were fabricated by direct-write 3D printing combined with hot-pressing sintering. The rheological properties of composite slurries and the effects of carbon fiber content on the microstructure and mechanical performances of composites were systematically investigated. The results reveal that the viscosity and shear stress of composite slurries decrease with the increasing carbon fiber mass fraction. Carbon fibers are aligned along the printing direction under extrusion shear field, and the TiC interfacial coating layers form through the interfacial reaction between carbon fibers and Ti matrix during hot-pressing sintering. The tensile strength and yield strength of the composites first increase and then decline with fiber content rising, reaching the maximum values at carbon fiber mass fraction of 0.7%. By contrast, the hardness continuously increases while the elongation after fracture decreases monotonically. The evolution of mechanical properties is governed by the competitive mechanism among fiber directional strengthening, TiC interfacial strengthening, and the proliferation of pore defects at high fiber contents. The surface grooves generated by nitric acid etching and the in-situ formed TiC layers jointly construct a dual interfacial strengthening structure of mechanical interlocking plus metallurgical bonding, which guarantees the efficient load bearing of carbon fibers.