Ceramic-Reinforced γ-TiAl-Based Composites: Synthesis, Structure, and Properties

In this study, new multilayer TiAl-based composites were developed and characterized. The materials were produced by spark plasma sintering (SPS) of elemental Ti and Al foils and ceramic particles (TiB₂ and TiC) at 1250 °C. The matrix of the composites consisted of α₂-TiAl and γ-TiAl lamellas and reinforcing ceramic layers. Formation of the α₂ + γ structure, which occurred via a number of solid⁻liquid and solid⁻solid reactions and intermediate phases, was characterized by in situ synchrotron X-ray diffraction analysis. The combination of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis revealed that an interaction of TiC with Ti and Al led to the formation of a Ti₂AlC M_n+1AX_n (MAX) phase. No chemical reactions between TiB₂ and the matrix elements were observed. The microhardness, compressive strength, and creep behavior of the composites were measured to estimate their mechanical properties. The orientation of the layers with respect to the direction of the load affected the compressive strength and creep behavior of TiC-reinforced composites. The compressive strength of samples loaded in the perpendicular direction to layers was higher; however, the creep resistance was better for composites loaded in the longitudinal direction. The microhardness of the composites correlated with the microhardness of reinforcing components.